From 8fc1c74765a2a8af2d71556e9d7a08b8fc9bdc2d Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Mon, 13 Jun 2022 14:12:34 -0700
Subject: [PATCH 01/25] Add the aggtor package

---
 sdk/metric/internal/aggtor/aggregation.go | 106 ++++++++++++++++++++++
 sdk/metric/internal/aggtor/aggregator.go  |  24 +++++
 sdk/metric/internal/aggtor/doc.go         |  20 ++++
 sdk/metric/internal/aggtor/drop.go        |  29 ++++++
 sdk/metric/internal/aggtor/histogram.go   |  40 ++++++++
 sdk/metric/internal/aggtor/lastvalue.go   |  39 ++++++++
 sdk/metric/internal/aggtor/number.go      |  87 ++++++++++++++++++
 sdk/metric/internal/aggtor/sum.go         |  40 ++++++++
 8 files changed, 385 insertions(+)
 create mode 100644 sdk/metric/internal/aggtor/aggregation.go
 create mode 100644 sdk/metric/internal/aggtor/aggregator.go
 create mode 100644 sdk/metric/internal/aggtor/doc.go
 create mode 100644 sdk/metric/internal/aggtor/drop.go
 create mode 100644 sdk/metric/internal/aggtor/histogram.go
 create mode 100644 sdk/metric/internal/aggtor/lastvalue.go
 create mode 100644 sdk/metric/internal/aggtor/number.go
 create mode 100644 sdk/metric/internal/aggtor/sum.go

diff --git a/sdk/metric/internal/aggtor/aggregation.go b/sdk/metric/internal/aggtor/aggregation.go
new file mode 100644
index 00000000000..fb722ea39b0
--- /dev/null
+++ b/sdk/metric/internal/aggtor/aggregation.go
@@ -0,0 +1,106 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+import (
+	"errors"
+	"fmt"
+)
+
+// Aggregation is a single data point in a timeseries that summarizes
+// measurements made during a time span.
+type Aggregation struct {
+	// Timestamp defines the time the last measurement was made. If zero, no
+	// measurements were made for this time span. The time is represented as a
+	// unix timestamp with nanosecond precision.
+	Timestamp uint64
+
+	// Value is the summarization of the measurements made.
+	Value value
+}
+
+var errIncompatible = errors.New("incompatible aggregation")
+
+// Fold combines other into a.
+func (a Aggregation) Fold(other Aggregation) error {
+	if other.Timestamp > a.Timestamp {
+		a.Timestamp = other.Timestamp
+	}
+	return a.Value.fold(other.Value)
+}
+
+type value interface {
+	// fold combines other into the value. It will return an errIncompatible
+	// if other is not a compatible type with value.
+	fold(other value) error
+}
+
+// SingleValue summarizes a set of measurements as a single numeric value.
+type SingleValue[N int64 | float64] struct {
+	Value N
+}
+
+func (v SingleValue[N]) fold(other value) error {
+	o, ok := other.(SingleValue[N])
+	if !ok {
+		return fmt.Errorf("%w: value types %T and %T", errIncompatible, v, other)
+	}
+	v.Value += o.Value
+	return nil
+}
+
+// HistogramValue summarizes a set of measurements as a histogram.
+type HistogramValue struct {
+	Bounds   []float64
+	Counts   []uint64
+	Sum      float64
+	Min, Max float64
+}
+
+func (v HistogramValue) fold(other value) error {
+	o, ok := other.(HistogramValue)
+	if !ok {
+		return fmt.Errorf("%w: value types %T and %T", errIncompatible, v, other)
+	}
+	if !sliceEqual[float64](v.Bounds, o.Bounds) || len(o.Counts) != len(v.Counts) {
+		return fmt.Errorf("%w: different histogram binning", errIncompatible)
+	}
+	v.Sum += o.Sum
+	for i, c := range o.Counts {
+		v.Counts[i] += c
+	}
+	if o.Min < v.Min {
+		v.Min = o.Min
+	}
+	if o.Max > v.Max {
+		v.Max = o.Max
+	}
+	return nil
+}
+
+func sliceEqual[T comparable](a, b []T) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i, v := range a {
+		if v != b[i] {
+			return false
+		}
+	}
+	return true
+}
diff --git a/sdk/metric/internal/aggtor/aggregator.go b/sdk/metric/internal/aggtor/aggregator.go
new file mode 100644
index 00000000000..576424f1f2e
--- /dev/null
+++ b/sdk/metric/internal/aggtor/aggregator.go
@@ -0,0 +1,24 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+// Aggregator forms an aggregation from a collection of recorded measurements.
+type Aggregator[N int64 | float64] interface {
+	Record(value N)
+	Aggregate() Aggregation
+}
diff --git a/sdk/metric/internal/aggtor/doc.go b/sdk/metric/internal/aggtor/doc.go
new file mode 100644
index 00000000000..77b97fb7c13
--- /dev/null
+++ b/sdk/metric/internal/aggtor/doc.go
@@ -0,0 +1,20 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+// Package aggtor provides types and functionality to accumulate and aggregate
+// measurements.
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
diff --git a/sdk/metric/internal/aggtor/drop.go b/sdk/metric/internal/aggtor/drop.go
new file mode 100644
index 00000000000..f37169ac173
--- /dev/null
+++ b/sdk/metric/internal/aggtor/drop.go
@@ -0,0 +1,29 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+// dropAgg drops all recorded data and returns an empty Aggregation.
+type dropAgg[N int64 | float64] struct{}
+
+// NewDrop returns an Aggregator that drops all recorded data and returns an
+// empty Aggregation.
+func NewDrop[N int64 | float64]() Aggregator[N] { return &dropAgg[N]{} }
+
+func (s *dropAgg[N]) Record(value N) {}
+
+func (s *dropAgg[N]) Aggregate() Aggregation { return Aggregation{} }
diff --git a/sdk/metric/internal/aggtor/histogram.go b/sdk/metric/internal/aggtor/histogram.go
new file mode 100644
index 00000000000..ee1f6dbe6b2
--- /dev/null
+++ b/sdk/metric/internal/aggtor/histogram.go
@@ -0,0 +1,40 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+// histogramAgg summarizes a set of measurements as an histogram with
+// explicitly defined buckets.
+type histogramAgg[N int64 | float64] struct {
+	// TODO: implement.
+}
+
+// NewHistogram returns an Aggregator that summarizes a set of measurements as
+// an histogram. The zero value will be used as the start value for all the
+// buckets of new Aggregations.
+func NewHistogram[N int64 | float64](zero Number[N], bounds []float64, recordMinMax bool) Aggregator[N] {
+	return &histogramAgg[N]{}
+}
+
+func (s *histogramAgg[N]) Record(value N) {
+	// TODO: implement.
+}
+
+func (s *histogramAgg[N]) Aggregate() Aggregation {
+	// TODO: implement.
+	return Aggregation{Value: HistogramValue{ /* TODO: calculate. */ }}
+}
diff --git a/sdk/metric/internal/aggtor/lastvalue.go b/sdk/metric/internal/aggtor/lastvalue.go
new file mode 100644
index 00000000000..ef7fac60f9b
--- /dev/null
+++ b/sdk/metric/internal/aggtor/lastvalue.go
@@ -0,0 +1,39 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+// lastValueAgg summarizes a set of measurements as the last one made.
+type lastValueAgg[N int64 | float64] struct {
+	// TODO: implement.
+}
+
+// NewLastValue returns an Aggregator that summarizes a set of measurements as
+// the last one made. The zero value will be used as the start value for all
+// new Aggregations.
+func NewLastValue[N int64 | float64](zero Number[N]) Aggregator[N] {
+	return &lastValueAgg[N]{}
+}
+
+func (s *lastValueAgg[N]) Record(value N) {
+	// TODO: implement.
+}
+
+func (s *lastValueAgg[N]) Aggregate() Aggregation {
+	// TODO: implement.
+	return Aggregation{Value: SingleValue[N]{ /* TODO: calculate */ }}
+}
diff --git a/sdk/metric/internal/aggtor/number.go b/sdk/metric/internal/aggtor/number.go
new file mode 100644
index 00000000000..99cc6c9c291
--- /dev/null
+++ b/sdk/metric/internal/aggtor/number.go
@@ -0,0 +1,87 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+import (
+	"math"
+	"sync/atomic"
+)
+
+type Number[N int64 | float64] interface {
+	// Store value atomically.
+	Store(value N)
+
+	// Add value atomically.
+	Add(value N)
+
+	// Load returns the stored value.
+	Load() N
+
+	// Clone creates a new Number from the current value.
+	Clone() Number[N]
+}
+
+type Int64 struct {
+	value *int64
+}
+
+var _ Number[int64] = Int64{}
+
+func NewInt64(v int64) Int64 {
+	return Int64{value: &v}
+}
+
+func (v Int64) Store(value int64) { atomic.StoreInt64(v.value, value) }
+func (v Int64) Add(value int64)   { atomic.AddInt64(v.value, value) }
+func (v Int64) Load() int64       { return atomic.LoadInt64(v.value) }
+func (v Int64) Clone() Number[int64] {
+	return NewInt64(v.Load())
+}
+
+type Float64 struct {
+	value *uint64
+}
+
+var _ Number[float64] = Float64{}
+
+func NewFloat64(v float64) Float64 {
+	u := math.Float64bits(v)
+	return Float64{value: &u}
+}
+
+func (v Float64) Store(value float64) {
+	atomic.StoreUint64(v.value, math.Float64bits(value))
+}
+
+func (v Float64) Add(value float64) {
+	for {
+		old := atomic.LoadUint64(v.value)
+		sum := math.Float64bits(math.Float64frombits(old) + value)
+		if atomic.CompareAndSwapUint64(v.value, old, sum) {
+			return
+		}
+	}
+}
+
+func (v Float64) Load() float64 {
+	return math.Float64frombits(atomic.LoadUint64(v.value))
+}
+
+func (v Float64) Clone() Number[float64] {
+	return NewFloat64(v.Load())
+}
diff --git a/sdk/metric/internal/aggtor/sum.go b/sdk/metric/internal/aggtor/sum.go
new file mode 100644
index 00000000000..67e9f926430
--- /dev/null
+++ b/sdk/metric/internal/aggtor/sum.go
@@ -0,0 +1,40 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+
+// sumAgg summarizes a set of measurements as their arithmetic sum.
+type sumAgg[N int64 | float64] struct {
+	// TODO: implement.
+}
+
+// NewSum returns an Aggregator that summarizes a set of
+// measurements as their arithmetic sum. The zero value will be used as the
+// start value for all new Aggregations.
+func NewSum[N int64 | float64](zero Number[N]) Aggregator[N] {
+	// TODO: implement.
+	return &sumAgg[N]{}
+}
+
+func (s *sumAgg[N]) Record(value N) {
+	// TODO: implement.
+}
+
+func (s *sumAgg[N]) Aggregate() Aggregation {
+	// TODO: implement.
+	return Aggregation{Value: SingleValue[N]{ /* TODO: calculate */ }}
+}

From dc1d912728de74feff3cdb5c8ee59b37ccebfd78 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Mon, 13 Jun 2022 14:16:49 -0700
Subject: [PATCH 02/25] Restrict to Go 1.18

---
 sdk/metric/config.go               | 4 ++--
 sdk/metric/config_test.go          | 4 ++--
 sdk/metric/export/data.go          | 4 ++--
 sdk/metric/exporter.go             | 4 ++--
 sdk/metric/go.mod                  | 2 +-
 sdk/metric/go.sum                  | 1 -
 sdk/metric/instrumentkind.go       | 4 ++--
 sdk/metric/manual_reader.go        | 4 ++--
 sdk/metric/manual_reader_test.go   | 4 ++--
 sdk/metric/meter.go                | 4 ++--
 sdk/metric/meter_test.go           | 4 ++--
 sdk/metric/periodic_reader.go      | 4 ++--
 sdk/metric/periodic_reader_test.go | 4 ++--
 sdk/metric/provider.go             | 4 ++--
 sdk/metric/provider_test.go        | 4 ++--
 sdk/metric/reader.go               | 4 ++--
 sdk/metric/reader_test.go          | 4 ++--
 sdk/metric/temporality.go          | 4 ++--
 sdk/metric/view/instrument.go      | 4 ++--
 sdk/metric/view/view.go            | 4 ++--
 20 files changed, 37 insertions(+), 38 deletions(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 258526dbe3a..fcf7024ab95 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index c2b91e8f559..bad1df033be 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric
 
diff --git a/sdk/metric/export/data.go b/sdk/metric/export/data.go
index 750294b2218..9ac934d5390 100644
--- a/sdk/metric/export/data.go
+++ b/sdk/metric/export/data.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 // TODO: NOTE this is a temporary space, it may be moved following the
 // discussion of #2813, or #2841
diff --git a/sdk/metric/exporter.go b/sdk/metric/exporter.go
index 52f39292555..d62838c9b15 100644
--- a/sdk/metric/exporter.go
+++ b/sdk/metric/exporter.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/go.mod b/sdk/metric/go.mod
index 07226ebfd9e..77e8d8111b9 100644
--- a/sdk/metric/go.mod
+++ b/sdk/metric/go.mod
@@ -1,6 +1,6 @@
 module go.opentelemetry.io/otel/sdk/metric
 
