diff --git a/communication/src/logging.rs b/communication/src/logging.rs
index 1ce8608a1..0b4c2b5f2 100644
--- a/communication/src/logging.rs
+++ b/communication/src/logging.rs
@@ -4,5 +4,5 @@ use timely_logging::{CommsEvent, CommsSetup};
 pub use timely_logging::CommunicationEvent;
 pub use timely_logging::SerializationEvent;
 
-/// TODO(andreal)
+/// A log writer for a communication thread.
 pub type CommsLogger = Rc<::timely_logging::BufferingLogger<CommsSetup, CommsEvent>>;
diff --git a/logging/src/lib.rs b/logging/src/lib.rs
index 3ba8c5803..72b3b8af4 100644
--- a/logging/src/lib.rs
+++ b/logging/src/lib.rs
@@ -29,17 +29,6 @@ pub fn get_precise_time_ns() -> u64 {
     (time::precise_time_ns() as i64 - delta) as u64
 }
 
-// /// TODO(andreal)
-// fn initialize_precise_time_ns() {
-//     unsafe {
-//         precise_time_ns_delta = Some({
-//             let wall_time = time::get_time();
-//             let wall_time_ns = wall_time.nsec as i64 + wall_time.sec * 1000000000;
-//             time::precise_time_ns() as i64 - wall_time_ns
-//         });
-//     }
-// }
-
 /// Logging methods
 pub trait Logger {
     /// The type of loggable record.
diff --git a/src/dataflow/scopes/child.rs b/src/dataflow/scopes/child.rs
index 2f7c6ce0a..1df516b97 100644
--- a/src/dataflow/scopes/child.rs
+++ b/src/dataflow/scopes/child.rs
@@ -18,7 +18,7 @@ pub struct Child<'a, G: ScopeParent, T: Timestamp> {
     pub subgraph: &'a RefCell<SubgraphBuilder<G::Timestamp, T>>,
     /// A copy of the child's parent scope.
     pub parent:   G,
-    /// TODO(andreal)
+    /// The log writer for this scope.
     pub logging:  Logger,
 }
 
diff --git a/src/dataflow/scopes/mod.rs b/src/dataflow/scopes/mod.rs
index 4b7665385..687c3fee2 100644
--- a/src/dataflow/scopes/mod.rs
+++ b/src/dataflow/scopes/mod.rs
@@ -76,6 +76,6 @@ pub trait Scope: ScopeParent {
     /// ```
     fn scoped<T: Timestamp, R, F:FnOnce(&mut Child<Self, T>)->R>(&mut self, func: F) -> R;
 
-    /// TODO(andreal)
+    /// Obtains the logger associated with this scope.
     fn logging(&self) -> Logger;
 }
diff --git a/src/dataflow/scopes/root.rs b/src/dataflow/scopes/root.rs
index df2b62030..b651d7bf4 100644
--- a/src/dataflow/scopes/root.rs
+++ b/src/dataflow/scopes/root.rs
@@ -52,7 +52,7 @@ impl<A: Allocate> Root<A> {
         // discard completed dataflows.
         self.dataflows.borrow_mut().retain(|dataflow| dataflow.active());
 
-        // TODO(andreal) flush logs?
+        // TODO(andreal) do we want to flush logs here?
 
         active
     }
diff --git a/src/logging.rs b/src/logging.rs
index 719e82b6c..46876da74 100644
--- a/src/logging.rs
+++ b/src/logging.rs
@@ -25,10 +25,10 @@ use timely_logging::LoggerBatch;
 type LogMessage = (u64, EventsSetup, LogEvent);
 type CommsMessage = (u64, CommsSetup, CommsEvent);
 
-/// TODO(andreal)
+/// A log writer.
 pub type Logger = Rc<BufferingLogger<EventsSetup, LogEvent>>;
 
-/// TODO(andreal)
+/// A log writer that does not log anything.
 pub fn new_inactive_logger() -> Logger {
     BufferingLogger::<(), ()>::new_inactive()
 }
@@ -83,37 +83,22 @@ impl LogManager {
     }
 }
 
-struct SharedVec {
-    inner: Arc<Mutex<Vec<u8>>>,
+struct SharedEventWriter<T, D, W: Write> {
+    inner: Arc<Mutex<EventWriter<T, D, W>>>,
 }
 
-impl SharedVec {
-    pub fn new(inner: Arc<Mutex<Vec<u8>>>) -> Self {
-        SharedVec { 
-            inner: inner,
+impl<T, D, W: Write> Clone for SharedEventWriter<T, D, W> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
         }
     }
 }
 
