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perf(mobile): use HTTP/2 on Android through app-wide Cronet engines (#9435)

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Follows #8897 (iOS HTTP/2), now on main.

## What

Android gets the same app-wide shared sessions as iOS, backed by Cronet
(`cronet_http`) instead of `NSURLSession`:

- One Cronet engine per traffic class (API, media), so requests to a
host multiplex over one HTTP/2 connection and gzip is inflated natively,
off the Dart isolate.
- HTTP/2 on, HTTP cache off, QUIC off. QUIC would be a separate behavior
change, and `cronet_http`'s changelog lists DNS failures with QUIC on
cellular.
- Streamed uploads (media and voice notes) stay on `dart:io` on Android:
`CronetClient` reads a request body into memory before sending it, which
would break upload progress and copy large attachments in full.
- If no Cronet provider is available (no Google Play services), the
engine fails to build and the app keeps `dart:io`, as today.
- Transport error classification covers Cronet failures alongside
`NSURLSession` ones, so invite and pairing errors keep their friendly
messages.

## Measurements

Android emulator (API 36, arm64), profile builds of this branch and
main, signed in to the Feedback community. 8 cold starts per build,
alternating builds in blocks of 4. Times are for relay `/query` requests
started in the first 8 s.

| | main (`dart:io`) | this branch (Cronet) |
|---|---|---|
| First query response | 6.99 s | 1.99 s |
| Startup burst settled | 8.36 s | 2.78 s |
| Burst after the first connection | 1.44 s | 0.77 s |
| Query latency after the first connection, median / p90 | 165 / 1567 ms
| 106 / 158 ms |

**Unexplained stall:** most of main's startup gap is a ~5 s stall before
its first response on every cold start. Its cause is unconfirmed; my
guess is `dart:io` loading its CA store on the emulator, which HTTP/2
itself wouldn't fix, so the first two rows likely overstate the win on
real devices. The rows after the first connection exclude the stall and
are the fairer comparison. I also tried emulated EDGE throttling, but
the emulator's throttle did not slow its traffic, so there are no
slow-link numbers yet.

## Regressions

None found. Devices without Play services keep `dart:io`. Cleartext
`http://` requests keep the handle's own `dart:io` client, as on iOS.

## Testing

- Full mobile suite passes (`flutter test`, 4784 tests).
- Automated app run on the emulator: onboarding, Feedback nsec import,
channel and DM list load, and 16 cold starts with request timing. Media
loading wasn't separately exercised.
- No visible UI change, so no screenshots.

---------

Signed-off-by: Tom Brow <tomb@squareup.com>
Co-authored-by: Tom Brow <tomb@squareup.com>
This commit is contained in:
Tom Brow
2026-11-13 13:33:58 -08:00
committed by GitHub
parent 36fa0fe318
commit d1a8c3607d
8 changed files with 191 additions and 43 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
mobile/lib/features/channels/channels_page/badges.dart
View File

@@ -47,7 +47,7 @@ class _ErrorView extends HookConsumerWidget {
return 'Server error (${error.statusCode}). Try again later.';
}
if (error is SocketException ||
urlSessionFailure(error) == TransportFailure.unreachable) {
transportFailure(error) == TransportFailure.unreachable) {
return 'Could not reach the relay server.';
}
return 'Something went wrong. Check your connection.';

10
mobile/lib/features/invites/invite_join_provider.dart
View File

@@ -516,14 +516,14 @@ String _friendlyInviteError(Object error) {
if (message.contains('join_policy_required')) {
return 'Review this community’s join requirements in your browser, then return to Buzz.';
}
final transportFailure = urlSessionFailure(error);
if (transportFailure == TransportFailure.insecure) {
final failure = transportFailure(error);
if (failure == TransportFailure.insecure) {
return 'Secure connection failed. Check your network settings and try again.';
}
if (transportFailure == TransportFailure.timedOut) {
if (failure == TransportFailure.timedOut) {
return 'Connection timed out. Check your internet connection and try again.';
}
if (transportFailure == TransportFailure.unreachable ||
if (failure == TransportFailure.unreachable ||
message.contains('SocketException') ||
message.contains('Connection refused') ||
message.contains('Network is unreachable') ||
@@ -535,7 +535,7 @@ String _friendlyInviteError(Object error) {
String _friendlyStarterSetupError(Object error) {
final message = error.toString();
if (urlSessionFailure(error) == TransportFailure.unreachable ||
if (transportFailure(error) == TransportFailure.unreachable ||
message.contains('SocketException') ||
message.contains('Connection refused') ||
message.contains('Network is unreachable') ||