-go 1.17
+go 1.18
 
 require (
 	github.com/go-logr/logr v1.2.3
diff --git a/sdk/metric/go.sum b/sdk/metric/go.sum
index ac3360c6fee..2e2aed63d24 100644
--- a/sdk/metric/go.sum
+++ b/sdk/metric/go.sum
@@ -6,7 +6,6 @@ github.com/go-logr/logr v1.2.3/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbV
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
 github.com/google/go-cmp v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
-github.com/google/go-cmp v0.5.8/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
diff --git a/sdk/metric/instrumentkind.go b/sdk/metric/instrumentkind.go
index 8174eee5ef3..20d94fcc43a 100644
--- a/sdk/metric/instrumentkind.go
+++ b/sdk/metric/instrumentkind.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/manual_reader.go b/sdk/metric/manual_reader.go
index 97a11dfdfcd..636db3d982c 100644
--- a/sdk/metric/manual_reader.go
+++ b/sdk/metric/manual_reader.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/manual_reader_test.go b/sdk/metric/manual_reader_test.go
index 61b9ec74291..14c5d0765f3 100644
--- a/sdk/metric/manual_reader_test.go
+++ b/sdk/metric/manual_reader_test.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric/reader"
 
diff --git a/sdk/metric/meter.go b/sdk/metric/meter.go
index 3b052ae864e..daf892dd1dc 100644
--- a/sdk/metric/meter.go
+++ b/sdk/metric/meter.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/meter_test.go b/sdk/metric/meter_test.go
index 3fdfbdcb344..38aa7ae28d9 100644
--- a/sdk/metric/meter_test.go
+++ b/sdk/metric/meter_test.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric
 
diff --git a/sdk/metric/periodic_reader.go b/sdk/metric/periodic_reader.go
index 83ef273a341..55f1a2b8999 100644
--- a/sdk/metric/periodic_reader.go
+++ b/sdk/metric/periodic_reader.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/periodic_reader_test.go b/sdk/metric/periodic_reader_test.go
index ae5e40f2a20..e33e28a26e7 100644
--- a/sdk/metric/periodic_reader_test.go
+++ b/sdk/metric/periodic_reader_test.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/provider.go b/sdk/metric/provider.go
index 8276d278f26..98d0faffc22 100644
--- a/sdk/metric/provider.go
+++ b/sdk/metric/provider.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/provider_test.go b/sdk/metric/provider_test.go
index dca401fe3b8..20eb60590a9 100644
--- a/sdk/metric/provider_test.go
+++ b/sdk/metric/provider_test.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric
 
diff --git a/sdk/metric/reader.go b/sdk/metric/reader.go
index 2af077bb4bf..0db7fcd255c 100644
--- a/sdk/metric/reader.go
+++ b/sdk/metric/reader.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/reader_test.go b/sdk/metric/reader_test.go
index cb6a1761805..b47493124a7 100644
--- a/sdk/metric/reader_test.go
+++ b/sdk/metric/reader_test.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric/reader"
 
diff --git a/sdk/metric/temporality.go b/sdk/metric/temporality.go
index 289b151606e..fa896748287 100644
--- a/sdk/metric/temporality.go
+++ b/sdk/metric/temporality.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
diff --git a/sdk/metric/view/instrument.go b/sdk/metric/view/instrument.go
index e0a7774b481..b17205c3ac4 100644
--- a/sdk/metric/view/instrument.go
+++ b/sdk/metric/view/instrument.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package view // import "go.opentelemetry.io/otel/sdk/metric/view"
 
diff --git a/sdk/metric/view/view.go b/sdk/metric/view/view.go
index f8190a3906a..7598ce15ab5 100644
--- a/sdk/metric/view/view.go
+++ b/sdk/metric/view/view.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.17
-// +build go1.17
+//go:build go1.18
+// +build go1.18
 
 package view // import "go.opentelemetry.io/otel/sdk/metric/view"
 

From f9e8a49170dfdae5d984e6c715faf8fe6d90233b Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Mon, 13 Jun 2022 19:42:59 -0700
Subject: [PATCH 03/25] Add missing build block to view_test.go

---
 sdk/metric/view/view_test.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sdk/metric/view/view_test.go b/sdk/metric/view/view_test.go
index ffd4095fea1..10696ff00a6 100644
--- a/sdk/metric/view/view_test.go
+++ b/sdk/metric/view/view_test.go
@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.18
+// +build go1.18
+
 package view
 
 import (

From 59df1f71458d972998e840886625a6526579a8eb Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Mon, 13 Jun 2022 19:45:06 -0700
Subject: [PATCH 04/25] Comment Aggregator iface

---
 sdk/metric/internal/aggtor/aggregator.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sdk/metric/internal/aggtor/aggregator.go b/sdk/metric/internal/aggtor/aggregator.go
index 576424f1f2e..7e5174ec360 100644
--- a/sdk/metric/internal/aggtor/aggregator.go
+++ b/sdk/metric/internal/aggtor/aggregator.go
@@ -19,6 +19,9 @@ package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
 // Aggregator forms an aggregation from a collection of recorded measurements.
 type Aggregator[N int64 | float64] interface {
+	// Record includes value in the aggregation.
 	Record(value N)
+
+	// Aggregate returns an aggregation of all recorded values.
 	Aggregate() Aggregation
 }

From 0a700fe596642a758df49eec3d61197fcfb113f0 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Mon, 13 Jun 2022 19:51:23 -0700
Subject: [PATCH 05/25] Use Go 1.18 as the default ci version

---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index da3fcf1b71f..aa2bd8d3fac 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ env:
   # Path to where test results will be saved.
   TEST_RESULTS: /tmp/test-results
   # Default minimum version of Go to support.
-  DEFAULT_GO_VERSION: 1.17
+  DEFAULT_GO_VERSION: 1.18
 jobs:
   lint:
     runs-on: ubuntu-latest

From a5c5834a939f825fc4e0b10a28b0a4ce249b19f9 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Wed, 15 Jun 2022 12:36:21 -0700
Subject: [PATCH 06/25] Update Aggregator iface from feedback

---
 sdk/metric/internal/aggtor/aggregation.go |  8 ++++++++
 sdk/metric/internal/aggtor/aggregator.go  | 10 ++++++----
 sdk/metric/internal/aggtor/doc.go         |  3 +--
 sdk/metric/internal/aggtor/drop.go        |  6 ++++--
 sdk/metric/internal/aggtor/histogram.go   | 12 +++++++++---
 sdk/metric/internal/aggtor/lastvalue.go   | 12 +++++++++---
 sdk/metric/internal/aggtor/sum.go         | 12 +++++++++---
 7 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/sdk/metric/internal/aggtor/aggregation.go b/sdk/metric/internal/aggtor/aggregation.go
index fb722ea39b0..8b038e5ccd7 100644
--- a/sdk/metric/internal/aggtor/aggregation.go
+++ b/sdk/metric/internal/aggtor/aggregation.go
@@ -20,6 +20,8 @@ package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 import (
 	"errors"
 	"fmt"
+
+	"go.opentelemetry.io/otel/attribute"
 )
 
 // Aggregation is a single data point in a timeseries that summarizes
@@ -30,6 +32,9 @@ type Aggregation struct {
 	// unix timestamp with nanosecond precision.
 	Timestamp uint64
 
+	// Attributes are the unique dimensions Value describes.
+	Attributes *attribute.Set
+
 	// Value is the summarization of the measurements made.
 	Value value
 }
@@ -41,6 +46,9 @@ func (a Aggregation) Fold(other Aggregation) error {
 	if other.Timestamp > a.Timestamp {
 		a.Timestamp = other.Timestamp
 	}
+	if !a.Attributes.Equals(other.Attributes) {
+		return fmt.Errorf("%w: attributes not equal", errIncompatible)
+	}
 	return a.Value.fold(other.Value)
 }
 
diff --git a/sdk/metric/internal/aggtor/aggregator.go b/sdk/metric/internal/aggtor/aggregator.go
index 7e5174ec360..32dd9a5f7d1 100644
--- a/sdk/metric/internal/aggtor/aggregator.go
+++ b/sdk/metric/internal/aggtor/aggregator.go
@@ -17,11 +17,13 @@
 
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
+import "go.opentelemetry.io/otel/attribute"
+
 // Aggregator forms an aggregation from a collection of recorded measurements.
 type Aggregator[N int64 | float64] interface {
-	// Record includes value in the aggregation.
-	Record(value N)
+	// Record includes value scoped by attr in the aggregation.
+	Record(value N, attr *attribute.Set)
 
-	// Aggregate returns an aggregation of all recorded values.
-	Aggregate() Aggregation
+	// Aggregate returns aggregations of all recorded values.
+	Aggregate() []Aggregation
 }
diff --git a/sdk/metric/internal/aggtor/doc.go b/sdk/metric/internal/aggtor/doc.go
index 77b97fb7c13..8690de1449c 100644
--- a/sdk/metric/internal/aggtor/doc.go
+++ b/sdk/metric/internal/aggtor/doc.go
@@ -15,6 +15,5 @@
 //go:build go1.18
 // +build go1.18
 
-// Package aggtor provides types and functionality to accumulate and aggregate
-// measurements.
+// Package aggtor provides types and functionality to aggregate measurements.
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
diff --git a/sdk/metric/internal/aggtor/drop.go b/sdk/metric/internal/aggtor/drop.go
index f37169ac173..8095d2ec404 100644
--- a/sdk/metric/internal/aggtor/drop.go
+++ b/sdk/metric/internal/aggtor/drop.go
@@ -17,6 +17,8 @@
 
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
+import "go.opentelemetry.io/otel/attribute"
+
 // dropAgg drops all recorded data and returns an empty Aggregation.
 type dropAgg[N int64 | float64] struct{}
 
@@ -24,6 +26,6 @@ type dropAgg[N int64 | float64] struct{}
 // empty Aggregation.
 func NewDrop[N int64 | float64]() Aggregator[N] { return &dropAgg[N]{} }
 
-func (s *dropAgg[N]) Record(value N) {}
+func (s *dropAgg[N]) Record(N, *attribute.Set) {}
 
-func (s *dropAgg[N]) Aggregate() Aggregation { return Aggregation{} }
+func (s *dropAgg[N]) Aggregate() []Aggregation { return nil }
diff --git a/sdk/metric/internal/aggtor/histogram.go b/sdk/metric/internal/aggtor/histogram.go
index ee1f6dbe6b2..e8ac2c83929 100644
--- a/sdk/metric/internal/aggtor/histogram.go
+++ b/sdk/metric/internal/aggtor/histogram.go
@@ -17,6 +17,8 @@
 
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
+import "go.opentelemetry.io/otel/attribute"
+
 // histogramAgg summarizes a set of measurements as an histogram with
 // explicitly defined buckets.
 type histogramAgg[N int64 | float64] struct {
@@ -30,11 +32,15 @@ func NewHistogram[N int64 | float64](zero Number[N], bounds []float64, recordMin
 	return &histogramAgg[N]{}
 }
 
-func (s *histogramAgg[N]) Record(value N) {
+func (s *histogramAgg[N]) Record(value N, attr *attribute.Set) {
 	// TODO: implement.
 }
 
-func (s *histogramAgg[N]) Aggregate() Aggregation {
+func (s *histogramAgg[N]) Aggregate() []Aggregation {
 	// TODO: implement.
-	return Aggregation{Value: HistogramValue{ /* TODO: calculate. */ }}
+	return []Aggregation{
+		{
+			Value: HistogramValue{ /* TODO: calculate. */ },
+		},
+	}
 }
diff --git a/sdk/metric/internal/aggtor/lastvalue.go b/sdk/metric/internal/aggtor/lastvalue.go
index ef7fac60f9b..dd9f8be1416 100644
--- a/sdk/metric/internal/aggtor/lastvalue.go
+++ b/sdk/metric/internal/aggtor/lastvalue.go
@@ -17,6 +17,8 @@
 