-impl Write for SharedVec {
-    fn write(&mut self, data: &[u8]) -> Result<usize, ::std::io::Error> {
-        self.inner.lock().unwrap().extend_from_slice(data);
-        Ok(data.len())
-    }
-
-    fn flush(&mut self) -> Result<(), ::std::io::Error> {
-        Ok(())
-    }
-}
-
-struct SharedEventWriter<T, D, W: Write> {
-    inner: Mutex<EventWriter<T, D, W>>,
-}
-
 impl<T, D, W: Write> SharedEventWriter<T, D, W> {
     fn new(w: W) -> Self {
         SharedEventWriter {
-            inner: Mutex::new(EventWriter::new(w)),
+            inner: Arc::new(Mutex::new(EventWriter::new(w))),
         }
     }
 }
@@ -125,7 +110,7 @@ impl<T: Abomonation+Debug, D: Abomonation+Debug, W: Write> EventPusher<T, D> for
     }
 }
 
-/// TODO(andreal)
+/// An handle to the LogManager that constructs a filter for the log records.
 pub struct FilteredLogManager<S, E> {
     log_manager: Arc<Mutex<LogManager>>,
     filter: Arc<Fn(&S)->bool+Send+Sync>,
@@ -133,8 +118,10 @@ pub struct FilteredLogManager<S, E> {
 }
 
 impl FilteredLogManager<EventsSetup, LogEvent> {
-    /// TODO(andreal)
-    pub fn to_tcp_socket(&mut self) {
+    /// Send the selected timely events to one tcp socket per log sender.
+    ///
+    /// Destination can be set with the TIMELY_COMM_LOG_TARGET environment variable.
+    pub fn to_tcp_sockets(&mut self) {
         let target: String = ::std::env::var("TIMELY_LOG_TARGET").expect("no $TIMELY_LOG_TARGET, e.g. 127.0.0.1:34254");
 
         // let writer = SharedEventWriter::new(writer);
@@ -145,24 +132,20 @@ impl FilteredLogManager<EventsSetup, LogEvent> {
         self.log_manager.lock().unwrap().add_timely_subscription(self.filter.clone(), pusher);
     }
 
-    // /// TODO(andreal)
-    // pub fn to_bufs(&mut self) -> Vec<Arc<Mutex<Vec<u8>>>> {
-    //     let mut vecs = Vec::new();
-
-    //     for i in 0..4 {
-    //         let buf = Arc::new(Mutex::new(Vec::<u8>::with_capacity(4_000_000_000)));
-    //         let writer = SharedEventWriter::new(SharedVec::new(buf.clone()));
-    //         let pusher: Arc<EventPusher<Product<RootTimestamp, u64>, LogMessage>+Send+Sync> = Arc::new(writer);
-    //         self.log_manager.lock().unwrap().add_timely_subscription(Arc::new(move |s| s.index == i), pusher);
-    //         vecs.push(buf);
-    //     }
-
-    //     vecs
-    // }
+    /// Send the selected timely events to a shared tcp socket.
+    ///
+    /// Destination can be set with the TIMELY_COMM_LOG_TARGET environment variable.
+    pub fn to_shared_tcp_socket(&mut self) {
+        let target: String = ::std::env::var("TIMELY_LOG_TARGET").expect("no $TIMELY_LOG_TARGET, e.g. 127.0.0.1:34254");
+        let pusher = Box::new(SharedEventWriter::new(TcpStream::connect(target.clone()).expect("failed to connect to logging destination")));
+        self.log_manager.lock().unwrap().add_timely_subscription(self.filter.clone(), Arc::new(move || pusher.clone()));
+    }
 }
 
 impl FilteredLogManager<CommsSetup, CommsEvent> {
-    /// TODO(andreal)
+    /// Send the selected communication events to a tcp socket.
+    ///
+    /// Destination can be set with the TIMELY_COMM_LOG_TARGET environment variable.
     pub fn to_tcp_socket(&mut self) {
         let comm_target = ::std::env::var("TIMELY_COMM_LOG_TARGET").expect("no $TIMELY_COMM_LOG_TARGET, e.g. 127.0.0.1:34255");
 
@@ -175,7 +158,7 @@ impl FilteredLogManager<CommsSetup, CommsEvent> {
 }
 
 impl LogManager {
-    /// TODO(andreal)
+    /// Constructs a new LogManager.
     pub fn new() -> Arc<Mutex<Self>> {
         Arc::new(Mutex::new(LogManager {
             timely_logs: HashMap::new(),
@@ -186,17 +169,16 @@ impl LogManager {
     }
 }
 
