Service: Support configuring host and port thru config and environment variables (#40)

Support configuring service host and port thru config and 
environment variables.

Co-authored-by: Marcus Efraimsson <[email protected]>

Author: kaey

default.json

@@ -1,5 +1,6 @@
 {
   "service": {
+    "host": null,
     "port": 8081,
     "metrics": {
       "enabled": false,

dev.json

@@ -1,5 +1,6 @@
 {
   "service": {
+    "host": "localhost",
     "port": 8081,
     "metrics": {
       "enabled": true,

docs/remote_rendering_using_docker.md

@@ -8,6 +8,22 @@ The docker image are published at [Docker Hub](https://hub.docker.com/r/grafana/
 
 You can override certain settings by using environment variables.
 
+**HTTP host:**
+
+Change the listening host of the HTTP server. Default is unset and will use the local host.
+
+```bash
+export HTTP_HOST=localhost
+```
+
+**HTTP port:**
+
+Change the listening port of the HTTP server. Default is `8081`. Setting `0` will automatically assign a port not in use.
+
+```bash
+export HTTP_PORT=0
+```
+
 **Default timezone:**
 
 Instruct headless Chrome to use a default timezone when not provided by Grafana, .e.g. when rendering panel image of alert. See [ICU’s metaZones.txt](https://cs.chromium.org/chromium/src/third_party/icu/source/data/misc/metaZones.txt?rcl=faee8bc70570192d82d2978a71e2a615788597d1) for a list of supported timezone IDs.

src/app.ts

@@ -85,6 +85,14 @@ function populateServiceConfigFromEnv(config: ServiceConfig, env: NodeJS.Process
     config.rendering.timezone = env['TZ'];
   }
 
+  if (env['HTTP_HOST']) {
+    config.service.host = env['HTTP_HOST'];
+  }
+
+  if (env['HTTP_PORT']) {
+    config.service.port = parseInt(env['HTTP_PORT'] as string, 10);
+  }
+
   if (env['IGNORE_HTTPS_ERRORS']) {
     config.rendering.ignoresHttpsErrors = env['IGNORE_HTTPS_ERRORS'] === 'true';
   }

src/config.ts

@@ -22,6 +22,7 @@ export interface MetricsConfig {
 
 export interface ServiceConfig {
   service: {
+    host?: string;
     port: number;
     metrics: MetricsConfig;
   };
@@ -52,6 +53,7 @@ const defaultRenderingConfig: RenderingConfig = {
 
 export const defaultServiceConfig: ServiceConfig = {
   service: {
+    host: undefined,
     port: 8081,
     metrics: {
       enabled: false,

src/service/http-server.ts

@@ -1,3 +1,5 @@
+import * as http from 'http';
+import * as net from 'net';
 import express = require('express');
 import { Logger } from '../logger';
 import { Browser } from '../browser';
@@ -35,8 +37,17 @@ export class HttpServer {
       this.log.info(`Ignoring HTTPS errors`);
     }
 
-    this.app.listen(this.config.service.port);
-    this.log.info(`HTTP Server started, listening on ${this.config.service.port}`);
+    if (this.config.service.host) {
+      const server = this.app.listen(this.config.service.port, this.config.service.host, () => {
+        const info = server.address() as net.AddressInfo;
+        this.log.info(`HTTP Server started, listening at http://${this.config.service.host}:${info.port}`);
+      });
+    } else {
+      const server = this.app.listen(this.config.service.port, () => {
+        const info = server.address() as net.AddressInfo;
+        this.log.info(`HTTP Server started, listening at http://localhost:${info.port}`);
+      });
+    }
 
     const browserInfo = new promClient.Gauge({
       name: 'grafana_image_renderer_browser_info',