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
+import "go.opentelemetry.io/otel/attribute"
+
 // lastValueAgg summarizes a set of measurements as the last one made.
 type lastValueAgg[N int64 | float64] struct {
 	// TODO: implement.
@@ -29,11 +31,15 @@ func NewLastValue[N int64 | float64](zero Number[N]) Aggregator[N] {
 	return &lastValueAgg[N]{}
 }
 
-func (s *lastValueAgg[N]) Record(value N) {
+func (s *lastValueAgg[N]) Record(value N, attr *attribute.Set) {
 	// TODO: implement.
 }
 
-func (s *lastValueAgg[N]) Aggregate() Aggregation {
+func (s *lastValueAgg[N]) Aggregate() []Aggregation {
 	// TODO: implement.
-	return Aggregation{Value: SingleValue[N]{ /* TODO: calculate */ }}
+	return []Aggregation{
+		{
+			Value: SingleValue[N]{ /* TODO: calculate */ },
+		},
+	}
 }
diff --git a/sdk/metric/internal/aggtor/sum.go b/sdk/metric/internal/aggtor/sum.go
index 67e9f926430..3103b62de79 100644
--- a/sdk/metric/internal/aggtor/sum.go
+++ b/sdk/metric/internal/aggtor/sum.go
@@ -17,6 +17,8 @@
 
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
+import "go.opentelemetry.io/otel/attribute"
+
 // sumAgg summarizes a set of measurements as their arithmetic sum.
 type sumAgg[N int64 | float64] struct {
 	// TODO: implement.
@@ -30,11 +32,15 @@ func NewSum[N int64 | float64](zero Number[N]) Aggregator[N] {
 	return &sumAgg[N]{}
 }
 
-func (s *sumAgg[N]) Record(value N) {
+func (s *sumAgg[N]) Record(value N, attr *attribute.Set) {
 	// TODO: implement.
 }
 
-func (s *sumAgg[N]) Aggregate() Aggregation {
+func (s *sumAgg[N]) Aggregate() []Aggregation {
 	// TODO: implement.
-	return Aggregation{Value: SingleValue[N]{ /* TODO: calculate */ }}
+	return []Aggregation{
+		{
+			Value: SingleValue[N]{ /* TODO: calculate */ },
+		},
+	}
 }

From aa8b3012a474fc59f823a4c9300cde25a1c8e427 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 10:53:59 -0700
Subject: [PATCH 07/25] Accept hist conf

---
 sdk/metric/internal/aggtor/histogram.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/sdk/metric/internal/aggtor/histogram.go b/sdk/metric/internal/aggtor/histogram.go
index e8ac2c83929..239a1d94025 100644
--- a/sdk/metric/internal/aggtor/histogram.go
+++ b/sdk/metric/internal/aggtor/histogram.go
@@ -17,7 +17,10 @@
 
 package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
 
-import "go.opentelemetry.io/otel/attribute"
+import (
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
+)
 
 // histogramAgg summarizes a set of measurements as an histogram with
 // explicitly defined buckets.
@@ -28,7 +31,7 @@ type histogramAgg[N int64 | float64] struct {
 // NewHistogram returns an Aggregator that summarizes a set of measurements as
 // an histogram. The zero value will be used as the start value for all the
 // buckets of new Aggregations.
-func NewHistogram[N int64 | float64](zero Number[N], bounds []float64, recordMinMax bool) Aggregator[N] {
+func NewHistogram[N int64 | float64](zero Number[N], cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
 	return &histogramAgg[N]{}
 }
 

From f390e41c9a267980d39eec05b571cd88bfcbc671 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 10:58:03 -0700
Subject: [PATCH 08/25] Flatten aggtor into just internal

---
 sdk/metric/internal/{aggtor => }/aggregation.go | 2 +-
 sdk/metric/internal/{aggtor => }/aggregator.go  | 2 +-
 sdk/metric/internal/{aggtor => }/doc.go         | 6 ++++--
 sdk/metric/internal/{aggtor => }/drop.go        | 2 +-
 sdk/metric/internal/{aggtor => }/histogram.go   | 2 +-
 sdk/metric/internal/{aggtor => }/lastvalue.go   | 2 +-
 sdk/metric/internal/{aggtor => }/number.go      | 2 +-
 sdk/metric/internal/{aggtor => }/sum.go         | 2 +-
 8 files changed, 11 insertions(+), 9 deletions(-)
 rename sdk/metric/internal/{aggtor => }/aggregation.go (97%)
 rename sdk/metric/internal/{aggtor => }/aggregator.go (92%)
 rename sdk/metric/internal/{aggtor => }/doc.go (69%)
 rename sdk/metric/internal/{aggtor => }/drop.go (93%)
 rename sdk/metric/internal/{aggtor => }/histogram.go (94%)
 rename sdk/metric/internal/{aggtor => }/lastvalue.go (94%)
 rename sdk/metric/internal/{aggtor => }/number.go (96%)
 rename sdk/metric/internal/{aggtor => }/sum.go (94%)

diff --git a/sdk/metric/internal/aggtor/aggregation.go b/sdk/metric/internal/aggregation.go
similarity index 97%
rename from sdk/metric/internal/aggtor/aggregation.go
rename to sdk/metric/internal/aggregation.go
index 8b038e5ccd7..3e9d6cebfc8 100644
--- a/sdk/metric/internal/aggtor/aggregation.go
+++ b/sdk/metric/internal/aggregation.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import (
 	"errors"
diff --git a/sdk/metric/internal/aggtor/aggregator.go b/sdk/metric/internal/aggregator.go
similarity index 92%
rename from sdk/metric/internal/aggtor/aggregator.go
rename to sdk/metric/internal/aggregator.go
index 32dd9a5f7d1..64ab4d9a059 100644
--- a/sdk/metric/internal/aggtor/aggregator.go
+++ b/sdk/metric/internal/aggregator.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import "go.opentelemetry.io/otel/attribute"
 
diff --git a/sdk/metric/internal/aggtor/doc.go b/sdk/metric/internal/doc.go
similarity index 69%
rename from sdk/metric/internal/aggtor/doc.go
rename to sdk/metric/internal/doc.go
index 8690de1449c..059a38f5bd1 100644
--- a/sdk/metric/internal/aggtor/doc.go
+++ b/sdk/metric/internal/doc.go
@@ -15,5 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-// Package aggtor provides types and functionality to aggregate measurements.
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+// Package internal provides types and functionality used to aggregate and
+// cycle the state of metric measurements made by the SDK. These types and
+// functionality are meant only for internal SDK use.
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
diff --git a/sdk/metric/internal/aggtor/drop.go b/sdk/metric/internal/drop.go
similarity index 93%
rename from sdk/metric/internal/aggtor/drop.go
rename to sdk/metric/internal/drop.go
index 8095d2ec404..b145c3518c0 100644
--- a/sdk/metric/internal/aggtor/drop.go
+++ b/sdk/metric/internal/drop.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import "go.opentelemetry.io/otel/attribute"
 
diff --git a/sdk/metric/internal/aggtor/histogram.go b/sdk/metric/internal/histogram.go
similarity index 94%
rename from sdk/metric/internal/aggtor/histogram.go
rename to sdk/metric/internal/histogram.go
index 239a1d94025..bf64af2c42a 100644
--- a/sdk/metric/internal/aggtor/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import (
 	"go.opentelemetry.io/otel/attribute"
diff --git a/sdk/metric/internal/aggtor/lastvalue.go b/sdk/metric/internal/lastvalue.go
similarity index 94%
rename from sdk/metric/internal/aggtor/lastvalue.go
rename to sdk/metric/internal/lastvalue.go
index dd9f8be1416..cd7663e092a 100644
--- a/sdk/metric/internal/aggtor/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import "go.opentelemetry.io/otel/attribute"
 
diff --git a/sdk/metric/internal/aggtor/number.go b/sdk/metric/internal/number.go
similarity index 96%
rename from sdk/metric/internal/aggtor/number.go
rename to sdk/metric/internal/number.go
index 99cc6c9c291..a6f4654b323 100644
--- a/sdk/metric/internal/aggtor/number.go
+++ b/sdk/metric/internal/number.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import (
 	"math"
diff --git a/sdk/metric/internal/aggtor/sum.go b/sdk/metric/internal/sum.go
similarity index 94%
rename from sdk/metric/internal/aggtor/sum.go
rename to sdk/metric/internal/sum.go
index 3103b62de79..a57b0254e89 100644
--- a/sdk/metric/internal/aggtor/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -15,7 +15,7 @@
 //go:build go1.18
 // +build go1.18
 
-package aggtor // import "go.opentelemetry.io/otel/sdk/metric/internal/aggtor"
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import "go.opentelemetry.io/otel/attribute"
 

From 778c10aa3dac935ae2b3e1eb9e1cbf88dd161006 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 13:08:26 -0700
Subject: [PATCH 09/25] Add Cycler interface

Separate the duties of aggregation and maintaining state across
aggregation periods.
---
 sdk/metric/internal/aggregation.go |  3 ++
 sdk/metric/internal/aggregator.go  | 16 +++++--
 sdk/metric/internal/cycler.go      | 69 ++++++++++++++++++++++++++++++
 sdk/metric/internal/drop.go        |  4 +-
 sdk/metric/internal/histogram.go   |  4 +-
 sdk/metric/internal/lastvalue.go   |  4 +-
 sdk/metric/internal/sum.go         |  4 +-
 7 files changed, 92 insertions(+), 12 deletions(-)
 create mode 100644 sdk/metric/internal/cycler.go

diff --git a/sdk/metric/internal/aggregation.go b/sdk/metric/internal/aggregation.go
index 3e9d6cebfc8..414e2fa0505 100644
--- a/sdk/metric/internal/aggregation.go
+++ b/sdk/metric/internal/aggregation.go
@@ -27,6 +27,9 @@ import (
 // Aggregation is a single data point in a timeseries that summarizes
 // measurements made during a time span.
 type Aggregation struct {
+	// TODO: Replace this with the export.Aggregation type once #2961 is
+	// merged.
+
 	// Timestamp defines the time the last measurement was made. If zero, no
 	// measurements were made for this time span. The time is represented as a
 	// unix timestamp with nanosecond precision.
diff --git a/sdk/metric/internal/aggregator.go b/sdk/metric/internal/aggregator.go
index 64ab4d9a059..2f2b11dc83a 100644
--- a/sdk/metric/internal/aggregator.go
+++ b/sdk/metric/internal/aggregator.go
@@ -20,10 +20,18 @@ package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 import "go.opentelemetry.io/otel/attribute"
 
 // Aggregator forms an aggregation from a collection of recorded measurements.
+// Aggregators are use with Cyclers to collect and produce metrics from
+// instrument measurements. Aggregators handle the collection (and
+// aggregation) of measurements, while Cyclers handle how those aggregated
+// measurements are combined and then produced to the telemetry pipeline.
 type Aggregator[N int64 | float64] interface {
-	// Record includes value scoped by attr in the aggregation.
-	Record(value N, attr *attribute.Set)
+	// Aggregate records the measurement, scoped by attr, and aggregates it
+	// into an aggregation.
+	Aggregate(measurement N, attr *attribute.Set)
 