-/// TODO(andreal)
+/// Functions to construct log filters. 
 pub trait LogFilter {
-    /// TODO(andreal)
+    /// Get a `FilteredLogManager` for all workers.
     fn workers(&mut self) -> FilteredLogManager<EventsSetup, LogEvent>;
 
-    /// TODO(andreal)
+    /// Get a `FilteredLogManager` for all communication threads.
     fn comms(&mut self) -> FilteredLogManager<CommsSetup, CommsEvent>;
 }
 
 impl LogFilter for Arc<Mutex<LogManager>> {
-    /// TODO(andreal)
     #[inline] fn workers(&mut self) -> FilteredLogManager<EventsSetup, LogEvent> {
         FilteredLogManager {
             log_manager: self.clone(),
@@ -205,7 +187,6 @@ impl LogFilter for Arc<Mutex<LogManager>> {
         }
     }
  
-    /// TODO(andreal)
     #[inline] fn comms(&mut self) -> FilteredLogManager<CommsSetup, CommsEvent> {
         FilteredLogManager {
             log_manager: self.clone(),
@@ -215,11 +196,11 @@ impl LogFilter for Arc<Mutex<LogManager>> {
     }
 }
 
-/// TODO(andreal)
+/// Shared wrapper for log writer constructors.
 pub struct LoggerConfig {
-    /// TODO(andreal)
+    /// Log writer constructors.
     pub timely_logging: Arc<Fn(EventsSetup)->Rc<BufferingLogger<EventsSetup, LogEvent>>+Send+Sync>,
-    /// TODO(andreal)
+    /// Log writer constructors for communication.
     pub communication_logging: Arc<Fn(CommsSetup)->Rc<BufferingLogger<CommsSetup, CommsEvent>>+Send+Sync>,
 }
 
@@ -249,7 +230,7 @@ impl LoggerConfig {
         event_manager
     }
 
-    /// TODO(andreal)
+    /// Makes a new `LoggerConfig` wrapper from a `LogManager`.
     pub fn new(log_manager: Arc<Mutex<LogManager>>) -> Self {
         let timely_logging_manager = log_manager.clone();
         let communication_logging_manager = log_manager;
@@ -257,7 +238,6 @@ impl LoggerConfig {
             timely_logging: Arc::new(move |events_setup: EventsSetup| {
                 let subscription_manager = LoggerConfig::register_timely_logger(
                     &mut timely_logging_manager.lock().unwrap(), events_setup);
-                //eprintln!("registered timely logger: {:?}", events_setup);
                 Rc::new(BufferingLogger::new(events_setup, Box::new(move |data| {
                     subscription_manager.lock().expect("cannot lock mutex").publish_batch(data);
                 })))
@@ -265,7 +245,6 @@ impl LoggerConfig {
             communication_logging: Arc::new(move |comms_setup: CommsSetup| {
                 let subscription_manager = LoggerConfig::register_comms_logger(
                     &mut communication_logging_manager.lock().unwrap(), comms_setup);
-                //eprintln!("registered comm logger: {:?}", comms_setup);
                 Rc::new(BufferingLogger::new(comms_setup, Box::new(move |data| {
                     subscription_manager.lock().expect("cannot lock mutex").publish_batch(data);
                 })))
diff --git a/src/progress/nested/subgraph.rs b/src/progress/nested/subgraph.rs
index de864bf3f..b8902d748 100644
--- a/src/progress/nested/subgraph.rs
+++ b/src/progress/nested/subgraph.rs
@@ -946,11 +946,9 @@ impl<T: Timestamp> PerOperatorState<T> {
                 id: self.id, start_stop: ::timely_logging::StartStop::Start
             }));
 
-            // TODO(andreal) formerly behind "logging" feature flag {
-            //     assert!(self.consumed_buffer.iter_mut().all(|cm| cm.is_empty()));
-            //     assert!(self.internal_buffer.iter_mut().all(|cm| cm.is_empty()));
-            //     assert!(self.produced_buffer.iter_mut().all(|cm| cm.is_empty()));
-            // }
+            debug_assert!(self.consumed_buffer.iter_mut().all(|cm| cm.is_empty()));
+            debug_assert!(self.internal_buffer.iter_mut().all(|cm| cm.is_empty()));
+            debug_assert!(self.produced_buffer.iter_mut().all(|cm| cm.is_empty()));
 
             let result = if let Some(ref mut operator) = self.operator {
                 operator.pull_internal_progress(