feat: lint examples (open-telemetry#649)

* refactor: use a single eslintrc for all examples folders

furthermore, override the strict rule that ships with airbnb

* fix: turn off no-use-before-define

* fix: install eslint in ci container

Co-Authored-By: Daniel Dyla <dyladan@users.noreply.github.com>

* fix: ignore uninstalled packages lint errors

We will not want to install all examples in CI

Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>
Co-authored-by: Mayur Kale <mayurkale@google.com>

.circleci/config.yml

@@ -172,6 +172,12 @@ jobs:
           root: packages/opentelemetry-types/docs
           paths:
             - out
+      - run:
+          name: Install minimal modules to lint examples
+          command: npm i -D eslint eslint-plugin-import eslint-config-airbnb-base
+      - run:
+          name: Lint examples
+          command: npm run lint-examples
   docs-deploy:
     docker:
       - image: node:12

examples/.eslintrc

@@ -0,0 +1,16 @@
+{
+  "env": {
+    "node": true
+  },
+  "extends": "airbnb-base",
+  "parserOptions": {
+    "sourceType": "script"
+  },
+  "rules": {
+    "strict": ["error", "global"],
+    "no-use-before-define": ["error", "nofunc"],
+    "no-console": "off",
+    "import/no-unresolved": "off",
+    "no-unused-vars": ["error", { "argsIgnorePattern": "^_" }]
+  }
+}

examples/basic-tracer-node/index.js

@@ -1,11 +1,13 @@
+'use strict';
+
 const opentelemetry = require('@opentelemetry/core');
 const { BasicTracerRegistry, SimpleSpanProcessor } = require('@opentelemetry/tracing');
 const { JaegerExporter } = require('@opentelemetry/exporter-jaeger');
 const { ZipkinExporter } = require('@opentelemetry/exporter-zipkin');
-const { CollectorExporter } =  require('@opentelemetry/exporter-collector');
+const { CollectorExporter } = require('@opentelemetry/exporter-collector');
 
 const options = {
-  serviceName: 'basic-service'
+  serviceName: 'basic-service',
 };
 
 // Initialize an exporter depending on how we were started
@@ -27,15 +29,15 @@ registry.addSpanProcessor(new SimpleSpanProcessor(exporter));
 
 // Initialize the OpenTelemetry APIs to use the BasicTracerRegistry bindings
 opentelemetry.initGlobalTracerRegistry(registry);
-const tracer = opentelemetry.getTracer('example-basic-tracer-node')
+const tracer = opentelemetry.getTracer('example-basic-tracer-node');
 
 // Create a span. A span must be closed.
-const span = tracer.startSpan('main');
-for (let i = 0; i < 10; i++) {
-  doWork(span);
+const parentSpan = tracer.startSpan('main');
+for (let i = 0; i < 10; i += 1) {
+  doWork(parentSpan);
 }
 // Be sure to end the span.
-span.end();
+parentSpan.end();
 
 // flush and close the connection.
 exporter.shutdown();
@@ -44,11 +46,13 @@ function doWork(parent) {
   // Start another span. In this example, the main method already started a
   // span, so that'll be the parent span, and this will be a child span.
   const span = tracer.startSpan('doWork', {
-    parent: parent
+    parent,
   });
 
   // simulate some random work.
-  for (let i = 0; i <= Math.floor(Math.random() * 40000000); i++) { }
+  for (let i = 0; i <= Math.floor(Math.random() * 40000000); i += 1) {
+    // empty
+  }
 
   // Set attributes to the span.
   span.setAttribute('key', 'value');

examples/basic-tracer-node/multi_exporter.js

@@ -1,39 +1,44 @@
+'use strict';
+
 const opentelemetry = require('@opentelemetry/core');
 const { BasicTracerRegistry, BatchSpanProcessor, SimpleSpanProcessor } = require('@opentelemetry/tracing');
 const { JaegerExporter } = require('@opentelemetry/exporter-jaeger');
 const { ZipkinExporter } = require('@opentelemetry/exporter-zipkin');
-const { CollectorExporter } =  require('@opentelemetry/exporter-collector');
+const { CollectorExporter } = require('@opentelemetry/exporter-collector');
 
 const registry = new BasicTracerRegistry();
 