-	// Aggregate returns aggregations of all recorded values.
-	Aggregate() []Aggregation
+	// flush clears aggregations that have been recorded. The Aggregator
+	// resets itself for a new aggregation period when called, it does not
+	// carry forward any state. If aggregation periods need to be combined it
+	// is the callers responsibility to achieve this.
+	flush() []Aggregation
 }
diff --git a/sdk/metric/internal/cycler.go b/sdk/metric/internal/cycler.go
new file mode 100644
index 00000000000..599280f8c6c
--- /dev/null
+++ b/sdk/metric/internal/cycler.go
@@ -0,0 +1,69 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
+
+// Cycler cycles aggregation periods. It will handle any state and progression
+// of one period to the next based on the temporality of the cycling.
+type Cycler interface {
+	// Cycle returns an []Aggregation for the current period. If the cycler
+	// merges state from previous periods into the current, the []Aggregation
+	// returned reflects this.
+	Cycle() []Aggregation
+
+	// TODO: Replace the return type with []export.Aggregation once #2961 is
+	// merged.
+}
+
+// deltaCylcer cycles aggregation periods by returning the aggregation
+// produces from that period only. No state is maintained from one period to
+// the next.
+type deltaCylcer[N int64 | float64] struct {
+	aggregator Aggregator[N]
+}
+
+func NewDeltaCylcer[N int64 | float64](a Aggregator[N]) Cycler {
+	return deltaCylcer[N]{aggregator: a}
+}
+
+func (c deltaCylcer[N]) Cycle() []Aggregation {
+	return c.aggregator.flush()
+}
+
+// cumulativeCylcer cycles aggregation periods by returning the cumulative
+// aggregation from its start time until the current period.
+type cumulativeCylcer[N int64 | float64] struct {
+	// TODO: implement a cumulative storing field.
+	aggregator Aggregator[N]
+}
+
+func NewCumulativeCylcer[N int64 | float64](a Aggregator[N]) Cycler {
+	c := cumulativeCylcer[N]{aggregator: a}
+
+	// TODO: Initialize a new cumulative storage.
+
+	return c
+}
+
+func (c cumulativeCylcer[N]) Cycle() []Aggregation {
+	// TODO: Update cumulative storage of aggregations and return them.
+
+	// FIXME: currently this returns a delta representation of the
+	// aggregation. When the cumulative storage is complete it should return a
+	// cumulative representation.
+	return c.aggregator.flush()
+}
diff --git a/sdk/metric/internal/drop.go b/sdk/metric/internal/drop.go
index b145c3518c0..23d32676fba 100644
--- a/sdk/metric/internal/drop.go
+++ b/sdk/metric/internal/drop.go
@@ -26,6 +26,6 @@ type dropAgg[N int64 | float64] struct{}
 // empty Aggregation.
 func NewDrop[N int64 | float64]() Aggregator[N] { return &dropAgg[N]{} }
 
-func (s *dropAgg[N]) Record(N, *attribute.Set) {}
+func (s *dropAgg[N]) Aggregate(N, *attribute.Set) {}
 
-func (s *dropAgg[N]) Aggregate() []Aggregation { return nil }
+func (s *dropAgg[N]) flush() []Aggregation { return nil }
diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index bf64af2c42a..5c4fdd4c2e2 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -35,11 +35,11 @@ func NewHistogram[N int64 | float64](zero Number[N], cfg aggregation.ExplicitBuc
 	return &histogramAgg[N]{}
 }
 
-func (s *histogramAgg[N]) Record(value N, attr *attribute.Set) {
+func (s *histogramAgg[N]) Aggregate(value N, attr *attribute.Set) {
 	// TODO: implement.
 }
 
-func (s *histogramAgg[N]) Aggregate() []Aggregation {
+func (s *histogramAgg[N]) flush() []Aggregation {
 	// TODO: implement.
 	return []Aggregation{
 		{
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index cd7663e092a..1e49456c368 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -31,11 +31,11 @@ func NewLastValue[N int64 | float64](zero Number[N]) Aggregator[N] {
 	return &lastValueAgg[N]{}
 }
 
-func (s *lastValueAgg[N]) Record(value N, attr *attribute.Set) {
+func (s *lastValueAgg[N]) Aggregate(value N, attr *attribute.Set) {
 	// TODO: implement.
 }
 
-func (s *lastValueAgg[N]) Aggregate() []Aggregation {
+func (s *lastValueAgg[N]) flush() []Aggregation {
 	// TODO: implement.
 	return []Aggregation{
 		{
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index a57b0254e89..06702bd4c38 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -32,11 +32,11 @@ func NewSum[N int64 | float64](zero Number[N]) Aggregator[N] {
 	return &sumAgg[N]{}
 }
 
-func (s *sumAgg[N]) Record(value N, attr *attribute.Set) {
+func (s *sumAgg[N]) Aggregate(value N, attr *attribute.Set) {
 	// TODO: implement.
 }
 
-func (s *sumAgg[N]) Aggregate() []Aggregation {
+func (s *sumAgg[N]) flush() []Aggregation {
 	// TODO: implement.
 	return []Aggregation{
 		{

From bd9c9634e892469fa6984df6c6fa581aa4c49f28 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 13:09:51 -0700
Subject: [PATCH 10/25] Remove build flags for doc.go

---
 sdk/metric/internal/doc.go | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/sdk/metric/internal/doc.go b/sdk/metric/internal/doc.go
index 059a38f5bd1..e1aa11ab2e1 100644
--- a/sdk/metric/internal/doc.go
+++ b/sdk/metric/internal/doc.go
@@ -12,9 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.18
-// +build go1.18
-
 // Package internal provides types and functionality used to aggregate and
 // cycle the state of metric measurements made by the SDK. These types and
 // functionality are meant only for internal SDK use.

From 816f3dc491d87eb47f38a3dc64c75961ab8dba81 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 13:11:08 -0700
Subject: [PATCH 11/25] Clarify Cycler documentation

---
 sdk/metric/internal/cycler.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sdk/metric/internal/cycler.go b/sdk/metric/internal/cycler.go
index 599280f8c6c..d8bbaeae9cd 100644
--- a/sdk/metric/internal/cycler.go
+++ b/sdk/metric/internal/cycler.go
@@ -17,8 +17,8 @@
 
 package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
-// Cycler cycles aggregation periods. It will handle any state and progression
-// of one period to the next based on the temporality of the cycling.
+// Cycler cycles aggregation periods. It will handle any state progression
+// from one period to the next based on the temporality of the cycling.
 type Cycler interface {
 	// Cycle returns an []Aggregation for the current period. If the cycler
 	// merges state from previous periods into the current, the []Aggregation

From 0d7923c7506cc1b7ea16f0e2f6693034b5bc64eb Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 13:15:19 -0700
Subject: [PATCH 12/25] Remove aggregation fold logic

---
 sdk/metric/internal/aggregation.go | 64 ++----------------------------
 1 file changed, 4 insertions(+), 60 deletions(-)

diff --git a/sdk/metric/internal/aggregation.go b/sdk/metric/internal/aggregation.go
index 414e2fa0505..71ad88cbca3 100644
--- a/sdk/metric/internal/aggregation.go
+++ b/sdk/metric/internal/aggregation.go
@@ -18,9 +18,6 @@
 package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import (
-	"errors"
-	"fmt"
-
 	"go.opentelemetry.io/otel/attribute"
 )
 
@@ -42,38 +39,16 @@ type Aggregation struct {
 	Value value
 }
 
-var errIncompatible = errors.New("incompatible aggregation")
-
-// Fold combines other into a.
-func (a Aggregation) Fold(other Aggregation) error {
-	if other.Timestamp > a.Timestamp {
-		a.Timestamp = other.Timestamp
-	}
-	if !a.Attributes.Equals(other.Attributes) {
-		return fmt.Errorf("%w: attributes not equal", errIncompatible)
-	}
-	return a.Value.fold(other.Value)
-}
-
 type value interface {
-	// fold combines other into the value. It will return an errIncompatible
-	// if other is not a compatible type with value.
-	fold(other value) error
+	private()
 }
 
-// SingleValue summarizes a set of measurements as a single numeric value.
+// SingleValue summarizes a set of measurements as a single value.
 type SingleValue[N int64 | float64] struct {
 	Value N
 }
 
-func (v SingleValue[N]) fold(other value) error {
-	o, ok := other.(SingleValue[N])
-	if !ok {
-		return fmt.Errorf("%w: value types %T and %T", errIncompatible, v, other)
-	}
-	v.Value += o.Value
-	return nil
-}
+func (SingleValue[N]) private() {}
 
 // HistogramValue summarizes a set of measurements as a histogram.
 type HistogramValue struct {
@@ -83,35 +58,4 @@ type HistogramValue struct {
 	Min, Max float64
 }
 
-func (v HistogramValue) fold(other value) error {
-	o, ok := other.(HistogramValue)
-	if !ok {
-		return fmt.Errorf("%w: value types %T and %T", errIncompatible, v, other)
-	}
-	if !sliceEqual[float64](v.Bounds, o.Bounds) || len(o.Counts) != len(v.Counts) {
-		return fmt.Errorf("%w: different histogram binning", errIncompatible)
-	}
-	v.Sum += o.Sum
-	for i, c := range o.Counts {
-		v.Counts[i] += c
-	}
-	if o.Min < v.Min {
-		v.Min = o.Min
-	}
-	if o.Max > v.Max {
-		v.Max = o.Max
-	}
-	return nil
-}
-
-func sliceEqual[T comparable](a, b []T) bool {
-	if len(a) != len(b) {
-		return false
-	}
-	for i, v := range a {
-		if v != b[i] {
-			return false
-		}
-	}
-	return true
-}
+func (HistogramValue) private() {}

From 0287a06a05ff39751ecfb916ad3b569f3d4be4f7 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 14:08:20 -0700
Subject: [PATCH 13/25] Rename Number to Atomic

---
 sdk/metric/internal/{number.go => atomic.go} | 15 ++++++++-------
 sdk/metric/internal/histogram.go             |  2 +-
 sdk/metric/internal/lastvalue.go             |  2 +-
 sdk/metric/internal/sum.go                   |  2 +-
 4 files changed, 11 insertions(+), 10 deletions(-)
 rename sdk/metric/internal/{number.go => atomic.go} (84%)

diff --git a/sdk/metric/internal/number.go b/sdk/metric/internal/atomic.go
similarity index 84%
rename from sdk/metric/internal/number.go
rename to sdk/metric/internal/atomic.go
index a6f4654b323..4a554974df5 100644
--- a/sdk/metric/internal/number.go
+++ b/sdk/metric/internal/atomic.go
@@ -22,7 +22,8 @@ import (
 	"sync/atomic"
 )
 
-type Number[N int64 | float64] interface {
+// Atomic provides atomic access to a generic value type.
+type Atomic[N int64 | float64] interface {
 	// Store value atomically.
 	Store(value N)
 
@@ -32,15 +33,15 @@ type Number[N int64 | float64] interface {
 	// Load returns the stored value.
 	Load() N
 
-	// Clone creates a new Number from the current value.
-	Clone() Number[N]
+	// Clone creates an independent copy of the current value.
+	Clone() Atomic[N]
 }
 
 type Int64 struct {
 	value *int64
 }
 
-var _ Number[int64] = Int64{}
+var _ Atomic[int64] = Int64{}
 
 func NewInt64(v int64) Int64 {
 	return Int64{value: &v}
@@ -49,7 +50,7 @@ func NewInt64(v int64) Int64 {
 func (v Int64) Store(value int64) { atomic.StoreInt64(v.value, value) }
 func (v Int64) Add(value int64)   { atomic.AddInt64(v.value, value) }
 func (v Int64) Load() int64       { return atomic.LoadInt64(v.value) }
-func (v Int64) Clone() Number[int64] {
+func (v Int64) Clone() Atomic[int64] {
 	return NewInt64(v.Load())
 }
 
@@ -57,7 +58,7 @@ type Float64 struct {
 	value *uint64
 }
 
-var _ Number[float64] = Float64{}
+var _ Atomic[float64] = Float64{}
 
 func NewFloat64(v float64) Float64 {
 	u := math.Float64bits(v)
@@ -82,6 +83,6 @@ func (v Float64) Load() float64 {
 	return math.Float64frombits(atomic.LoadUint64(v.value))
 }
 
-func (v Float64) Clone() Number[float64] {
+func (v Float64) Clone() Atomic[float64] {
 	return NewFloat64(v.Load())
 }
diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index 5c4fdd4c2e2..8bf73838b5d 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -31,7 +31,7 @@ type histogramAgg[N int64 | float64] struct {
 // NewHistogram returns an Aggregator that summarizes a set of measurements as
 // an histogram. The zero value will be used as the start value for all the
 // buckets of new Aggregations.
-func NewHistogram[N int64 | float64](zero Number[N], cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
+func NewHistogram[N int64 | float64](zero Atomic[N], cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
 	return &histogramAgg[N]{}
 }
 
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index 1e49456c368..74278d3679d 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -27,7 +27,7 @@ type lastValueAgg[N int64 | float64] struct {
 // NewLastValue returns an Aggregator that summarizes a set of measurements as
 // the last one made. The zero value will be used as the start value for all
 // new Aggregations.
-func NewLastValue[N int64 | float64](zero Number[N]) Aggregator[N] {
+func NewLastValue[N int64 | float64](zero Atomic[N]) Aggregator[N] {
 	return &lastValueAgg[N]{}
 }
 
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index 06702bd4c38..543c66390b0 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -27,7 +27,7 @@ type sumAgg[N int64 | float64] struct {
 // NewSum returns an Aggregator that summarizes a set of
 // measurements as their arithmetic sum. The zero value will be used as the
 // start value for all new Aggregations.
-func NewSum[N int64 | float64](zero Number[N]) Aggregator[N] {
+func NewSum[N int64 | float64](zero Atomic[N]) Aggregator[N] {
 	// TODO: implement.
 	return &sumAgg[N]{}
 }

