Restart browser if killed on Mermaid

Author: ggrossetie

Diff for: mermaid/src/browser-instance.js

@@ -2,6 +2,8 @@ import puppeteer from 'puppeteer'
 
 import { logger } from './logger.js'
 
+let INSTANCE
+
 const createBrowser = async () => {
   const browser = await puppeteer.launch({
     headless: 'new',
@@ -30,8 +32,9 @@ const createBrowser = async () => {
       '--disable-software-rasterizer'
     ]
   })
-
   const browserProcess = browser.process()
+  logger.info(`Chrome instance launched with pid ${browserProcess.pid}`)
+
   browserProcess.stdout.unpipe()
   browserProcess.stderr.unpipe()
   browserProcess.stdout.on('data', (data) => {
@@ -50,6 +53,9 @@ const createBrowser = async () => {
   })
   browserProcess.on('exit', (code, signal) => {
     logger.error({ code, signal }, 'chrome process exited')
+    browserProcess.kill()
+    browser.close()
+    INSTANCE = undefined
   })
   browserProcess.on('message', (message) => {
     logger.warn({ message }, 'chrome process message')
@@ -60,10 +66,14 @@ const createBrowser = async () => {
     await browser.close()
     throw err
   } finally {
-    browser.disconnect()
+    await browser.disconnect()
   }
 }
 
-export async function create () {
-  return createBrowser()
+export async function getBrowserWSEndpoint () {
+  if (INSTANCE === undefined) {
+    INSTANCE = await createBrowser()
+    logger.info(`Chrome accepting connections on endpoint ${INSTANCE.wsEndpoint()}`)
+  }
+  return INSTANCE.wsEndpoint()
 }

Diff for: mermaid/src/index.js

@@ -5,13 +5,10 @@ import http from 'node:http'
 import micro from 'micro'
 import { SyntaxError, TimeoutError, Worker } from './worker.js'
 import Task from './task.js'
-import { create } from './browser-instance.js'
 
 (async () => {
   // QUESTION: should we create a pool of Chrome instances ?
-  const browser = await create()
-  logger.info(`Chrome accepting connections on endpoint ${browser.wsEndpoint()}`)
-  const worker = new Worker(browser)
+  const worker = new Worker()
   const server = new http.Server(
     micro.serve(async (req, res) => {
       // Add a /health route that renders a sample diagram by calling the worker

Diff for: mermaid/src/worker.js

@@ -4,6 +4,7 @@ import path from 'node:path'
 import puppeteer, { HTTPResponse, Page } from 'puppeteer'
 import { logger } from './logger.js'
 import { updateConfig } from './config.js'
+import { getBrowserWSEndpoint } from './browser-instance.js'
 
 const __dirname = fileURLToPath(new URL('.', import.meta.url))
 
@@ -22,8 +23,7 @@ export class SyntaxError extends Error {
 }
 
 export class Worker {
-  constructor (browserInstance) {
-    this.browserWSEndpoint = browserInstance.wsEndpoint()
+  constructor () {
     this.pageUrl = process.env.KROKI_MERMAID_PAGE_URL || `file://${path.join(__dirname, '..', 'assets', 'index.html')}`
     this.convertTimeout = process.env.KROKI_MERMAID_CONVERT_TIMEOUT || '10000'
   }
@@ -109,8 +109,9 @@ export class Worker {
    * @private
    */
   async _connect () {
+    const browserWSEndpoint = await getBrowserWSEndpoint()
     return await puppeteer.connect({
-      browserWSEndpoint: this.browserWSEndpoint,
+      browserWSEndpoint,
       ignoreHTTPSErrors: true
     })
   }