Retry on failed download. (#12293)

packages/flutter_tools/lib/src/base/net.dart

@@ -4,39 +4,62 @@
 
 import 'dart:async';
 
+import '../base/context.dart';
 import '../globals.dart';
 import 'common.dart';
 import 'io.dart';
 
 const int kNetworkProblemExitCode = 50;
 
+typedef HttpClient HttpClientFactory();
+
 /// Download a file from the given URL and return the bytes.
 Future<List<int>> fetchUrl(Uri url) async {
-  printTrace('Downloading $url.');
+  int attempts = 0;
+  int duration = 1;
+  while (true) {
+    attempts += 1;
+    final List<int> result = await _attempt(url);
+    if (result != null)
+      return result;
+    printStatus('Download failed -- attempting retry $attempts in $duration second${ duration == 1 ? "" : "s"}...');
+    await new Future<Null>.delayed(new Duration(seconds: duration));
+    if (duration < 64)
+      duration *= 2;
+  }
+}
 
-  final HttpClient httpClient = new HttpClient();
+Future<List<int>> _attempt(Uri url) async {
+  printTrace('Downloading: $url');
+  HttpClient httpClient;
+  if (context[HttpClientFactory] != null) {
+    httpClient = context[HttpClientFactory]();
+  } else {
+    httpClient = new HttpClient();
+  }
   final HttpClientRequest request = await httpClient.getUrl(url);
   final HttpClientResponse response = await request.close();
-
-  printTrace('Received response statusCode=${response.statusCode}');
   if (response.statusCode != 200) {
-    throwToolExit(
-      'Download failed: $url\n'
-          '  because (${response.statusCode}) ${response.reasonPhrase}',
-      exitCode: kNetworkProblemExitCode,
-    );
+    if (response.statusCode > 0 && response.statusCode < 500) {
+      throwToolExit(
+        'Download failed.\n'
+        'URL: $url\n'
+        'Error: ${response.statusCode} ${response.reasonPhrase}',
+        exitCode: kNetworkProblemExitCode,
+      );
+    }
+    // 5xx errors are server errors and we can try again
+    printTrace('Download error: ${response.statusCode} ${response.reasonPhrase}');
+    return null;
   }
-
+  printTrace('Received response from server, collecting bytes...');
   try {
     final BytesBuilder responseBody = new BytesBuilder(copy: false);
     await for (List<int> chunk in response)
-        responseBody.add(chunk);
-
+      responseBody.add(chunk);
     return responseBody.takeBytes();
-  } on IOException catch (e) {
-    throw new ToolExit(
-      'Download failed: $url\n  $e',
-      exitCode: kNetworkProblemExitCode,
-    );
+  } on IOException catch (error) {
+    printTrace('Download error: $error');
+    return null;
   }
 }