8
mobile/lib/features/pairing/pairing_provider_helpers.dart
View File

@@ -2,8 +2,8 @@ part of 'pairing_provider.dart';
String _friendlyErrorMessage(Object error) {
final message = error.toString();
final transportFailure = urlSessionFailure(error);
if (transportFailure == TransportFailure.unreachable ||
final failure = transportFailure(error);
if (failure == TransportFailure.unreachable ||
message.contains('SocketException') ||
message.contains('Connection refused') ||
message.contains('Network is unreachable') ||
@@ -20,13 +20,13 @@ String _friendlyErrorMessage(Object error) {
message.contains('Null check operator used on a null value')) {
return 'Pairing stopped because of an internal error. Please try again.';
}
if (transportFailure == TransportFailure.insecure ||
if (failure == TransportFailure.insecure ||
message.contains('HandshakeException') ||
message.contains('CERTIFICATE_VERIFY_FAILED')) {
return 'Secure connection failed. Check your network settings '
'and try again.';
}
if (transportFailure == TransportFailure.timedOut ||
if (failure == TransportFailure.timedOut ||
message.contains('TimeoutException') ||
message.contains('timed out')) {
return 'Connection timed out. Check your internet connection and '

120
mobile/lib/shared/http/app_http_client.dart
View File

@@ -1,10 +1,12 @@
import 'dart:async';
import 'dart:io' show Platform;
import 'package:cronet_http/cronet_http.dart';
import 'package:cupertino_http/cupertino_http.dart';
import 'package:http/http.dart' as http;
import 'package:jni/jni.dart' show JThrowable;
import 'package:objective_c/objective_c.dart';
import 'package:flutter/foundation.dart' show visibleForTesting;
import 'package:flutter/foundation.dart' show debugPrint, visibleForTesting;
/// Which app-wide connection pool a request belongs to.
enum HttpTraffic {
@@ -15,20 +17,34 @@ enum HttpTraffic {
media,
}
final _sessions = <HttpTraffic, http.Client>{};
/// The app-wide session for each traffic class, or null where the platform
/// has none.
final _sessions = <HttpTraffic, http.Client?>{};
/// An HTTP client for [traffic]. Callers own it and close it as usual.
///
/// On iOS, every client for the same [traffic] shares one `NSURLSession`, so
/// requests to a host multiplex over one HTTP/2 connection instead of opening
/// an HTTP/1.1 connection each, and gzip is inflated natively, off the Dart
/// isolate. Media has its own session, and so its own connection, so image
/// bytes cannot starve queries queued behind them on a shared connection.
/// On iOS and Android, every client for the same [traffic] shares one native
/// session (`NSURLSession` or a Cronet engine), so requests to a host
/// multiplex over one HTTP/2 connection instead of opening an HTTP/1.1
/// connection each, and gzip is inflated natively, off the Dart isolate.
/// Media has its own session, and so its own connection, so image bytes
/// cannot starve queries queued behind them on a shared connection.
///
/// Elsewhere this is `http.Client()`, which also honors `http.runWithClient`.
http.Client newAppHttpClient([HttpTraffic traffic = HttpTraffic.api]) {
if (!Platform.isIOS) return http.Client();
return SharedSessionClient(_sessions[traffic] ??= _openUrlSession());
final session = _sessions.putIfAbsent(traffic, _openNativeSession);
if (session == null) return http.Client();
return SharedSessionClient(session, streamsUploads: !Platform.isAndroid);
}
/// Whether [newAppHttpClient] uses a native session on this device.
bool get hasNativeHttpSession =>
_sessions.putIfAbsent(HttpTraffic.api, _openNativeSession) != null;
http.Client? _openNativeSession() {
if (Platform.isIOS) return _openUrlSession();
if (Platform.isAndroid) return _openCronetSession();
return null;
}
/// Matches the `dart:io` transport apart from the protocol: no HTTP cache and
@@ -42,22 +58,55 @@ http.Client _openUrlSession() {
return CupertinoClient.fromSessionConfiguration(config);
}
/// Matches the `dart:io` transport apart from the protocol: no HTTP cache,
/// and Cronet keeps no cookies. QUIC stays off, so this changes only the
/// HTTP version.
///
/// Null when no Cronet provider is available: Cronet comes from Google Play
/// services, which some Android devices don't have. Those keep `dart:io`.
http.Client? _openCronetSession() {
final CronetEngine engine;
try {
engine = CronetEngine.build(
cacheMode: CacheMode.disabled,
enableHttp2: true,
enableQuic: false,
);
} on JThrowable catch (error) {
