Improve Gradle retry logic (#96554)

packages/flutter_tools/lib/src/android/gradle.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:math';
+
 import 'package:crypto/crypto.dart';
 import 'package:meta/meta.dart';
 import 'package:process/process.dart';
@@ -106,6 +108,9 @@ Iterable<String> _apkFilesFor(AndroidBuildInfo androidBuildInfo) {
   return <String>['app$flavorString-$buildType.apk'];
 }
 
+// The maximum time to wait before the tool retries a Gradle build.
+const Duration kMaxRetryTime = Duration(seconds: 10);
+
 /// An implementation of the [AndroidBuilder] that delegates to gradle.
 class AndroidGradleBuilder implements AndroidBuilder {
   AndroidGradleBuilder({
@@ -212,7 +217,7 @@ class AndroidGradleBuilder implements AndroidBuilder {
   /// * [target] is the target dart entry point. Typically, `lib/main.dart`.
   /// * If [isBuildingBundle] is `true`, then the output artifact is an `*.aab`,
   ///   otherwise the output artifact is an `*.apk`.
-  /// * [retries] is the max number of build retries in case one of the [GradleHandledError] handler
+  /// * [maxRetries] If not `null`, this is the max number of build retries in case a retry is triggered.
   Future<void> buildGradleApp({
     required FlutterProject project,
     required AndroidBuildInfo androidBuildInfo,
@@ -221,7 +226,8 @@ class AndroidGradleBuilder implements AndroidBuilder {
     required List<GradleHandledError> localGradleErrors,
     bool validateDeferredComponents = true,
     bool deferredComponentsEnabled = false,
-    int retries = 1,
+    int retry = 0,
+    @visibleForTesting int? maxRetries,
   }) async {
     assert(project != null);
     assert(androidBuildInfo != null);
@@ -401,7 +407,7 @@ class AndroidGradleBuilder implements AndroidBuilder {
           'Gradle task $assembleTask failed with exit code $exitCode',
           exitCode: exitCode,
         );
-      } else {
+      }
       final GradleBuildStatus status = await detectedGradleError!.handler(
         line: detectedGradleErrorLine!,
         project: project,
@@ -409,22 +415,29 @@ class AndroidGradleBuilder implements AndroidBuilder {
         multidexEnabled: androidBuildInfo.multidexEnabled,
       );
 
-        if (retries >= 1) {
+      if (maxRetries == null || retry < maxRetries) {
-          final String successEventLabel = 'gradle-${detectedGradleError!.eventLabel}-success';
         switch (status) {
           case GradleBuildStatus.retry:
+            // Use binary exponential backoff before retriggering the build.
+            // The expected wait times are: 100ms, 200ms, 400ms, and so on...
+            final int waitTime = min(pow(2, retry).toInt() * 100, kMaxRetryTime.inMicroseconds);
+            retry += 1;
+            _logger.printStatus('Retrying Gradle Build: #$retry, wait time: ${waitTime}ms');
+            await Future<void>.delayed(Duration(milliseconds: waitTime));
             await buildGradleApp(
               project: project,
               androidBuildInfo: androidBuildInfo,
               target: target,
               isBuildingBundle: isBuildingBundle,
               localGradleErrors: localGradleErrors,
-                retries: retries - 1,
+              retry: retry,
+              maxRetries: maxRetries,
             );
+            final String successEventLabel = 'gradle-${detectedGradleError!.eventLabel}-success';
             BuildEvent(successEventLabel, type: 'gradle', flutterUsage: _usage).send();
             return;
           case GradleBuildStatus.exit:
-            // noop.
+            // Continue and throw tool exit.
         }
       }
       BuildEvent('gradle-${detectedGradleError?.eventLabel}-failure', type: 'gradle', flutterUsage: _usage).send();
@@ -433,7 +446,6 @@ class AndroidGradleBuilder implements AndroidBuilder {
         exitCode: exitCode,
       );
     }
-    }
 
     if (isBuildingBundle) {
       final File bundleFile = findBundleFile(project, buildInfo, _logger, _usage);

