Unbork unfurler concurrency implementation

unfurler/src/concurrency/ReusablePage.ts

@@ -1,5 +1,5 @@
 import * as puppeteer from 'puppeteer';
-import ConcurrencyImplementation, { ResourceData } from 'puppeteer-cluster/dist/concurrency/ConcurrencyImplementation';
+import ConcurrencyImplementation from 'puppeteer-cluster/dist/concurrency/ConcurrencyImplementation';
 import { timeoutExecute } from 'puppeteer-cluster/dist/util';
 
 import config from '../config';
@@ -8,17 +8,24 @@ const mempoolHost = config.MEMPOOL.HTTP_HOST + (config.MEMPOOL.HTTP_PORT ? ':' +
 const BROWSER_TIMEOUT = 8000;
 // maximum lifetime of a single page session
 const maxAgeMs = (config.PUPPETEER.MAX_PAGE_AGE || (24 * 60 * 60)) * 1000;
+const maxConcurrency = config.PUPPETEER.CLUSTER_SIZE;
 
-interface repairablePage extends puppeteer.Page {
+interface RepairablePage extends puppeteer.Page {
   repairRequested?: boolean;
   language?: string | null;
+  createdAt?: number;
+  free?: boolean;
+  index?: number;
+}
+
+interface ResourceData {
+  page: RepairablePage;
 }
 
 export default class ReusablePage extends ConcurrencyImplementation {
 
   protected browser: puppeteer.Browser | null = null;
-  protected currentPage: repairablePage | null = null;
-  protected pageCreatedAt: number = 0;
+  protected pages: RepairablePage[] = [];
   private repairing: boolean = false;
   private repairRequested: boolean = false;
   private openInstances: number = 0;
@@ -46,40 +53,70 @@ export default class ReusablePage extends ConcurrencyImplementation {
     }
 
     try {
-      this.browser = await this.puppeteer.launch(this.options) as puppeteer.Browser;
+      await this.init();
     } catch (err) {
       throw new Error('Unable to restart chrome.');
     }
-    this.currentPage = null;
     this.repairRequested = false;
     this.repairing = false;
     this.waitingForRepairResolvers.forEach(resolve => resolve());
     this.waitingForRepairResolvers = [];
-    await this.createResources();
   }
 
   public async init() {
     this.browser = await this.puppeteer.launch(this.options);
+    const promises = []
+    for (let i = 0; i < maxConcurrency; i++) {
+      const newPage = await this.initPage();
+      newPage.index = this.pages.length;
+      console.log('initialized page ', newPage.index);
+      this.pages.push(newPage);
+    }
   }
 
   public async close() {
     await (this.browser as puppeteer.Browser).close();
   }
 
+  protected async initPage(): Promise<RepairablePage> {
+    const page = await (this.browser as puppeteer.Browser).newPage() as RepairablePage;
+    page.language = null;
+    page.createdAt = Date.now();
+    const defaultUrl = mempoolHost + '/preview/block/1';
+    page.on('pageerror', (err) => {
+      page.repairRequested = true;
+    });
+    await page.goto(defaultUrl, { waitUntil: "load" });
+    page.free = true;
+    return page
+  }
+
   protected async createResources(): Promise<ResourceData> {
-    if (!this.currentPage) {
-      this.currentPage = await (this.browser as puppeteer.Browser).newPage();
-      this.currentPage.language = null;
-      this.pageCreatedAt = Date.now();
-      const defaultUrl = mempoolHost + '/preview/block/1';
-      this.currentPage.on('pageerror', (err) => {
-        this.repairRequested = true;
-      });
-      await this.currentPage.goto(defaultUrl, { waitUntil: "load" });
+    const page = this.pages.find(p => p.free);
+    if (!page) {
+      console.log('no free pages!')
+      throw new Error('no pages available');
+    } else {
+      page.free = false;
+      return { page };
     }
-    return {
-      page: this.currentPage
+  }
+
+  protected async repairPage(page) {
+    // create a new page
+    const newPage = await this.initPage();
+    newPage.free = true;
+    // replace the old page
+    newPage.index = page.index;
+    this.pages.splice(page.index, 1, newPage);
+    // clean up the old page
+    try {
+      await page.goto('about:blank', {timeout: 200}); // prevents memory leak (maybe?)
+    } catch (e) {
+      console.log('unexpected page repair error');
     }
+    await page.close();
+    return newPage;
   }
 
   public async workerInstance() {
@@ -97,8 +134,15 @@ export default class ReusablePage extends ConcurrencyImplementation {
 
           close: async () => {
             this.openInstances -= 1; // decrement first in case of error
+            if (resources?.page != null) {
+              if (resources.page.repairRequested || (Date.now() - (resources.page.createdAt || 0) > maxAgeMs)) {
+                resources.page = await this.repairPage(resources.page);
+              } else {
+                resources.page.free = true;
+              }
+            }
 
-            if (this.repairRequested || this.currentPage?.repairRequested || (Date.now() - this.pageCreatedAt > maxAgeMs)) {
+            if (this.repairRequested) {
               await this.repair();
             }
           },
@@ -108,9 +152,7 @@ export default class ReusablePage extends ConcurrencyImplementation {
       close: async () => {},
 
       repair: async () => {
-        console.log('Repair requested');
-        this.repairRequested = true;
-        await this.repair();
+        await this.repairPage(resources.page);
       },
     };
   }

unfurler/src/index.ts

@@ -51,8 +51,6 @@ class Server {
     this.server.listen(config.SERVER.HTTP_PORT, () => {
       console.log(`Mempool Unfurl Server is running on port ${config.SERVER.HTTP_PORT}`);
     });
-
-    this.initClusterPages();
   }
 
   async stopServer() {
@@ -70,16 +68,7 @@ class Server {
     this.app.get('*', (req, res) => { return this.renderHTML(req, res) })
   }
 
-  async initClusterPages() {
-    for (let i = 0; i < config.PUPPETEER.CLUSTER_SIZE; i++) {
-      this.cluster?.execute({ action: 'init' });
-    }
-  }
-
   async clusterTask({ page, data: { url, path, action } }) {
-    if (action === 'init') {
-      return;
-    }
     try {
       const urlParts = parseLanguageUrl(path);
       if (page.language !== urlParts.lang) {