debugPrint('Cronet is unavailable, using dart:io: ${error.message}');
return null;
}
return CronetClient.fromCronetEngine(engine);
}
/// A caller's handle on an app-wide session. Like closing a `dart:io` client,
/// [close] cancels the handle's requests still in flight and refuses later
/// ones, but leaves the session open for other handles. Closing a
/// `CupertinoClient` while any of its requests run would also throw.
/// `CupertinoClient` while any of its requests run would also throw, and
/// closing a `CronetClient` would stop the shared engine.
///
/// App Transport Security blocks cleartext `URLSession` loads from public
/// hosts, while saved community icons and remote media may still use
/// `http://`. Those keep the handle's own `dart:io` client, as before.
///
/// Unless [streamsUploads], a streamed request with a body (media and voice
/// note uploads) also keeps `dart:io`: `CronetClient` reads the whole body
/// into memory before sending it, so progress would reach 100% before any
/// byte left and a large attachment would be copied in full.
@visibleForTesting
class SharedSessionClient extends http.BaseClient {
SharedSessionClient(this._session, {http.Client Function()? cleartext})
: _newCleartext = cleartext ?? http.Client.new;
SharedSessionClient(
this._session, {
http.Client Function()? cleartext,
this.streamsUploads = true,
}) : _newCleartext = cleartext ?? http.Client.new;
final http.Client _session;
final http.Client Function() _newCleartext;
/// Whether the session streams request bodies instead of buffering them.
final bool streamsUploads;
/// One abort trigger per request still running, so [close] can cancel it.
/// A request leaves the set once its response body is done, failed or
/// cancelled, or once the caller's own abort trigger fires. A body nobody
@@ -75,7 +124,8 @@ class SharedSessionClient extends http.BaseClient {
request.url,
);
}
if (request.url.scheme != 'https') {
if (request.url.scheme != 'https' ||
(!streamsUploads && _isStreamedUpload(request))) {
return (_cleartext ??= _newCleartext()).send(request);
}
final abort = Completer<void>();
@@ -130,6 +180,11 @@ class SharedSessionClient extends http.BaseClient {
);
}
static bool _isStreamedUpload(http.BaseRequest request) =>
request is! http.Request &&
request.method != 'GET' &&
request.method != 'HEAD';
/// A copy of [request] that the session cancels when [trigger] completes.
http.BaseRequest _withAbortTrigger(
http.BaseRequest request,
@@ -178,17 +233,20 @@ class SharedSessionClient extends http.BaseClient {
}
}
/// How an iOS transport request failed, for user-facing messages. `dart:io`
/// failures are recognized by their messages instead.
/// How a native transport request failed, for user-facing messages.
/// `dart:io` failures are recognized by their messages instead.
enum TransportFailure { unreachable, insecure, timedOut }
/// The [TransportFailure] for a `URLSession` error, or null for any other
/// error.
TransportFailure? urlSessionFailure(Object error) {
if (error is! NSErrorClientException) return null;
if (error.error.domain.toDartString() != 'NSURLErrorDomain') return null;
return urlErrorFailure(error.error.code);
}
/// The [TransportFailure] for a `URLSession` or Cronet error, or null for
/// any other error.
TransportFailure? transportFailure(Object error) => switch (error) {
NSErrorClientException(:final error)
when error.domain.toDartString() == 'NSURLErrorDomain' =>
urlErrorFailure(error.code),
NetworkException(:final errorCode, :final cronetInternalErrorCode) =>
cronetErrorFailure(errorCode, cronetInternalErrorCode),
_ => null,
};
/// Classifies an `NSURLErrorDomain` code.
@visibleForTesting
@@ -207,3 +265,21 @@ TransportFailure? urlErrorFailure(int code) => switch (code) {
>= -1206 && <= -1200 => TransportFailure.insecure,
_ => null,
};
/// Classifies a Cronet `NetworkException` by its `ERROR_*` code and, for
/// `ERROR_OTHER`, Chromium's internal net error code.
@visibleForTesting
TransportFailure? cronetErrorFailure(int errorCode, int internalCode) =>
switch (errorCode) {
4 || 6 => TransportFailure.timedOut,
// Host not resolved, offline, network changed, connection closed,
// refused or reset, address unreachable.
1 || 2 || 3 || 5 || 7 || 8 || 9 => TransportFailure.unreachable,
// SSL protocol error, cipher mismatch, and the certificate errors.
11
when internalCode == -107 ||
internalCode == -113 ||
(internalCode <= -200 && internalCode >= -299) =>
TransportFailure.insecure,
_ => null,
};