From 36fad53be18efb3ed965ff67cae3a3ca9710d801 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 14:29:43 -0700
Subject: [PATCH 14/25] Add tests for Atomic impls

---
 sdk/metric/internal/atomic.go      |  6 +++
 sdk/metric/internal/atomic_test.go | 64 ++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 sdk/metric/internal/atomic_test.go

diff --git a/sdk/metric/internal/atomic.go b/sdk/metric/internal/atomic.go
index 4a554974df5..2ceeabf0f25 100644
--- a/sdk/metric/internal/atomic.go
+++ b/sdk/metric/internal/atomic.go
@@ -37,6 +37,9 @@ type Atomic[N int64 | float64] interface {
 	Clone() Atomic[N]
 }
 
+// Int64 is an int64 implementation of an Atomic.
+//
+// An Int64 must not be copied.
 type Int64 struct {
 	value *int64
 }
@@ -54,6 +57,9 @@ func (v Int64) Clone() Atomic[int64] {
 	return NewInt64(v.Load())
 }
 
+// Float64 is a float64 implementation of an Atomic.
+//
+// An Float64 must not be copied.
 type Float64 struct {
 	value *uint64
 }
diff --git a/sdk/metric/internal/atomic_test.go b/sdk/metric/internal/atomic_test.go
new file mode 100644
index 00000000000..67449e8c06f
--- /dev/null
+++ b/sdk/metric/internal/atomic_test.go
@@ -0,0 +1,64 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package internal
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+const routines = 5
+
+func testAtomic[N int64 | float64](t *testing.T, a Atomic[N]) {
+	n, clone := a.Load(), a.Clone()
+	require.Equal(t, n, clone.Load(), "Clone() did not copy value")
+
+	clone.Add(1)
+	assert.Equal(t, n, a.Load(), "Clone() returned original")
+	assert.Equal(t, n+1, clone.Load())
+
+	clone.Store(n)
+	assert.Equal(t, n, clone.Load())
+}
+
+func TestInt64(t *testing.T) {
+	var wg sync.WaitGroup
+	wg.Add(routines)
+	for i := int64(0); i < routines; i++ {
+		go func(n int64) {
+			defer wg.Done()
+			testAtomic[int64](t, NewInt64(n))
+		}(i)
+	}
+	wg.Wait()
+}
+
+func TestFloat64(t *testing.T) {
+	var wg sync.WaitGroup
+	wg.Add(routines)
+	for i := 0; i < routines; i++ {
+		go func(n float64) {
+			defer wg.Done()
+			testAtomic[float64](t, NewFloat64(n))
+		}(float64(i))
+	}
+	wg.Wait()
+}

From 47082f00bc67487c68743032b64223054868d758 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 14:31:25 -0700
Subject: [PATCH 15/25] Remove unneeded Atomic implementation

Add back when filling in structures.
---
 sdk/metric/internal/atomic.go      | 42 +-------------------
 sdk/metric/internal/atomic_test.go | 64 ------------------------------
 2 files changed, 1 insertion(+), 105 deletions(-)
 delete mode 100644 sdk/metric/internal/atomic_test.go

diff --git a/sdk/metric/internal/atomic.go b/sdk/metric/internal/atomic.go
index 2ceeabf0f25..e3b8bc7c938 100644
--- a/sdk/metric/internal/atomic.go
+++ b/sdk/metric/internal/atomic.go
@@ -19,22 +19,11 @@ package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import (
 	"math"
-	"sync/atomic"
 )
 
 // Atomic provides atomic access to a generic value type.
 type Atomic[N int64 | float64] interface {
-	// Store value atomically.
-	Store(value N)
-
-	// Add value atomically.
-	Add(value N)
-
-	// Load returns the stored value.
-	Load() N
-
-	// Clone creates an independent copy of the current value.
-	Clone() Atomic[N]
+	// TODO: Add needed atomic methods.
 }
 
 // Int64 is an int64 implementation of an Atomic.
@@ -50,13 +39,6 @@ func NewInt64(v int64) Int64 {
 	return Int64{value: &v}
 }
 
-func (v Int64) Store(value int64) { atomic.StoreInt64(v.value, value) }
-func (v Int64) Add(value int64)   { atomic.AddInt64(v.value, value) }
-func (v Int64) Load() int64       { return atomic.LoadInt64(v.value) }
-func (v Int64) Clone() Atomic[int64] {
-	return NewInt64(v.Load())
-}
-
 // Float64 is a float64 implementation of an Atomic.
 //
 // An Float64 must not be copied.
@@ -70,25 +52,3 @@ func NewFloat64(v float64) Float64 {
 	u := math.Float64bits(v)
 	return Float64{value: &u}
 }
-
-func (v Float64) Store(value float64) {
-	atomic.StoreUint64(v.value, math.Float64bits(value))
-}
-
-func (v Float64) Add(value float64) {
-	for {
-		old := atomic.LoadUint64(v.value)
-		sum := math.Float64bits(math.Float64frombits(old) + value)
-		if atomic.CompareAndSwapUint64(v.value, old, sum) {
-			return
-		}
-	}
-}
-
-func (v Float64) Load() float64 {
-	return math.Float64frombits(atomic.LoadUint64(v.value))
-}
-
-func (v Float64) Clone() Atomic[float64] {
-	return NewFloat64(v.Load())
-}
diff --git a/sdk/metric/internal/atomic_test.go b/sdk/metric/internal/atomic_test.go
deleted file mode 100644
index 67449e8c06f..00000000000
--- a/sdk/metric/internal/atomic_test.go
+++ /dev/null
@@ -1,64 +0,0 @@
-// Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build go1.18
-// +build go1.18
-
-package internal
-
-import (
-	"sync"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-)
-
-const routines = 5
-
-func testAtomic[N int64 | float64](t *testing.T, a Atomic[N]) {
-	n, clone := a.Load(), a.Clone()
-	require.Equal(t, n, clone.Load(), "Clone() did not copy value")
-
-	clone.Add(1)
-	assert.Equal(t, n, a.Load(), "Clone() returned original")
-	assert.Equal(t, n+1, clone.Load())
-
-	clone.Store(n)
-	assert.Equal(t, n, clone.Load())
-}
-
-func TestInt64(t *testing.T) {
-	var wg sync.WaitGroup
-	wg.Add(routines)
-	for i := int64(0); i < routines; i++ {
-		go func(n int64) {
-			defer wg.Done()
-			testAtomic[int64](t, NewInt64(n))
-		}(i)
-	}
-	wg.Wait()
-}
-
-func TestFloat64(t *testing.T) {
-	var wg sync.WaitGroup
-	wg.Add(routines)
-	for i := 0; i < routines; i++ {
-		go func(n float64) {
-			defer wg.Done()
-			testAtomic[float64](t, NewFloat64(n))
-		}(float64(i))
-	}
-	wg.Wait()
-}

From 86061ccca45a105d44cafa500f89340835bdf74d Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 14:32:47 -0700
Subject: [PATCH 16/25] Fix article in Float64 docs

---
 sdk/metric/internal/atomic.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/metric/internal/atomic.go b/sdk/metric/internal/atomic.go
index e3b8bc7c938..9f004fdd921 100644
--- a/sdk/metric/internal/atomic.go
+++ b/sdk/metric/internal/atomic.go
@@ -41,7 +41,7 @@ func NewInt64(v int64) Int64 {
 
 // Float64 is a float64 implementation of an Atomic.
 //
-// An Float64 must not be copied.
+// A Float64 must not be copied.
 type Float64 struct {
 	value *uint64
 }

From fc0f30efa3da1c394ab3c9b4c8b8a01a146a6ad3 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 15:41:25 -0700
Subject: [PATCH 17/25] Remove Atomic

This is an implementation detail.
---
 sdk/metric/internal/atomic.go    | 54 --------------------------------
 sdk/metric/internal/histogram.go |  2 +-
 sdk/metric/internal/lastvalue.go |  2 +-
 sdk/metric/internal/sum.go       |  2 +-
 4 files changed, 3 insertions(+), 57 deletions(-)
 delete mode 100644 sdk/metric/internal/atomic.go

diff --git a/sdk/metric/internal/atomic.go b/sdk/metric/internal/atomic.go
deleted file mode 100644
index 9f004fdd921..00000000000
--- a/sdk/metric/internal/atomic.go
+++ /dev/null
@@ -1,54 +0,0 @@
-// Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build go1.18
-// +build go1.18
-
-package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
-
-import (
-	"math"
-)
-
-// Atomic provides atomic access to a generic value type.
-type Atomic[N int64 | float64] interface {
-	// TODO: Add needed atomic methods.
-}
-
-// Int64 is an int64 implementation of an Atomic.
-//
-// An Int64 must not be copied.
-type Int64 struct {
-	value *int64
-}
-
-var _ Atomic[int64] = Int64{}
-
-func NewInt64(v int64) Int64 {
-	return Int64{value: &v}
-}
-
-// Float64 is a float64 implementation of an Atomic.
-//
-// A Float64 must not be copied.
-type Float64 struct {
-	value *uint64
-}
-
-var _ Atomic[float64] = Float64{}
-
-func NewFloat64(v float64) Float64 {
-	u := math.Float64bits(v)
-	return Float64{value: &u}
-}
diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index 8bf73838b5d..5338550f429 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -31,7 +31,7 @@ type histogramAgg[N int64 | float64] struct {
 // NewHistogram returns an Aggregator that summarizes a set of measurements as
 // an histogram. The zero value will be used as the start value for all the
 // buckets of new Aggregations.
-func NewHistogram[N int64 | float64](zero Atomic[N], cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
+func NewHistogram[N int64 | float64](cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
 	return &histogramAgg[N]{}
 }
 
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index 74278d3679d..93ad99d6edb 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -27,7 +27,7 @@ type lastValueAgg[N int64 | float64] struct {
 // NewLastValue returns an Aggregator that summarizes a set of measurements as
 // the last one made. The zero value will be used as the start value for all
 // new Aggregations.
-func NewLastValue[N int64 | float64](zero Atomic[N]) Aggregator[N] {
+func NewLastValue[N int64 | float64]() Aggregator[N] {
 	return &lastValueAgg[N]{}
 }
 
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index 543c66390b0..7ad46459df9 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -27,7 +27,7 @@ type sumAgg[N int64 | float64] struct {
 // NewSum returns an Aggregator that summarizes a set of
 // measurements as their arithmetic sum. The zero value will be used as the
 // start value for all new Aggregations.
-func NewSum[N int64 | float64](zero Atomic[N]) Aggregator[N] {
+func NewSum[N int64 | float64]() Aggregator[N] {
 	// TODO: implement.
 	return &sumAgg[N]{}
 }

From 658f4a5a6596ce1c65d19578eb5e7f0a89e9c395 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Tue, 21 Jun 2022 19:30:26 -0700
Subject: [PATCH 18/25] Add aggregator_example_test

