From ad540e4f3f2665e5fe2b73ce1f04db3d666643db Mon Sep 17 00:00:00 2001
From: Jonah Williams <jonahwilliams@google.com>
Date: Wed, 23 Jun 2021 19:26:02 -0700
Subject: [PATCH] [flutter_tools] retry chrome launch up to 3 times (#85162)

---
 .../flutter_tools/lib/src/web/chrome.dart     | 25 ++++---
 .../test/general.shard/web/chrome_test.dart   | 65 +++++++++++++++----
 2 files changed, 69 insertions(+), 21 deletions(-)

diff --git a/packages/flutter_tools/lib/src/web/chrome.dart b/packages/flutter_tools/lib/src/web/chrome.dart
index a3a252e67f..70181b07f8 100644
--- a/packages/flutter_tools/lib/src/web/chrome.dart
+++ b/packages/flutter_tools/lib/src/web/chrome.dart
@@ -249,7 +249,9 @@ class ChromiumLauncher {
 
     // Keep attempting to launch the browser until one of:
     // - Chrome launched successfully, in which case we just return from the loop.
-    // - The tool detected an unretriable Chrome error, in which case we throw ToolExit.
+    // - The tool reached the maximum retry count, in which case we throw ToolExit.
+    const int kMaxRetries = 3;
+    int retry = 0;
     while (true) {
       final Process process = await _processManager.start(args);
 
@@ -263,6 +265,7 @@ class ChromiumLauncher {
       // Wait until the DevTools are listening before trying to connect. This is
       // only required for flutter_test --platform=chrome and not flutter run.
       bool hitGlibcBug = false;
+      bool shouldRetry = false;
       await process.stderr
         .transform(utf8.decoder)
         .transform(const LineSplitter())
@@ -270,6 +273,7 @@ class ChromiumLauncher {
           _logger.printTrace('[CHROME]:$line');
           if (line.contains(_kGlibcError)) {
             hitGlibcBug = true;
+            shouldRetry = true;
           }
           return line;
         })
@@ -282,17 +286,22 @@ class ChromiumLauncher {
             // Return value unused.
             return '';
           }
-          _logger.printTrace('Failed to launch browser. Command used to launch it: ${args.join(' ')}');
-          throw ToolExit(
-            'Failed to launch browser. Make sure you are using an up-to-date '
-            'Chrome or Edge. Otherwise, consider using -d web-server instead '
-            'and filing an issue at https://github.com/flutter/flutter/issues.',
-          );
+          if (retry >= kMaxRetries) {
+            _logger.printTrace('Failed to launch browser after $kMaxRetries tries. Command used to launch it: ${args.join(' ')}');
+            throw ToolExit(
+              'Failed to launch browser. Make sure you are using an up-to-date '
+              'Chrome or Edge. Otherwise, consider using -d web-server instead '
+              'and filing an issue at https://github.com/flutter/flutter/issues.',
+            );
+          }
+          shouldRetry = true;
+          return '';
         });
 
-      if (!hitGlibcBug) {
+      if (!hitGlibcBug && !shouldRetry) {
         return process;
       }
+      retry += 1;
 
       // A precaution that avoids accumulating browser processes, in case the
       // glibc bug doesn't cause the browser to quit and we keep looping and
diff --git a/packages/flutter_tools/test/general.shard/web/chrome_test.dart b/packages/flutter_tools/test/general.shard/web/chrome_test.dart
index b52f87e8e5..fa1af031fe 100644
--- a/packages/flutter_tools/test/general.shard/web/chrome_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/chrome_test.dart
@@ -461,22 +461,61 @@ void main() {
     );
   });
 
-  testWithoutContext('gives up retrying when a non-glibc error happens', () async {
+  testWithoutContext('can retry launch when chrome fails to start', () async {
+    const List<String> args = <String>[
+      'example_chrome',
+      '--user-data-dir=/.tmp_rand0/flutter_tools_chrome_device.rand0',
+      '--remote-debugging-port=12345',
+      ...kChromeArgs,
+      '--headless',
+      '--disable-gpu',
+      '--no-sandbox',
+      '--window-size=2400,1800',
+      'example_url',
+    ];
+
+    // Pretend to random error 3 times.
+    for (int i = 0; i < 3; i++) {
+      processManager.addCommand(const FakeCommand(
+        command: args,
+        stderr: 'BLAH BLAH',
+      ));
+    }
+
+    // Succeed on the 4th try.
     processManager.addCommand(const FakeCommand(
-      command: <String>[
-        'example_chrome',
-        '--user-data-dir=/.tmp_rand0/flutter_tools_chrome_device.rand0',
-        '--remote-debugging-port=12345',
-        ...kChromeArgs,
-        '--headless',
-        '--disable-gpu',
-        '--no-sandbox',
-        '--window-size=2400,1800',
-        'example_url',
-      ],
-      stderr: 'nothing in the std error indicating glibc error',
+      command: args,
+      stderr: kDevtoolsStderr,
     ));
 
+    expect(
+      () async => chromeLauncher.launch(
+        'example_url',
+        skipCheck: true,
+        headless: true,
+      ),
+      returnsNormally,
+    );
+  });
+
+  testWithoutContext('gives up retrying when an error happens more than 3 times', () async {
+    for (int i = 0; i < 4; i++) {
+      processManager.addCommand(const FakeCommand(
+        command: <String>[
+          'example_chrome',
+          '--user-data-dir=/.tmp_rand0/flutter_tools_chrome_device.rand0',
+          '--remote-debugging-port=12345',
+          ...kChromeArgs,
+          '--headless',
+          '--disable-gpu',
+          '--no-sandbox',
+          '--window-size=2400,1800',
+          'example_url',
+        ],
+        stderr: 'nothing in the std error indicating glibc error',
+      ));
+    }
+
     expect(
       () async => chromeLauncher.launch(
         'example_url',