9
mobile/lib/shared/relay/relay_http_query_client.dart
View File

@@ -5,15 +5,16 @@ import 'package:http/http.dart' as http;
import 'package:http/io_client.dart';
import 'package:buzz/shared/http/app_http_client.dart';
/// The default transport. On iOS, the app-wide `NSURLSession` inflates gzip
/// natively, off the Dart isolate. `dart:io` would inflate on the calling
/// isolate, so leave its responses compressed for the response decoder.
/// The default transport. On iOS and Android, the app-wide native session
/// inflates gzip natively, off the Dart isolate. `dart:io` would inflate on
/// the calling isolate, so leave its responses compressed for the response
/// decoder.
///
/// A non-`dart:io` client supplied through `http.runWithClient`, such as a
/// `MockClient`, is used as is. An `IOClient` is replaced, not closed, since
/// it may be shared.
http.Client _defaultTransport() {
if (Platform.isIOS) return newAppHttpClient();
if (hasNativeHttpSession) return newAppHttpClient();
final client = http.Client();
if (client is! IOClient) return client;
return IOClient(HttpClient()..autoUncompress = false);

22
mobile/pubspec.lock
View File

@@ -288,6 +288,14 @@ packages:
url: "https://pub.dev"
source: hosted
version: "1.15.0"
cronet_http:
dependency: "direct main"
description:
name: cronet_http
sha256: "7f8976ce1531399e42b4c5ad0937bd57bd93fbcff564f7d51c695be19850e977"
url: "https://pub.dev"
source: hosted
version: "1.10.1"
cross_file:
dependency: transitive
description:
@@ -808,13 +816,13 @@ packages:
source: hosted
version: "1.0.5"
jni:
dependency: transitive
dependency: "direct main"
description:
name: jni
sha256: c2230682d5bc2362c1c9e8d3c7f406d9cbba23ab3f2e203a025dd47e0fb2e68f
sha256: "2e91e6087291affd10b31b6c872f3e3ac7dc5d93b51b5ba485d930c8f08bde6c"
url: "https://pub.dev"
source: hosted
version: "1.0.0"
version: "1.1.2"
jni_flutter:
dependency: transitive
description:
@@ -823,6 +831,14 @@ packages:
url: "https://pub.dev"
source: hosted
version: "1.0.1"
jni_util:
dependency: transitive
description:
name: jni_util
sha256: "1ba86da04a5f2bf18fde2edb235587e70c5b0fc5bd4ba955f46b00942c3fc35f"
url: "https://pub.dev"
source: hosted
version: "1.0.0"
json_annotation:
dependency: transitive
description:

6
mobile/pubspec.yaml
View File

@@ -18,9 +18,11 @@ dependencies:
hooks_riverpod: ^3.0.3
flutter_hooks: ^0.21.3
http: ^1.4.0
# iOS HTTP transport (NSURLSession): HTTP/2 and native gzip. See
# lib/shared/http/app_http_client.dart.
# Native HTTP transports, NSURLSession on iOS and Cronet on Android: HTTP/2
# and native gzip. See lib/shared/http/app_http_client.dart.
cronet_http: ^1.10.1
cupertino_http: ^3.1.0
jni: ^1.1.0
objective_c: ^9.5.0
crypto: ^3.0.7
flutter_secure_storage: ^10.0.0

57
mobile/test/shared/http/app_http_client_test.dart
View File

@@ -8,7 +8,7 @@ import 'package:http/http.dart' as http;
import 'package:http/testing.dart';
void main() {
test('off iOS, clients come from http.Client()', () {
test('without a native session, clients come from http.Client()', () {
final mock = MockClient((_) async => http.Response('', 200));
for (final traffic in HttpTraffic.values) {
expect(
@@ -213,6 +213,47 @@ void main() {
expect(cleartextClosed, isTrue);
});
test(
'streamed uploads keep dart:io when the session buffers bodies',
() async {
final sessionRequests = <String>[];
final fallbackRequests = <String>[];
final client = SharedSessionClient(
MockClient.streaming((request, body) async {
await body.drain<void>();
sessionRequests.add('${request.method} ${request.url.path}');
return http.StreamedResponse(const Stream.empty(), 200);
}),
cleartext: () => MockClient.streaming((request, body) async {
await body.drain<void>();
fallbackRequests.add('${request.method} ${request.url.path}');
return http.StreamedResponse(const Stream.empty(), 200);
}),
streamsUploads: false,
);
final upload = http.StreamedRequest(
'PUT',
Uri.parse('https://media.example/upload'),
);
upload.sink
..add([1, 2, 3])
..close();
await client.send(upload);
final download = http.StreamedRequest(
'GET',
Uri.parse('https://media.example/video'),
);
unawaited(download.sink.close());
await client.send(download);
await client.post(Uri.parse('https://relay.example/query'), body: '{}');
client.close();
expect(fallbackRequests, ['PUT /upload']);
expect(sessionRequests, ['GET /video', 'POST /query']);
},
);
test('URLSession error codes map to user-facing failure kinds', () {
expect(urlErrorFailure(-1009), TransportFailure.unreachable);
expect(urlErrorFailure(-1004), TransportFailure.unreachable);
@@ -220,7 +261,19 @@ void main() {
expect(urlErrorFailure(-1200), TransportFailure.insecure);
expect(urlErrorFailure(-1202), TransportFailure.insecure);
expect(urlErrorFailure(-999), isNull);
expect(urlSessionFailure(http.ClientException('offline')), isNull);
expect(transportFailure(http.ClientException('offline')), isNull);
});
test('Cronet error codes map to user-facing failure kinds', () {
expect(cronetErrorFailure(4, -7), TransportFailure.timedOut);
expect(cronetErrorFailure(6, -118), TransportFailure.timedOut);
expect(cronetErrorFailure(1, -105), TransportFailure.unreachable);
expect(cronetErrorFailure(2, -106), TransportFailure.unreachable);
expect(cronetErrorFailure(7, -102), TransportFailure.unreachable);
expect(cronetErrorFailure(11, -202), TransportFailure.insecure);
expect(cronetErrorFailure(11, -107), TransportFailure.insecure);
expect(cronetErrorFailure(11, -324), isNull);
expect(cronetErrorFailure(10, -356), isNull);
});
}