---
 .../internal/aggregator_example_test.go       | 126 ++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 sdk/metric/internal/aggregator_example_test.go

diff --git a/sdk/metric/internal/aggregator_example_test.go b/sdk/metric/internal/aggregator_example_test.go
new file mode 100644
index 00000000000..9b61be9a9d6
--- /dev/null
+++ b/sdk/metric/internal/aggregator_example_test.go
@@ -0,0 +1,126 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.18
+// +build go1.18
+
+package internal
+
+import (
+	"context"
+	"fmt"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric/instrument"
+	"go.opentelemetry.io/otel/metric/instrument/syncint64"
+	"go.opentelemetry.io/otel/sdk/metric/aggregation"
+)
+
+type meter struct {
+	// When a reader initiates a collection, the meter would collect
+	// aggregations from each of these cyclers. In this process they will
+	// progress the aggregation period of each instrument's aggregator.
+	cyclers []Cycler
+}
+
+func (m *meter) SyncInt64() syncint64.InstrumentProvider {
+	// The same would be done for all the other instrument providers.
+	return (*syncInt64Provider)(m)
+}
+
+type syncInt64Provider meter
+
+func (p *syncInt64Provider) Counter(string, ...instrument.Option) (syncint64.Counter, error) {
+	// This is an example of how a synchronous int64 provider would create an
+	// aggregator and cycler for a new counter. At this point the provider
+	// would determine the aggregation and temporality to used based on the
+	// Reader and View configuration. Assume here these are determined to be a
+	// cumulative sum.
+
+	aggregator := NewSum[int64]()
+	count := inst{agg: aggregator}
+
+	cycler := NewCumulativeCylcer(aggregator)
+	p.cyclers = append(p.cyclers, cycler)
+
+	return count, nil
+}
+
+func (p *syncInt64Provider) UpDownCounter(string, ...instrument.Option) (syncint64.UpDownCounter, error) {
+	// This is an example of how a synchronous int64 provider would create an
+	// aggregator and cycler for a new up-down counter. At this point the
+	// provider would determine the aggregation and temporality to used based
+	// on the Reader and View configuration. Assume here these are determined
+	// to be a delta last-value.
+
+	aggregator := NewLastValue[int64]()
+	upDownCount := inst{agg: aggregator}
+
+	cycler := NewDeltaCylcer(aggregator)
+	p.cyclers = append(p.cyclers, cycler)
+
+	return upDownCount, nil
+}
+
+func (p *syncInt64Provider) Histogram(string, ...instrument.Option) (syncint64.Histogram, error) {
+	// This is an example of how a synchronous int64 provider would create an
+	// aggregator and cycler for a new histogram. At this point the provider
+	// would determine the aggregation and temporality to used based on the
+	// Reader and View configuration. Assume here these are determined to be a
+	// delta explicit-bucket histogram.
+
+	aggregator := NewHistogram[int64](aggregation.ExplicitBucketHistogram{
+		Boundaries: []float64{0, 5, 10, 25, 50, 75, 100, 250, 500, 1000},
+		NoMinMax:   false,
+	})
+	hist := inst{agg: aggregator}
+
+	cycler := NewDeltaCylcer(aggregator)
+	p.cyclers = append(p.cyclers, cycler)
+
+	return hist, nil
+}
+
+// inst is a generalized int64 synchronous counter, up-down counter, and
+// histogram used for demonstration purposes only.
+type inst struct {
+	instrument.Synchronous
+
+	agg Aggregator[int64]
+}
+
+func (inst) Add(context.Context, int64, ...attribute.KeyValue)    {}
+func (inst) Record(context.Context, int64, ...attribute.KeyValue) {}
+
+func Example() {
+	m := meter{}
+	provider := m.SyncInt64()
+
+	count, _ := provider.Counter("counter example")
+	fmt.Printf("counter aggregator: %T\n", count.(inst).agg)
+
+	upDownCount, _ := provider.UpDownCounter("up-down counter example")
+	fmt.Printf("up-down counter aggregator: %T\n", upDownCount.(inst).agg)
+
+	hist, _ := provider.UpDownCounter("histogram example")
+	fmt.Printf("histogram aggregator: %T\n", hist.(inst).agg)
+
+	fmt.Printf("meter cyclers: %T{%T, %T, %T}\n", m.cyclers, m.cyclers[0], m.cyclers[1], m.cyclers[2])
+
+	// Output:
+	// counter aggregator: *internal.sumAgg[int64]
+	// up-down counter aggregator: *internal.lastValueAgg[int64]
+	// histogram aggregator: *internal.lastValueAgg[int64]
+	// meter cyclers: []internal.Cycler{internal.cumulativeCylcer[int64], internal.deltaCylcer[int64], internal.deltaCylcer[int64]}
+}

From 02488a235352aa110e4eb01c2f093a5373c9ec1d Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Wed, 22 Jun 2022 08:19:45 -0700
Subject: [PATCH 19/25] Fix hist example

---
 sdk/metric/internal/aggregator_example_test.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sdk/metric/internal/aggregator_example_test.go b/sdk/metric/internal/aggregator_example_test.go
index 9b61be9a9d6..6b76092919c 100644
--- a/sdk/metric/internal/aggregator_example_test.go
+++ b/sdk/metric/internal/aggregator_example_test.go
@@ -113,7 +113,7 @@ func Example() {
 	upDownCount, _ := provider.UpDownCounter("up-down counter example")
 	fmt.Printf("up-down counter aggregator: %T\n", upDownCount.(inst).agg)
 
-	hist, _ := provider.UpDownCounter("histogram example")
+	hist, _ := provider.Histogram("histogram example")
 	fmt.Printf("histogram aggregator: %T\n", hist.(inst).agg)
 
 	fmt.Printf("meter cyclers: %T{%T, %T, %T}\n", m.cyclers, m.cyclers[0], m.cyclers[1], m.cyclers[2])
@@ -121,6 +121,6 @@ func Example() {
 	// Output:
 	// counter aggregator: *internal.sumAgg[int64]
 	// up-down counter aggregator: *internal.lastValueAgg[int64]
-	// histogram aggregator: *internal.lastValueAgg[int64]
+	// histogram aggregator: *internal.histogramAgg[int64]
 	// meter cyclers: []internal.Cycler{internal.cumulativeCylcer[int64], internal.deltaCylcer[int64], internal.deltaCylcer[int64]}
 }

From c266e46cf6c55d17961fa05aadbde2dd36a56150 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Wed, 22 Jun 2022 08:41:47 -0700
Subject: [PATCH 20/25] Add issue numbers to all TODO and FIXME

---
 sdk/metric/internal/aggregation.go |  4 ++--
 sdk/metric/internal/cycler.go      | 12 ++++++------
 sdk/metric/internal/histogram.go   |  8 ++++----
 sdk/metric/internal/lastvalue.go   |  8 ++++----
 sdk/metric/internal/sum.go         | 10 +++++-----
 5 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/sdk/metric/internal/aggregation.go b/sdk/metric/internal/aggregation.go
index 71ad88cbca3..4149f2672cb 100644
--- a/sdk/metric/internal/aggregation.go
+++ b/sdk/metric/internal/aggregation.go
@@ -24,8 +24,8 @@ import (
 // Aggregation is a single data point in a timeseries that summarizes
 // measurements made during a time span.
 type Aggregation struct {
-	// TODO: Replace this with the export.Aggregation type once #2961 is
-	// merged.
+	// TODO(#2968): Replace this with the export.Aggregation type once #2961
+	// is merged.
 
 	// Timestamp defines the time the last measurement was made. If zero, no
 	// measurements were made for this time span. The time is represented as a
diff --git a/sdk/metric/internal/cycler.go b/sdk/metric/internal/cycler.go
index d8bbaeae9cd..e37a855b24c 100644
--- a/sdk/metric/internal/cycler.go
+++ b/sdk/metric/internal/cycler.go
@@ -25,8 +25,8 @@ type Cycler interface {
 	// returned reflects this.
 	Cycle() []Aggregation
 
-	// TODO: Replace the return type with []export.Aggregation once #2961 is
-	// merged.
+	// TODO(#2968): Replace the return type with []export.Aggregation once
+	// #2961 is merged.
 }
 
 // deltaCylcer cycles aggregation periods by returning the aggregation
@@ -47,22 +47,22 @@ func (c deltaCylcer[N]) Cycle() []Aggregation {
 // cumulativeCylcer cycles aggregation periods by returning the cumulative
 // aggregation from its start time until the current period.
 type cumulativeCylcer[N int64 | float64] struct {
-	// TODO: implement a cumulative storing field.
+	// TODO(#2969): implement a cumulative storing field.
 	aggregator Aggregator[N]
 }
 
 func NewCumulativeCylcer[N int64 | float64](a Aggregator[N]) Cycler {
 	c := cumulativeCylcer[N]{aggregator: a}
 
-	// TODO: Initialize a new cumulative storage.
+	// TODO(#2969): Initialize a new cumulative storage.
 
 	return c
 }
 
 func (c cumulativeCylcer[N]) Cycle() []Aggregation {
-	// TODO: Update cumulative storage of aggregations and return them.
+	// TODO(#2969): Update cumulative storage of aggregations and return them.
 
-	// FIXME: currently this returns a delta representation of the
+	// FIXME(#2969): currently this returns a delta representation of the
 	// aggregation. When the cumulative storage is complete it should return a
 	// cumulative representation.
 	return c.aggregator.flush()
diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index 5338550f429..5b0dea85fc3 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -25,7 +25,7 @@ import (
 // histogramAgg summarizes a set of measurements as an histogram with
 // explicitly defined buckets.
 type histogramAgg[N int64 | float64] struct {
-	// TODO: implement.
+	// TODO(#2970): implement.
 }
 
 // NewHistogram returns an Aggregator that summarizes a set of measurements as
@@ -36,14 +36,14 @@ func NewHistogram[N int64 | float64](cfg aggregation.ExplicitBucketHistogram) Ag
 }
 
 func (s *histogramAgg[N]) Aggregate(value N, attr *attribute.Set) {
-	// TODO: implement.
+	// TODO(#2970): implement.
 }
 
 func (s *histogramAgg[N]) flush() []Aggregation {
-	// TODO: implement.
+	// TODO(#2970): implement.
 	return []Aggregation{
 		{
-			Value: HistogramValue{ /* TODO: calculate. */ },
+			Value: HistogramValue{ /* TODO(#2970): calculate. */ },
 		},
 	}
 }
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index 93ad99d6edb..2756cfbef9f 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -21,7 +21,7 @@ import "go.opentelemetry.io/otel/attribute"
 
 // lastValueAgg summarizes a set of measurements as the last one made.
 type lastValueAgg[N int64 | float64] struct {
-	// TODO: implement.
+	// TODO(#2971): implement.
 }
 
 // NewLastValue returns an Aggregator that summarizes a set of measurements as
@@ -32,14 +32,14 @@ func NewLastValue[N int64 | float64]() Aggregator[N] {
 }
 
 func (s *lastValueAgg[N]) Aggregate(value N, attr *attribute.Set) {
-	// TODO: implement.
+	// TODO(#2971): implement.
 }
 
 func (s *lastValueAgg[N]) flush() []Aggregation {
-	// TODO: implement.
+	// TODO(#2971): implement.
 	return []Aggregation{
 		{
-			Value: SingleValue[N]{ /* TODO: calculate */ },
+			Value: SingleValue[N]{ /* TODO(#2971): calculate */ },
 		},
 	}
 }
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index 7ad46459df9..7210e10a6a8 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -21,26 +21,26 @@ import "go.opentelemetry.io/otel/attribute"
 
 // sumAgg summarizes a set of measurements as their arithmetic sum.
 type sumAgg[N int64 | float64] struct {
-	// TODO: implement.
+	// TODO(#2972): implement.
 }
 
 // NewSum returns an Aggregator that summarizes a set of
 // measurements as their arithmetic sum. The zero value will be used as the
 // start value for all new Aggregations.
 func NewSum[N int64 | float64]() Aggregator[N] {
-	// TODO: implement.
+	// TODO(#2972): implement.
 	return &sumAgg[N]{}
 }
 
 func (s *sumAgg[N]) Aggregate(value N, attr *attribute.Set) {
-	// TODO: implement.
+	// TODO(#2972): implement.
 }
 
 func (s *sumAgg[N]) flush() []Aggregation {
-	// TODO: implement.
+	// TODO(#2972): implement.
 	return []Aggregation{
 		{
-			Value: SingleValue[N]{ /* TODO: calculate */ },
+			Value: SingleValue[N]{ /* TODO(#2972): calculate */ },
 		},
 	}
 }

From 3057ac24ac39ceff849c28531407321c0d3fcbb8 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Wed, 22 Jun 2022 09:31:08 -0700
Subject: [PATCH 21/25] Remove zero parameter comment

---
 sdk/metric/internal/histogram.go | 3 +--
 sdk/metric/internal/lastvalue.go | 3 +--
 sdk/metric/internal/sum.go       | 3 +--
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index 5b0dea85fc3..90d442c8d84 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -29,8 +29,7 @@ type histogramAgg[N int64 | float64] struct {
 }
 
 // NewHistogram returns an Aggregator that summarizes a set of measurements as
-// an histogram. The zero value will be used as the start value for all the
-// buckets of new Aggregations.
+// an histogram.
 func NewHistogram[N int64 | float64](cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
 	return &histogramAgg[N]{}
 }
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index 2756cfbef9f..467eeae4c18 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -25,8 +25,7 @@ type lastValueAgg[N int64 | float64] struct {
 }
 
 // NewLastValue returns an Aggregator that summarizes a set of measurements as
-// the last one made. The zero value will be used as the start value for all
-// new Aggregations.
+// the last one made.
 func NewLastValue[N int64 | float64]() Aggregator[N] {
 	return &lastValueAgg[N]{}
 }
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index 7210e10a6a8..0fb0eebfeb4 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -25,8 +25,7 @@ type sumAgg[N int64 | float64] struct {
 }
 
 // NewSum returns an Aggregator that summarizes a set of
-// measurements as their arithmetic sum. The zero value will be used as the
-// start value for all new Aggregations.
+// measurements as their arithmetic sum.
 func NewSum[N int64 | float64]() Aggregator[N] {
 	// TODO(#2972): implement.
 	return &sumAgg[N]{}

