From 609e7d08085badd112a1429af464436c8d4b1434 Mon Sep 17 00:00:00 2001
From: OpenClawd <openclawd@cloonar.com>
Date: Tue, 24 Feb 2026 07:51:05 +0000
Subject: [PATCH] fix: hot-swap browser restart to prevent QUEUE_FULL with
 single browser

Root cause: With BROWSER_COUNT=1, the hourly browser restart set
restarting=true, drained all pages, closed the browser, THEN launched
a new one. During that window (seconds), all requests queued and
timed out after 30s with QUEUE_FULL errors.

Fix: Launch the new browser BEFORE closing the old one (hot-swap).
This ensures zero downtime during browser recycling, even with a
single browser instance.
---
 src/services/browser.ts | 45 ++++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/src/services/browser.ts b/src/services/browser.ts
index 9e30d92..33d04ea 100644
--- a/src/services/browser.ts
+++ b/src/services/browser.ts
@@ -99,9 +99,21 @@ export function releasePage(page: Page, inst: BrowserInstance): void {
 async function scheduleRestart(inst: BrowserInstance): Promise<void> {
   if (inst.restarting) return;
   inst.restarting = true;
-  logger.info(`Scheduling browser ${inst.id} restart`);
+  logger.info(`Scheduling browser ${inst.id} restart (hot-swap)`);
 
-  // Wait for pages to drain (max 30s)
+  // Launch new browser FIRST so we never have zero capacity
+  const newBrowser = await puppeteer.launch({
+    headless: true,
+    executablePath: process.env.PUPPETEER_EXECUTABLE_PATH || undefined,
+    args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-gpu", "--disable-dev-shm-usage",
+           "--disable-background-networking", "--disable-default-apps", "--disable-extensions",
+           "--disable-sync", "--disable-translate", "--metrics-recording-only",
+           "--no-first-run", "--safebrowsing-disable-auto-update"],
+  });
+  const newPages = await createPages(newBrowser, PAGES_PER_BROWSER);
+
+  // Wait for in-flight pages to drain (max 30s)
+  const oldBrowser = inst.browser;
   await Promise.race([
     new Promise<void>(resolve => {
       const check = () => {
@@ -113,23 +125,24 @@ async function scheduleRestart(inst: BrowserInstance): Promise<void> {
     new Promise<void>(r => setTimeout(r, 30000)),
   ]);
 
-  for (const page of inst.availablePages) await page.close().catch(() => {});
-  inst.availablePages.length = 0;
-  try { await inst.browser.close(); } catch {}
-
-  inst.browser = await puppeteer.launch({
-    headless: true,
-    executablePath: process.env.PUPPETEER_EXECUTABLE_PATH || undefined,
-    args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-gpu", "--disable-dev-shm-usage",
-           "--disable-background-networking", "--disable-default-apps", "--disable-extensions",
-           "--disable-sync", "--disable-translate", "--metrics-recording-only",
-           "--no-first-run", "--safebrowsing-disable-auto-update"],
-  });
-  inst.availablePages.push(...await createPages(inst.browser, PAGES_PER_BROWSER));
+  // Swap: install new browser and pages, then clean up old
+  const oldPages = inst.availablePages.splice(0);
+  inst.browser = newBrowser;
+  inst.availablePages.push(...newPages);
   inst.jobCount = 0;
   inst.lastRestartTime = Date.now();
   inst.restarting = false;
-  logger.info(`Browser ${inst.id} restarted`);
+  logger.info(`Browser ${inst.id} restarted (hot-swap complete)`);
+
+  // Clean up old browser in background
+  for (const page of oldPages) await page.close().catch(() => {});
+  try { await oldBrowser.close(); } catch {}
+
+  // Drain any waiters now that pages are available
+  while (waitingQueue.length > 0 && inst.availablePages.length > 0) {
+    const waiter = waitingQueue.shift()!;
+    waiter.resolve({ page: inst.availablePages.pop()!, instance: inst });
+  }
 }
 
 export async function initBrowser(): Promise<void> {