From 239bfdd3414768133549205c05d15114bc733578 Mon Sep 17 00:00:00 2001
From: naseemkullah <naseem@transit.app>
Date: Wed, 20 Jan 2021 20:52:15 -0500
Subject: [PATCH] feat: add prometheus exporter host and port env vars

Signed-off-by: naseemkullah <naseem@transit.app>
---
 .../src/PrometheusExporter.ts                 | 25 +++++++++++------
 .../src/export/types.ts                       |  5 ++++
 .../test/PrometheusExporter.test.ts           | 27 +++++++++++++++++--
 3 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts b/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts
index d47745980ca..05b8cc4e9b2 100644
--- a/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts
+++ b/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts
@@ -26,16 +26,17 @@ import * as url from 'url';
 import { ExporterConfig } from './export/types';
 import { PrometheusSerializer } from './PrometheusSerializer';
 import { PrometheusLabelsBatcher } from './PrometheusLabelsBatcher';
-
 export class PrometheusExporter implements MetricExporter {
   static readonly DEFAULT_OPTIONS = {
-    port: 9464,
+    host: process.env.OTEL_EXPORTER_PROMETHEUS_HOST ?? '0.0.0.0',
+    port: Number(process.env.OTEL_EXPORTER_PROMETHEUS_PORT) ?? 9464,
     endpoint: '/metrics',
     prefix: '',
     appendTimestamp: true,
   };
 
   private readonly _logger: api.Logger;
+  private readonly _host: string;
   private readonly _port: number;
   private readonly _endpoint: string;
   private readonly _server: Server;
@@ -55,6 +56,7 @@ export class PrometheusExporter implements MetricExporter {
    */
   constructor(config: ExporterConfig = {}, callback?: () => void) {
     this._logger = config.logger || new api.NoopLogger();
+    this._host = config.host || PrometheusExporter.DEFAULT_OPTIONS.host;
     this._port = config.port || PrometheusExporter.DEFAULT_OPTIONS.port;
     this._prefix = config.prefix || PrometheusExporter.DEFAULT_OPTIONS.prefix;
     this._appendTimestamp =
@@ -148,12 +150,19 @@ export class PrometheusExporter implements MetricExporter {
    */
   startServer(): Promise<void> {
     return new Promise(resolve => {
-      this._server.listen(this._port, () => {
-        this._logger.debug(
-          `Prometheus exporter started on port ${this._port} at endpoint ${this._endpoint}`
-        );
-        resolve();
-      });
+      this._server.listen(
+        {
+          port: this._port,
+          host: this._host,
+          path: this._endpoint,
+        },
+        () => {
+          this._logger.debug(
+            `Prometheus exporter started on port ${this._host}/${this._port} at endpoint ${this._endpoint}`
+          );
+          resolve();
+        }
+      );
     });
   }
 
diff --git a/packages/opentelemetry-exporter-prometheus/src/export/types.ts b/packages/opentelemetry-exporter-prometheus/src/export/types.ts
index 40efc413cfd..a60ba6d23f3 100644
--- a/packages/opentelemetry-exporter-prometheus/src/export/types.ts
+++ b/packages/opentelemetry-exporter-prometheus/src/export/types.ts
@@ -39,6 +39,11 @@ export interface ExporterConfig {
    */
   endpoint?: string;
 
+  /**
+   * @default '0.0.0.0'
+   */
+  host?: string;
+
   /**
    * Port number for Prometheus exporter server
    *
diff --git a/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts b/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts
index cb5ccb93bca..47cc2a2c1ec 100644
--- a/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts
+++ b/packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts
@@ -33,6 +33,11 @@ describe('PrometheusExporter', () => {
   mockAggregator(LastValueAggregator);
   mockAggregator(HistogramAggregator);
 
+  afterEach(() => {
+    delete process.env.OTEL_EXPORTER_PROMETHEUS_HOST;
+    delete process.env.OTEL_EXPORTER_PROMETHEUS_PORT;
+  });
+
   describe('constructor', () => {
     it('should construct an exporter', done => {
       const exporter = new PrometheusExporter();
@@ -88,7 +93,8 @@ describe('PrometheusExporter', () => {
       });
     });
 
-    it('it should listen on a custom port and endpoint if provided', done => {
+    it('it should listen on a custom host, port and endpoint if provided', done => {
+      const host = 'prometheus.exporter.com';
       const port = 9991;
       const endpoint = '/metric';
 
@@ -98,7 +104,7 @@ describe('PrometheusExporter', () => {
           endpoint,
         },
         () => {
-          const url = `http://localhost:${port}${endpoint}`;
+          const url = `http://${host}:${port}${endpoint}`;
           http.get(url, (res: any) => {
             assert.strictEqual(res.statusCode, 200);
             exporter.shutdown().then(() => {
@@ -109,6 +115,23 @@ describe('PrometheusExporter', () => {
       );
     });
 
+    it('it should listen on environmentally set host and port', done => {
+      const envSetHost = 'env-set-host';
+      const envSetPort = '1234';
+      process.env.OTEL_EXPORTER_PROMETHEUS_HOST = envSetHost;
+      process.env.OTEL_EXPORTER_PROMETHEUS_PORT = envSetPort;
+
+      const exporter = new PrometheusExporter({}, () => {
+        const url = `http://${envSetHost}:${envSetPort}/metrics`;
+        http.get(url, (res: any) => {
+          assert.strictEqual(res.statusCode, 200);
+          exporter.shutdown().then(() => {
+            return done();
+          });
+        });
+      });
+    });
+
     it('it should not require endpoints to start with a slash', done => {
       const port = 9991;
       const endpoint = 'metric';