From 6b39c546587550b435a923e2ff4b0d513b8f7fab Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Thu, 23 Jun 2022 14:06:37 -0700
Subject: [PATCH 22/25] Combine the cycler into the aggregators

---
 sdk/metric/internal/aggregator.go             | 12 +--
 .../internal/aggregator_example_test.go       | 74 +++++++++----------
 sdk/metric/internal/cycler.go                 | 69 -----------------
 sdk/metric/internal/drop.go                   |  2 +-
 sdk/metric/internal/histogram.go              | 58 +++++++++++----
 sdk/metric/internal/lastvalue.go              | 16 ++--
 sdk/metric/internal/sum.go                    | 58 +++++++++++----
 7 files changed, 135 insertions(+), 154 deletions(-)
 delete mode 100644 sdk/metric/internal/cycler.go

diff --git a/sdk/metric/internal/aggregator.go b/sdk/metric/internal/aggregator.go
index 2f2b11dc83a..63489f1ae8b 100644
--- a/sdk/metric/internal/aggregator.go
+++ b/sdk/metric/internal/aggregator.go
@@ -20,18 +20,12 @@ package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 import "go.opentelemetry.io/otel/attribute"
 
 // Aggregator forms an aggregation from a collection of recorded measurements.
-// Aggregators are use with Cyclers to collect and produce metrics from
-// instrument measurements. Aggregators handle the collection (and
-// aggregation) of measurements, while Cyclers handle how those aggregated
-// measurements are combined and then produced to the telemetry pipeline.
 type Aggregator[N int64 | float64] interface {
 	// Aggregate records the measurement, scoped by attr, and aggregates it
 	// into an aggregation.
 	Aggregate(measurement N, attr *attribute.Set)
 
-	// flush clears aggregations that have been recorded. The Aggregator
-	// resets itself for a new aggregation period when called, it does not
-	// carry forward any state. If aggregation periods need to be combined it
-	// is the callers responsibility to achieve this.
-	flush() []Aggregation
+	// Aggregations retuns a slice of Aggregation, one per each attribute set
+	// used to scope measurement aggregation, and ends an aggregation cycle.
+	Aggregations() []Aggregation
 }
diff --git a/sdk/metric/internal/aggregator_example_test.go b/sdk/metric/internal/aggregator_example_test.go
index 6b76092919c..04db712016a 100644
--- a/sdk/metric/internal/aggregator_example_test.go
+++ b/sdk/metric/internal/aggregator_example_test.go
@@ -29,9 +29,9 @@ import (
 
 type meter struct {
 	// When a reader initiates a collection, the meter would collect
-	// aggregations from each of these cyclers. In this process they will
+	// aggregations from each of these functions. In this process they will
 	// progress the aggregation period of each instrument's aggregator.
-	cyclers []Cycler
+	aggregationFuncs []func() []Aggregation
 }
 
 func (m *meter) SyncInt64() syncint64.InstrumentProvider {
@@ -43,51 +43,55 @@ type syncInt64Provider meter
 
 func (p *syncInt64Provider) Counter(string, ...instrument.Option) (syncint64.Counter, error) {
 	// This is an example of how a synchronous int64 provider would create an
-	// aggregator and cycler for a new counter. At this point the provider
-	// would determine the aggregation and temporality to used based on the
-	// Reader and View configuration. Assume here these are determined to be a
+	// aggregator for a new counter. At this point the provider would
+	// determine the aggregation and temporality to used based on the Reader
+	// and View configuration. Assume here these are determined to be a
 	// cumulative sum.
 
-	aggregator := NewSum[int64]()
-	count := inst{agg: aggregator}
+	aggregator := NewCumulativeSum[int64]()
+	count := inst{aggregateFunc: aggregator.Aggregate}
 
-	cycler := NewCumulativeCylcer(aggregator)
-	p.cyclers = append(p.cyclers, cycler)
+	p.aggregationFuncs = append(p.aggregationFuncs, aggregator.Aggregations)
+
+	fmt.Printf("using %T aggregator for counter\n", aggregator)
 
 	return count, nil
 }
 
 func (p *syncInt64Provider) UpDownCounter(string, ...instrument.Option) (syncint64.UpDownCounter, error) {
 	// This is an example of how a synchronous int64 provider would create an
-	// aggregator and cycler for a new up-down counter. At this point the
-	// provider would determine the aggregation and temporality to used based
-	// on the Reader and View configuration. Assume here these are determined
-	// to be a delta last-value.
+	// aggregator for a new up-down counter. At this point the provider would
+	// determine the aggregation and temporality to used based on the Reader
+	// and View configuration. Assume here these are determined to be a
+	// last-value aggregation (the temporality does not affect the produced
+	// aggregations).
 
 	aggregator := NewLastValue[int64]()
-	upDownCount := inst{agg: aggregator}
+	upDownCount := inst{aggregateFunc: aggregator.Aggregate}
+
+	p.aggregationFuncs = append(p.aggregationFuncs, aggregator.Aggregations)
 
-	cycler := NewDeltaCylcer(aggregator)
-	p.cyclers = append(p.cyclers, cycler)
+	fmt.Printf("using %T aggregator for up-down counter\n", aggregator)
 
 	return upDownCount, nil
 }
 
 func (p *syncInt64Provider) Histogram(string, ...instrument.Option) (syncint64.Histogram, error) {
 	// This is an example of how a synchronous int64 provider would create an
-	// aggregator and cycler for a new histogram. At this point the provider
-	// would determine the aggregation and temporality to used based on the
-	// Reader and View configuration. Assume here these are determined to be a
-	// delta explicit-bucket histogram.
+	// aggregator for a new histogram. At this point the provider would
+	// determine the aggregation and temporality to used based on the Reader
+	// and View configuration. Assume here these are determined to be a delta
+	// explicit-bucket histogram.
 
-	aggregator := NewHistogram[int64](aggregation.ExplicitBucketHistogram{
+	aggregator := NewDeltaHistogram[int64](aggregation.ExplicitBucketHistogram{
 		Boundaries: []float64{0, 5, 10, 25, 50, 75, 100, 250, 500, 1000},
 		NoMinMax:   false,
 	})
-	hist := inst{agg: aggregator}
+	hist := inst{aggregateFunc: aggregator.Aggregate}
+
+	p.aggregationFuncs = append(p.aggregationFuncs, aggregator.Aggregations)
 
-	cycler := NewDeltaCylcer(aggregator)
-	p.cyclers = append(p.cyclers, cycler)
+	fmt.Printf("using %T aggregator for histogram\n", aggregator)
 
 	return hist, nil
 }
@@ -97,7 +101,7 @@ func (p *syncInt64Provider) Histogram(string, ...instrument.Option) (syncint64.H
 type inst struct {
 	instrument.Synchronous
 
-	agg Aggregator[int64]
+	aggregateFunc func(int64, *attribute.Set)
 }
 
 func (inst) Add(context.Context, int64, ...attribute.KeyValue)    {}
@@ -107,20 +111,12 @@ func Example() {
 	m := meter{}
 	provider := m.SyncInt64()
 
-	count, _ := provider.Counter("counter example")
-	fmt.Printf("counter aggregator: %T\n", count.(inst).agg)
-
-	upDownCount, _ := provider.UpDownCounter("up-down counter example")
-	fmt.Printf("up-down counter aggregator: %T\n", upDownCount.(inst).agg)
-
-	hist, _ := provider.Histogram("histogram example")
-	fmt.Printf("histogram aggregator: %T\n", hist.(inst).agg)
-
-	fmt.Printf("meter cyclers: %T{%T, %T, %T}\n", m.cyclers, m.cyclers[0], m.cyclers[1], m.cyclers[2])
+	provider.Counter("counter example")
+	provider.UpDownCounter("up-down counter example")
+	provider.Histogram("histogram example")
 
 	// Output:
-	// counter aggregator: *internal.sumAgg[int64]
-	// up-down counter aggregator: *internal.lastValueAgg[int64]
-	// histogram aggregator: *internal.histogramAgg[int64]
-	// meter cyclers: []internal.Cycler{internal.cumulativeCylcer[int64], internal.deltaCylcer[int64], internal.deltaCylcer[int64]}
+	// using *internal.cumulativeSum[int64] aggregator for counter
+	// using *internal.lastValue[int64] aggregator for up-down counter
+	// using *internal.deltaHistogram[int64] aggregator for histogram
 }
diff --git a/sdk/metric/internal/cycler.go b/sdk/metric/internal/cycler.go
deleted file mode 100644
index e37a855b24c..00000000000
--- a/sdk/metric/internal/cycler.go
+++ /dev/null
@@ -1,69 +0,0 @@
-// Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build go1.18
-// +build go1.18
-
-package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
-
-// Cycler cycles aggregation periods. It will handle any state progression
-// from one period to the next based on the temporality of the cycling.
-type Cycler interface {
-	// Cycle returns an []Aggregation for the current period. If the cycler
-	// merges state from previous periods into the current, the []Aggregation
-	// returned reflects this.
-	Cycle() []Aggregation
-
-	// TODO(#2968): Replace the return type with []export.Aggregation once
-	// #2961 is merged.
-}
-
-// deltaCylcer cycles aggregation periods by returning the aggregation
-// produces from that period only. No state is maintained from one period to
-// the next.
-type deltaCylcer[N int64 | float64] struct {
-	aggregator Aggregator[N]
-}
-
-func NewDeltaCylcer[N int64 | float64](a Aggregator[N]) Cycler {
-	return deltaCylcer[N]{aggregator: a}
-}
-
-func (c deltaCylcer[N]) Cycle() []Aggregation {
-	return c.aggregator.flush()
-}
-
-// cumulativeCylcer cycles aggregation periods by returning the cumulative
-// aggregation from its start time until the current period.
-type cumulativeCylcer[N int64 | float64] struct {
-	// TODO(#2969): implement a cumulative storing field.
-	aggregator Aggregator[N]
-}
-
-func NewCumulativeCylcer[N int64 | float64](a Aggregator[N]) Cycler {
-	c := cumulativeCylcer[N]{aggregator: a}
-
-	// TODO(#2969): Initialize a new cumulative storage.
-
-	return c
-}
-
-func (c cumulativeCylcer[N]) Cycle() []Aggregation {
-	// TODO(#2969): Update cumulative storage of aggregations and return them.
-
-	// FIXME(#2969): currently this returns a delta representation of the
-	// aggregation. When the cumulative storage is complete it should return a
-	// cumulative representation.
-	return c.aggregator.flush()
-}
diff --git a/sdk/metric/internal/drop.go b/sdk/metric/internal/drop.go
index 23d32676fba..8a52910ae6f 100644
--- a/sdk/metric/internal/drop.go
+++ b/sdk/metric/internal/drop.go
@@ -28,4 +28,4 @@ func NewDrop[N int64 | float64]() Aggregator[N] { return &dropAgg[N]{} }
 
 func (s *dropAgg[N]) Aggregate(N, *attribute.Set) {}
 
-func (s *dropAgg[N]) flush() []Aggregation { return nil }
+func (s *dropAgg[N]) Aggregations() []Aggregation { return nil }
diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index 90d442c8d84..f25e9aa7430 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -22,27 +22,59 @@ import (
 	"go.opentelemetry.io/otel/sdk/metric/aggregation"
 )
 
-// histogramAgg summarizes a set of measurements as an histogram with
+// histogram summarizes a set of measurements as an histogram with
 // explicitly defined buckets.
-type histogramAgg[N int64 | float64] struct {
+type histogram[N int64 | float64] struct {
 	// TODO(#2970): implement.
 }
 
-// NewHistogram returns an Aggregator that summarizes a set of measurements as
-// an histogram.
-func NewHistogram[N int64 | float64](cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
-	return &histogramAgg[N]{}
+func (s *histogram[N]) Aggregate(value N, attr *attribute.Set) {
+	// TODO(#2970): implement.
+}
+
+// NewDeltaHistogram returns an Aggregator that summarizes a set of
+// measurements as an histogram. Each histogram is scoped by attributes and
+// the aggregation cycle the measurements were made in.
+//
+// Each aggregation cycle is treated independently. When the returned
+// Aggregator's Aggregations method is called it will reset all histogram
+// counts to zero.
+func NewDeltaHistogram[N int64 | float64](cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
+	return &deltaHistogram[N]{}
+}
+
+// deltaHistogram summarizes a set of measurements made in a single
+// aggregation cycle as an histogram with explicitly defined buckets.
+type deltaHistogram[N int64 | float64] struct {
+	histogram[N]
+
+	// TODO(#2970): implement.
 }
 