packages/flutter_tools/test/base/net_test.dart

@@ -0,0 +1,115 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:flutter_tools/src/base/io.dart' as io;
+import 'package:flutter_tools/src/base/net.dart';
+import 'package:quiver/testing/async.dart';
+import 'package:test/test.dart';
+
+import '../src/context.dart';
+
+void main() {
+  testUsingContext('retry from 500', () async {
+    String error;
+    new FakeAsync().run((FakeAsync time) {
+      fetchUrl(Uri.parse('http://example.invalid/')).then((List<int> value) {
+        error = 'test completed unexpectedly';
+      }, onError: (dynamic error) {
+        error = 'test failed unexpectedly';
+      });
+      expect(testLogger.statusText, '');
+      time.elapse(const Duration(milliseconds: 10000));
+      expect(testLogger.statusText,
+        'Download failed -- attempting retry 1 in 1 second...\n'
+        'Download failed -- attempting retry 2 in 2 seconds...\n'
+        'Download failed -- attempting retry 3 in 4 seconds...\n'
+        'Download failed -- attempting retry 4 in 8 seconds...\n'
+      );
+    });
+    expect(testLogger.errorText, isEmpty);
+    expect(error, isNull);
+  }, overrides: <Type, Generator>{
+    HttpClientFactory: () => () => new MockHttpClient(500),
+  });
+
+  testUsingContext('retry from network error', () async {
+    String error;
+    new FakeAsync().run((FakeAsync time) {
+      fetchUrl(Uri.parse('http://example.invalid/')).then((List<int> value) {
+        error = 'test completed unexpectedly';
+      }, onError: (dynamic error) {
+        error = 'test failed unexpectedly';
+      });
+      expect(testLogger.statusText, '');
+      time.elapse(const Duration(milliseconds: 10000));
+      expect(testLogger.statusText,
+        'Download failed -- attempting retry 1 in 1 second...\n'
+        'Download failed -- attempting retry 2 in 2 seconds...\n'
+        'Download failed -- attempting retry 3 in 4 seconds...\n'
+        'Download failed -- attempting retry 4 in 8 seconds...\n'
+      );
+    });
+    expect(testLogger.errorText, isEmpty);
+    expect(error, isNull);
+  }, overrides: <Type, Generator>{
+    HttpClientFactory: () => () => new MockHttpClient(200),
+  });
+}
+
+class MockHttpClient implements io.HttpClient {
+  MockHttpClient(this.statusCode);
+
+  final int statusCode;
+
+  @override
+  Future<io.HttpClientRequest> getUrl(Uri url) async {
+    return new MockHttpClientRequest(statusCode);
+  }
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) {
+    throw 'io.HttpClient - $invocation';
+  }
+}
+
+class MockHttpClientRequest implements io.HttpClientRequest {
+  MockHttpClientRequest(this.statusCode);
+
+  final int statusCode;
+
+  @override
+  Future<io.HttpClientResponse> close() async {
+    return new MockHttpClientResponse(statusCode);
+  }
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) {
+    throw 'io.HttpClientRequest - $invocation';
+  }
+}
+
+class MockHttpClientResponse implements io.HttpClientResponse {
+  MockHttpClientResponse(this.statusCode);
+
+  @override
+  final int statusCode;
+
+  @override
+  String get reasonPhrase => '<reason phrase>';
+
+  @override
+  StreamSubscription<List<int>> listen(void onData(List<int> event), {
+    Function onError, void onDone(), bool cancelOnError
+  }) {
+    return new Stream<List<int>>.fromFuture(new Future<List<int>>.error(const io.SocketException('test')))
+      .listen(onData, onError: onError, onDone: onDone, cancelOnError: cancelOnError);
+  }
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) {
+    throw 'io.HttpClientResponse - $invocation';
+  }
+}

packages/flutter_tools/test/cache_test.dart

@@ -48,6 +48,7 @@ void main() {
       Platform: () => new FakePlatform()..environment = <String, String>{'FLUTTER_ALREADY_LOCKED': 'true'},
     });
   });
+
   group('Cache', () {
     test('should not be up to date, if some cached artifact is not', () {
       final CachedArtifact artifact1 = new MockCachedArtifact();

packages/flutter_tools/test/src/context.dart

@@ -60,7 +60,8 @@ void _defaultInitializeContext(AppContext testContext) {
     ..putIfAbsent(SimControl, () => new MockSimControl())
     ..putIfAbsent(Usage, () => new MockUsage())
     ..putIfAbsent(FlutterVersion, () => new MockFlutterVersion())
-    ..putIfAbsent(Clock, () => const Clock());
+    ..putIfAbsent(Clock, () => const Clock())
+    ..putIfAbsent(HttpClient, () => new MockHttpClient());
 }
 
 void testUsingContext(String description, dynamic testMethod(), {
@@ -244,3 +245,5 @@ class MockUsage implements Usage {
 class MockFlutterVersion extends Mock implements FlutterVersion {}
 
 class MockClock extends Mock implements Clock {}
+
+class MockHttpClient extends Mock implements HttpClient {}