packages/flutter_tools/lib/src/android/gradle_errors.dart

@@ -226,8 +226,8 @@ final GradleHandledError networkErrorHandler = GradleHandledError(
     required bool multidexEnabled,
   }) async {
     globals.printError(
-      '${globals.logger.terminal.warningMark} Gradle threw an error while downloading artifacts from the network. '
+      '${globals.logger.terminal.warningMark} '
-      'Retrying to download...'
+      'Gradle threw an error while downloading artifacts from the network.'
     );
     try {
       final String? homeDir = globals.platform.environment['HOME'];

packages/flutter_tools/test/general.shard/android/android_gradle_builder_test.dart

@@ -138,7 +138,8 @@ void main() {
         gradleUtils: FakeGradleUtils(),
         platform: FakePlatform(),
       );
-      processManager.addCommand(const FakeCommand(
+
+      const FakeCommand fakeCmd = FakeCommand(
         command: <String>[
           'gradlew',
           '-q',
@@ -151,23 +152,15 @@ void main() {
           'assembleRelease',
         ],
         exitCode: 1,
-        stderr: '\nSome gradle message\n'
+        stderr: '\nSome gradle message\n',
-      ));
+      );
-      processManager.addCommand(const FakeCommand(
+
-        command: <String>[
+      processManager.addCommand(fakeCmd);
-          'gradlew',
+
-          '-q',
+      const int maxRetries = 2;
-          '-Ptarget-platform=android-arm,android-arm64,android-x64',
+      for (int i = 0; i < maxRetries; i++) {
-          '-Ptarget=lib/main.dart',
+        processManager.addCommand(fakeCmd);
-          '-Pbase-application-name=io.flutter.app.FlutterApplication',
+      }
-          '-Pdart-obfuscation=false',
-          '-Ptrack-widget-creation=false',
-          '-Ptree-shake-icons=false',
-          'assembleRelease',
-        ],
-        exitCode: 1,
-        stderr: '\nSome gradle message\n'
-      ));
 
       fileSystem.directory('android')
         .childFile('build.gradle')
@@ -186,6 +179,7 @@ void main() {
       int testFnCalled = 0;
       await expectLater(() async {
        await builder.buildGradleApp(
+          maxRetries: maxRetries,
           project: FlutterProject.fromDirectoryTest(fileSystem.currentDirectory),
           androidBuildInfo: const AndroidBuildInfo(
             BuildInfo(
@@ -221,7 +215,10 @@ void main() {
         message: 'Gradle task assembleRelease failed with exit code 1'
       ));
 
-      expect(testFnCalled, equals(2));
+      expect(logger.statusText, contains('Retrying Gradle Build: #1, wait time: 100ms'));
+      expect(logger.statusText, contains('Retrying Gradle Build: #2, wait time: 200ms'));
+
+      expect(testFnCalled, equals(maxRetries + 1));
       expect(testUsage.events, contains(
         const TestUsageEvent(
           'build',

packages/flutter_tools/test/general.shard/android/gradle_errors_test.dart

@@ -103,7 +103,6 @@ at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:61)''';
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -134,7 +133,6 @@ at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:61)''';
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -156,7 +154,6 @@ Exception in thread "main" java.lang.RuntimeException: Timeout of 120000 reached
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -194,7 +191,6 @@ Exception in thread "main" javax.net.ssl.SSLHandshakeException: Remote host clos
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -224,7 +220,6 @@ Exception in thread "main" java.io.FileNotFoundException: https://downloads.grad
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -265,7 +260,6 @@ Exception in thread "main" java.net.SocketException: Connection reset
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -293,7 +287,6 @@ A problem occurred configuring root project 'android'.
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{
@@ -325,7 +318,6 @@ A problem occurred configuring root project 'android'.
       expect(testLogger.errorText,
         contains(
           'Gradle threw an error while downloading artifacts from the network.'
-          'Retrying to download...'
         )
       );
     }, overrides: <Type, Generator>{