-func (s *histogramAgg[N]) Aggregate(value N, attr *attribute.Set) {
+func (s *deltaHistogram[N]) Aggregations() []Aggregation {
+	// TODO(#2970): implement.
+	return nil
+}
+
+// NewCumulativeHistogram returns an Aggregator that summarizes a set of
+// measurements as an histogram. Each histogram is scoped by attributes.
+//
+// Each aggregation cycle builds from the previous, the histogram counts are
+// the bucketed counts of all values aggregated since the returned Aggregator
+// was created.
+func NewCumulativeHistogram[N int64 | float64](cfg aggregation.ExplicitBucketHistogram) Aggregator[N] {
+	return &cumulativeHistogram[N]{}
+}
+
+// cumulativeHistogram summarizes a set of measurements made over all
+// aggregation cycles as an histogram with explicitly defined buckets.
+type cumulativeHistogram[N int64 | float64] struct {
+	histogram[N]
+
 	// TODO(#2970): implement.
 }
 
-func (s *histogramAgg[N]) flush() []Aggregation {
+func (s *cumulativeHistogram[N]) Aggregations() []Aggregation {
 	// TODO(#2970): implement.
-	return []Aggregation{
-		{
-			Value: HistogramValue{ /* TODO(#2970): calculate. */ },
-		},
-	}
+	return nil
 }
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index 467eeae4c18..b4e5fa51590 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -19,26 +19,22 @@ package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import "go.opentelemetry.io/otel/attribute"
 
-// lastValueAgg summarizes a set of measurements as the last one made.
-type lastValueAgg[N int64 | float64] struct {
+// lastValue summarizes a set of measurements as the last one made.
+type lastValue[N int64 | float64] struct {
 	// TODO(#2971): implement.
 }
 
 // NewLastValue returns an Aggregator that summarizes a set of measurements as
 // the last one made.
 func NewLastValue[N int64 | float64]() Aggregator[N] {
-	return &lastValueAgg[N]{}
+	return &lastValue[N]{}
 }
 
-func (s *lastValueAgg[N]) Aggregate(value N, attr *attribute.Set) {
+func (s *lastValue[N]) Aggregate(value N, attr *attribute.Set) {
 	// TODO(#2971): implement.
 }
 
-func (s *lastValueAgg[N]) flush() []Aggregation {
+func (s *lastValue[N]) Aggregations() []Aggregation {
 	// TODO(#2971): implement.
-	return []Aggregation{
-		{
-			Value: SingleValue[N]{ /* TODO(#2971): calculate */ },
-		},
-	}
+	return nil
 }
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index 0fb0eebfeb4..6315bf70d44 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -19,27 +19,59 @@ package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
 
 import "go.opentelemetry.io/otel/attribute"
 
-// sumAgg summarizes a set of measurements as their arithmetic sum.
-type sumAgg[N int64 | float64] struct {
+// sum summarizes a set of measurements as their arithmetic sum.
+type sum[N int64 | float64] struct {
 	// TODO(#2972): implement.
 }
 
-// NewSum returns an Aggregator that summarizes a set of
-// measurements as their arithmetic sum.
-func NewSum[N int64 | float64]() Aggregator[N] {
+func (s *sum[N]) Aggregate(value N, attr *attribute.Set) {
 	// TODO(#2972): implement.
-	return &sumAgg[N]{}
 }
 
-func (s *sumAgg[N]) Aggregate(value N, attr *attribute.Set) {
+// NewDeltaSum returns an Aggregator that summarizes a set of measurements as
+// their arithmetic sum. Each sum is scoped by attributes and the aggregation
+// cycle the measurements were made in.
+//
+// Each aggregation cycle is treated independently. When the returned
+// Aggregator's Aggregations method is called it will reset all sums to zero.
+func NewDeltaSum[N int64 | float64]() Aggregator[N] {
+	// TODO(#2972): implement.
+	return &deltaSum[N]{}
+}
+
+// deltaSum summarizes a set of measurements made in a single aggregation
+// cycle as their arithmetic sum.
+type deltaSum[N int64 | float64] struct {
+	sum[N]
+
+	// TODO(#2972): implement.
+}
+
+func (s *deltaSum[N]) Aggregations() []Aggregation {
+	// TODO(#2972): implement.
+	return nil
+}
+
+// NewCumulativeSum returns an Aggregator that summarizes a set of
+// measurements as their arithmetic sum. Each sum is scoped by attributes.
+//
+// Each aggregation cycle builds from the previous, the sums are the
+// arithmetic sum of all values aggregated since the returned Aggregator was
+// created.
+func NewCumulativeSum[N int64 | float64]() Aggregator[N] {
+	// TODO(#2972): implement.
+	return &cumulativeSum[N]{}
+}
+
+// cumulativeSum summarizes a set of measurements made over all aggregation
+// cycles as their arithmetic sum.
+type cumulativeSum[N int64 | float64] struct {
+	sum[N]
+
 	// TODO(#2972): implement.
 }
 
-func (s *sumAgg[N]) flush() []Aggregation {
+func (s *cumulativeSum[N]) Aggregations() []Aggregation {
 	// TODO(#2972): implement.
-	return []Aggregation{
-		{
-			Value: SingleValue[N]{ /* TODO(#2972): calculate */ },
-		},
-	}
+	return nil
 }

From 02edebdab0549422c259c31de4019558b00916e5 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Thu, 23 Jun 2022 14:07:10 -0700
Subject: [PATCH 23/25] Remove the drop aggregator

---
 sdk/metric/internal/drop.go | 31 -------------------------------
 1 file changed, 31 deletions(-)
 delete mode 100644 sdk/metric/internal/drop.go

diff --git a/sdk/metric/internal/drop.go b/sdk/metric/internal/drop.go
deleted file mode 100644
index 8a52910ae6f..00000000000
--- a/sdk/metric/internal/drop.go
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build go1.18
-// +build go1.18
-
-package internal // import "go.opentelemetry.io/otel/sdk/metric/internal"
-
-import "go.opentelemetry.io/otel/attribute"
-
-// dropAgg drops all recorded data and returns an empty Aggregation.
-type dropAgg[N int64 | float64] struct{}
-
-// NewDrop returns an Aggregator that drops all recorded data and returns an
-// empty Aggregation.
-func NewDrop[N int64 | float64]() Aggregator[N] { return &dropAgg[N]{} }
-
-func (s *dropAgg[N]) Aggregate(N, *attribute.Set) {}
-
-func (s *dropAgg[N]) Aggregations() []Aggregation { return nil }

From c7cfda1b820e6468a42eedba9e2f8e33a6724c95 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Thu, 23 Jun 2022 14:12:13 -0700
Subject: [PATCH 24/25] Fix lint

---
 sdk/metric/internal/aggregator.go              | 2 +-
 sdk/metric/internal/aggregator_example_test.go | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/sdk/metric/internal/aggregator.go b/sdk/metric/internal/aggregator.go
index 63489f1ae8b..089f9c9fdea 100644
--- a/sdk/metric/internal/aggregator.go
+++ b/sdk/metric/internal/aggregator.go
@@ -25,7 +25,7 @@ type Aggregator[N int64 | float64] interface {
 	// into an aggregation.
 	Aggregate(measurement N, attr *attribute.Set)
 
-	// Aggregations retuns a slice of Aggregation, one per each attribute set
+	// Aggregations returns a slice of Aggregation, one per each attribute set
 	// used to scope measurement aggregation, and ends an aggregation cycle.
 	Aggregations() []Aggregation
 }
diff --git a/sdk/metric/internal/aggregator_example_test.go b/sdk/metric/internal/aggregator_example_test.go
index 04db712016a..34f59c01d97 100644
--- a/sdk/metric/internal/aggregator_example_test.go
+++ b/sdk/metric/internal/aggregator_example_test.go
@@ -111,9 +111,9 @@ func Example() {
 	m := meter{}
 	provider := m.SyncInt64()
 
-	provider.Counter("counter example")
-	provider.UpDownCounter("up-down counter example")
-	provider.Histogram("histogram example")
+	_, _ = provider.Counter("counter example")
+	_, _ = provider.UpDownCounter("up-down counter example")
+	_, _ = provider.Histogram("histogram example")
 
 	// Output:
 	// using *internal.cumulativeSum[int64] aggregator for counter

From 3d0d54ee09eee0d7407831576b5ab9be3ad30c85 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <codingalias@gmail.com>
Date: Fri, 24 Jun 2022 08:18:48 -0700
Subject: [PATCH 25/25] Use attribute.Set instead of ptr to it

---
 sdk/metric/internal/aggregation.go             | 2 +-
 sdk/metric/internal/aggregator.go              | 2 +-
 sdk/metric/internal/aggregator_example_test.go | 2 +-
 sdk/metric/internal/histogram.go               | 2 +-
 sdk/metric/internal/lastvalue.go               | 2 +-
 sdk/metric/internal/sum.go                     | 2 +-
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/sdk/metric/internal/aggregation.go b/sdk/metric/internal/aggregation.go
index 4149f2672cb..f161d2debbf 100644
--- a/sdk/metric/internal/aggregation.go
+++ b/sdk/metric/internal/aggregation.go
@@ -33,7 +33,7 @@ type Aggregation struct {
 	Timestamp uint64
 
 	// Attributes are the unique dimensions Value describes.
-	Attributes *attribute.Set
+	Attributes attribute.Set
 
 	// Value is the summarization of the measurements made.
 	Value value
diff --git a/sdk/metric/internal/aggregator.go b/sdk/metric/internal/aggregator.go
index 089f9c9fdea..df8b59e84bb 100644
--- a/sdk/metric/internal/aggregator.go
+++ b/sdk/metric/internal/aggregator.go
@@ -23,7 +23,7 @@ import "go.opentelemetry.io/otel/attribute"
 type Aggregator[N int64 | float64] interface {
 	// Aggregate records the measurement, scoped by attr, and aggregates it
 	// into an aggregation.
-	Aggregate(measurement N, attr *attribute.Set)
+	Aggregate(measurement N, attr attribute.Set)
 
 	// Aggregations returns a slice of Aggregation, one per each attribute set
 	// used to scope measurement aggregation, and ends an aggregation cycle.
diff --git a/sdk/metric/internal/aggregator_example_test.go b/sdk/metric/internal/aggregator_example_test.go
index 34f59c01d97..47fe2253818 100644
--- a/sdk/metric/internal/aggregator_example_test.go
+++ b/sdk/metric/internal/aggregator_example_test.go
@@ -101,7 +101,7 @@ func (p *syncInt64Provider) Histogram(string, ...instrument.Option) (syncint64.H
 type inst struct {
 	instrument.Synchronous
 
-	aggregateFunc func(int64, *attribute.Set)
+	aggregateFunc func(int64, attribute.Set)
 }
 
 func (inst) Add(context.Context, int64, ...attribute.KeyValue)    {}
diff --git a/sdk/metric/internal/histogram.go b/sdk/metric/internal/histogram.go
index f25e9aa7430..6931c01f344 100644
--- a/sdk/metric/internal/histogram.go
+++ b/sdk/metric/internal/histogram.go
@@ -28,7 +28,7 @@ type histogram[N int64 | float64] struct {
 	// TODO(#2970): implement.
 }
 
-func (s *histogram[N]) Aggregate(value N, attr *attribute.Set) {
+func (s *histogram[N]) Aggregate(value N, attr attribute.Set) {
 	// TODO(#2970): implement.
 }
 
diff --git a/sdk/metric/internal/lastvalue.go b/sdk/metric/internal/lastvalue.go
index b4e5fa51590..986a2313ad0 100644
--- a/sdk/metric/internal/lastvalue.go
+++ b/sdk/metric/internal/lastvalue.go
@@ -30,7 +30,7 @@ func NewLastValue[N int64 | float64]() Aggregator[N] {
 	return &lastValue[N]{}
 }
 
-func (s *lastValue[N]) Aggregate(value N, attr *attribute.Set) {
+func (s *lastValue[N]) Aggregate(value N, attr attribute.Set) {
 	// TODO(#2971): implement.
 }
 
diff --git a/sdk/metric/internal/sum.go b/sdk/metric/internal/sum.go
index 6315bf70d44..6d01183fb03 100644
--- a/sdk/metric/internal/sum.go
+++ b/sdk/metric/internal/sum.go
@@ -24,7 +24,7 @@ type sum[N int64 | float64] struct {
 	// TODO(#2972): implement.
 }
 
-func (s *sum[N]) Aggregate(value N, attr *attribute.Set) {
+func (s *sum[N]) Aggregate(value N, attr attribute.Set) {
 	// TODO(#2972): implement.
 }