-const zipkinExporter = new ZipkinExporter({serviceName: 'basic-service'});
+const zipkinExporter = new ZipkinExporter({ serviceName: 'basic-service' });
 const jaegerExporter = new JaegerExporter({
   serviceName: 'basic-service',
 });
-const collectorExporter = new CollectorExporter({serviceName: 'basic-service'});
+const collectorExporter = new CollectorExporter({ serviceName: 'basic-service' });
 
 // It is recommended to use this BatchSpanProcessor for better performance
 // and optimization, especially in production.
 registry.addSpanProcessor(new BatchSpanProcessor(zipkinExporter, {
-  bufferSize: 10 // This is added for example, default size is 100.
+  // This is added for example, default size is 100.
+  bufferSize: 10,
 }));
+
+const tracer = opentelemetry.getTracer('default');
+
 tracer.addSpanProcessor(new BatchSpanProcessor(jaegerExporter), {
-  bufferSize: 10
+  bufferSize: 10,
 });
 
 registry.addSpanProcessor(new SimpleSpanProcessor(collectorExporter));
 
 // Initialize the OpenTelemetry APIs to use the BasicTracerRegistry bindings
 opentelemetry.initGlobalTracerRegistry(registry);
-const tracer = opentelemetry.getTracer('default');
 
 // Create a span. A span must be closed.
-const span = tracer.startSpan('main');
-for (let i = 0; i < 10; i++) {
-  doWork(span);
+const parentSpan = tracer.startSpan('main');
+for (let i = 0; i < 10; i += 1) {
+  doWork(parentSpan);
 }
 // Be sure to end the span.
-span.end();
+parentSpan.end();
 
 // flush and close the connection.
 zipkinExporter.shutdown();
@@ -44,11 +49,13 @@ function doWork(parent) {
   // Start another span. In this example, the main method already started a
   // span, so that'll be the parent span, and this will be a child span.
   const span = tracer.startSpan('doWork', {
-    parent: parent
+    parent,
   });
 
   // simulate some random work.
-  for (let i = 0; i <= Math.floor(Math.random() * 40000000); i++) { }
+  for (let i = 0; i <= Math.floor(Math.random() * 40000000); i += 1) {
+    // empty
+  }
 
   // Set attributes to the span.
   span.setAttribute('key', 'value');

examples/dns/client.js

@@ -1,42 +1,34 @@
 'use strict';
 
-const opentelemetry = require('@opentelemetry/core');
-const config = require('./setup');
-
-/**
- * The trace instance needs to be initialized first, if you want to enable
- * automatic tracing for built-in plugins (DNS in this case).
- */
-config.setupTracerAndExporters('dns-client-service');
-
+const tracer = require('./tracer')('example-dns');
+// eslint-disable-next-line import/order
 const dns = require('dns').promises;
-const tracer = opentelemetry.getTracer('example-dns');
 
 /** A function which makes a dns lookup and handles response. */
 function makeLookup() {
-    // span corresponds to dns lookup. Here, we have manually created
-    // the span, which is created to track work that happens outside of the
-    // dns lookup query.
-    const span = tracer.startSpan('dnsLookup');
-    tracer.withSpan(span, async () => {
-        try {
-            await dns.lookup('montreal.ca');
-        } catch (error) {
-            span.setAttributes({
-                'error.name': error.name,
-                'error.message': error.message
-            });
-        }finally{
-            console.log(`traceid: ${span.context().traceId}`);
-            span.end();
-        }
-    });
+  // span corresponds to dns lookup. Here, we have manually created
+  // the span, which is created to track work that happens outside of the
+  // dns lookup query.
+  const span = tracer.startSpan('dnsLookup');
+  tracer.withSpan(span, async () => {
+    try {
+      await dns.lookup('montreal.ca');
+    } catch (error) {
+      span.setAttributes({
+        'error.name': error.name,
+        'error.message': error.message,
+      });
+    } finally {
+      console.log(`traceid: ${span.context().traceId}`);
+      span.end();
+    }
+  });
 
