Merge branch 'main' into haddas-approver

README.md

@@ -182,6 +182,7 @@ Approvers ([@open-telemetry/js-approvers](https://github.com/orgs/open-telemetry
 - [John Bley](https://github.com/johnbley), Splunk
 - [Marc Pichler](https://github.com/pichlermarc), Dynatrace
 - [Mark Wolff](https://github.com/markwolff), Microsoft
+- [Martin Kuba](https://github.com/martinkuba), Lightstep
 - [Matthew Wear](https://github.com/mwear), LightStep
 - [Naseem K. Ullah](https://github.com/naseemkullah), Transit
 - [Neville Wylie](https://github.com/MSNev), Microsoft

experimental/CHANGELOG.md

@@ -10,6 +10,8 @@ All notable changes to experimental packages in this project will be documented
 
 ### :bug: (Bug Fix)
 
+* fix(prometheus-exporter): add possibility to respond to errors returned by `server.listen()` [#3552](https://github.com/open-telemetry/opentelemetry-js/pull/3402) @pichlermarc
+
 ### :books: (Refine Doc)
 
 ### :house: (Internal)

experimental/packages/opentelemetry-exporter-prometheus/README.md

@@ -25,7 +25,7 @@ const { PrometheusExporter } = require('@opentelemetry/exporter-prometheus');
 const { MeterProvider }  = require('@opentelemetry/sdk-metrics');
 
 // Add your port and startServer to the Prometheus options
-const options = {port: 9464, startServer: true};
+const options = {port: 9464};
 const exporter = new PrometheusExporter(options);
 
 // Creates MeterProvider and installs the exporter as a MetricReader

experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts

@@ -54,7 +54,10 @@ export class PrometheusExporter extends MetricReader {
    * @param config Exporter configuration
    * @param callback Callback to be called after a server was started
    */
-  constructor(config: ExporterConfig = {}, callback?: () => void) {
+  constructor(
+    config: ExporterConfig = {},
+    callback: (error: Error | void) => void = () => {}
+  ) {
     super({
       aggregationSelector: _instrumentType => Aggregation.Default(),
       aggregationTemporalitySelector: _instrumentType =>
@@ -86,9 +89,10 @@ export class PrometheusExporter extends MetricReader {
     ).replace(/^([^/])/, '/$1');
 
     if (config.preventServerStart !== true) {
-      this.startServer()
-        .then(callback)
-        .catch(err => diag.error(err));
+      this.startServer().then(callback, err => {
+        diag.error(err);
+        callback(err);
+      });
     } else if (callback) {
       callback();
     }
@@ -137,7 +141,8 @@ export class PrometheusExporter extends MetricReader {
    * Starts the Prometheus export server
    */
   startServer(): Promise<void> {
-    return new Promise(resolve => {
+    return new Promise((resolve, reject) => {
+      this._server.once('error', reject);
       this._server.listen(
         {
           port: this._port,
@@ -156,7 +161,7 @@ export class PrometheusExporter extends MetricReader {
   /**
    * Request handler that responds with the current state of metrics
    * @param _request Incoming HTTP request of server instance
-   * @param response HTTP response objet used to response to request
+   * @param response HTTP response object used to response to request
    */
   public getMetricsRequestHandler(
     _request: IncomingMessage,

experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts

@@ -74,6 +74,27 @@ describe('PrometheusExporter', () => {
       });
     });
 
+    it('should pass server error to callback when port is already in use', done => {
+      const firstExporter = new PrometheusExporter({}, error => {
+        if (error) {
+          // This should not happen as the port should not be already in use when the test starts.
+          done(error);
+        }
+      });
+      const secondExporter = new PrometheusExporter({}, error => {
+        firstExporter
+          .shutdown()
+          .then(() => secondExporter.shutdown())
+          .then(() =>
+            done(
+              error
+                ? undefined
+                : 'Second exporter should respond with EADDRINUSE but did not pass it to callback'
+            )
+          );
+      });
+    });
+
     it('should not start the server if preventServerStart is passed as an option', () => {
       const exporter = new PrometheusExporter({ preventServerStart: true });
       assert.ok(exporter['_server'].listening === false);