-    // The process must live for at least the interval past any traces that
-    // must be exported, or some risk being lost if they are recorded after the
-    // last export.
-    console.log('Sleeping 5 seconds before shutdown to ensure all records are flushed.')
-    setTimeout(() => { console.log('Completed.'); }, 5000);
+  // The process must live for at least the interval past any traces that
+  // must be exported, or some risk being lost if they are recorded after the
+  // last export.
+  console.log('Sleeping 5 seconds before shutdown to ensure all records are flushed.');
+  setTimeout(() => { console.log('Completed.'); }, 5000);
 }
 
 makeLookup();

examples/dns/tracer.js

@@ -0,0 +1,40 @@
+'use strict';
+
+const opentelemetry = require('@opentelemetry/core');
+const { NodeTracerRegistry } = require('@opentelemetry/node');
+const { SimpleSpanProcessor } = require('@opentelemetry/tracing');
+const { JaegerExporter } = require('@opentelemetry/exporter-jaeger');
+const { ZipkinExporter } = require('@opentelemetry/exporter-zipkin');
+
+const EXPORTER = process.env.EXPORTER || '';
+
+module.exports = (serviceName) => {
+  const registry = new NodeTracerRegistry({
+    plugins: {
+      dns: {
+        enabled: true,
+        path: '@opentelemetry/plugin-dns',
+        // Avoid dns lookup loop with http zipkin calls
+        ignoreHostnames: ['localhost'],
+      },
+    },
+  });
+
+  let exporter;
+  if (EXPORTER.toLowerCase().startsWith('z')) {
+    exporter = new ZipkinExporter({
+      serviceName,
+    });
+  } else {
+    exporter = new JaegerExporter({
+      serviceName,
+    });
+  }
+
+  registry.addSpanProcessor(new SimpleSpanProcessor(exporter));
+
+  // Initialize the OpenTelemetry APIs to use the BasicTracerRegistry bindings
+  opentelemetry.initGlobalTracerRegistry(registry);
+
+  return opentelemetry.getTracer();
+};

examples/grpc/client.js

@@ -1,20 +1,12 @@
 'use strict';
 
-const opentelemetry = require('@opentelemetry/core');
-const config = require('./setup');
-
-/**
- * The trace instance needs to be initialized first, if you want to enable
- * automatic tracing for built-in plugins (gRPC in this case).
- */
-config.setupTracerAndExporters('grpc-client-service');
-
+const tracer = require('./tracer')('example-grpc-client');
+// eslint-disable-next-line import/order
 const grpc = require('grpc');
-
 const messages = require('./helloworld_pb');
 const services = require('./helloworld_grpc_pb');
+
 const PORT = 50051;
-const tracer = opentelemetry.getTracer('example-grpc-client');
 
 /** A function which makes requests and handles response. */
 function main() {
@@ -26,17 +18,18 @@ function main() {
     console.log('Client traceId ', span.context().traceId);
     const client = new services.GreeterClient(
       `localhost:${PORT}`,
-      grpc.credentials.createInsecure()
+      grpc.credentials.createInsecure(),
     );
     const request = new messages.HelloRequest();
     let user;
     if (process.argv.length >= 3) {
+      // eslint-disable-next-line prefer-destructuring
       user = process.argv[2];
     } else {
       user = 'world';
     }
     request.setName(user);
-    client.sayHello(request, function(err, response) {
+    client.sayHello(request, (err, response) => {
       span.end();
       if (err) throw err;
       console.log('Greeting:', response.getMessage());
@@ -46,7 +39,7 @@ function main() {
   // The process must live for at least the interval past any traces that
   // must be exported, or some risk being lost if they are recorded after the
   // last export.
-  console.log('Sleeping 5 seconds before shutdown to ensure all records are flushed.')
+  console.log('Sleeping 5 seconds before shutdown to ensure all records are flushed.');
   setTimeout(() => { console.log('Completed.'); }, 5000);
 }