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feat(http2): add a pooled, multiplexed HTTP/2 http.Client - #1956

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feat(http2): add a pooled, multiplexed HTTP/2 http.Client#1956
brianquinlan merged 38 commits into
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@demolaf

@demolaf demolaf commented Jul 30, 2026 •
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Closes #1385

Adds Http2Client, a pooled, multiplexed http.Client backed by HTTP/2 connections, plus the ClientPool it's built on — fixes dart:io's HttpClient opening one connection per concurrent request. Ported and generalized from a downstream implementation built for firebase/firebase-admin-dart#305.

  • ClientPool: most-full-first packing, idle GC, failure retirement, and a lease API so a slot can outlive the call that claimed it
  • Http2Client: pools per host:port, caps concurrent handshakes globally, multi-host safe (e.g. as googleapis_auth's baseClient)
  • Never opens more concurrent streams on a connection than the server's SETTINGS_MAX_CONCURRENT_STREAMS allows, and doesn't use a connection at all until that frame has arrived — see Http2Client.settingsTimeout
  • A request holds its pool slot until the response body ends or is cancelled, so the pool's view matches the number of streams actually open
  • Retries once when a pooled connection was closed by the peer before reuse
  • Adds ClientTransportConnection.peerMaxConcurrentStreams. This is a new member on an implementable class, hence the minor version bump

@demolaf
demolaf marked this pull request as draft July 30, 2026 09:43
@demolaf demolaf mentioned this pull request Jul 30, 2026
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demolaf marked this pull request as ready for review July 30, 2026 13:14
mosuem
mosuem reviewed Aug 3, 2026
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Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/test/http2_client_test.dart Resolved
brianquinlan
brianquinlan reviewed Aug 3, 2026
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I'll have more review feedback tomorrow. Also, this PR adds (preliminary) conformance tests: #1960

You might want to add them to this PR.

Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
demolaf added 15 commits August 4, 2026 10:17
@demolaf
docs(http2): ClientPool.size is used by production code, not just tests
059cf76
@demolaf
refactor(http2): use collection's .sum instead of manual fold sums
84c0d66
@demolaf
style(http2): use braces for single-statement ifs in _sendOverHttp2
0ca6c5c
@demolaf
style(http2): use a case pattern for _maybeCompleteDrain's null check
3279971
@demolaf
test(http2): drop redundant comment on self-signed test cert bypass
659e447
@demolaf
feat(http2): expose peer's SETTINGS_MAX_CONCURRENT_STREAMS via peerMa…
33631c7 
…xConcurrentStreams
@demolaf
test(http2): add client conformance tests for Http2Client
168d1e9
@demolaf
fix(http2): cap streams per connection by the server's advertised limit
832cae0
@demolaf
fix(http2): correct response translation and error types in Http2Client
d8d0ba7
@demolaf
fix(http2): make ClientPool.terminate idempotent and snapshot-safe
a47fe1b
@demolaf
fix(http2): don't couple an operation to its resource's teardown
bf3dfb4
@demolaf
feat(http2): give ClientPool an explicit lease API
5e0b38d
@demolaf
fix(http2): hold a pool slot until the response body completes
0ae4a17
@demolaf
fix(http2): don't multiplex onto a connection whose stream limit is u…
a1fef44 
…nknown
@demolaf
docs(http2): record the pooling behaviour changes and known isOpen race
92987b6
@demolaf
demolaf force-pushed the pooled-http2-client branch from e8b8590 to 39b75f9 Compare August 6, 2026 14:08
@demolaf

demolaf commented Aug 6, 2026

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@brianquinlan @mosuem I'm deferring the TODOs in the conformance tests to a later PR since this is already quite a lot, sounds good?

brianquinlan
brianquinlan reviewed Aug 6, 2026
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Comment thread pkgs/http2/example/main.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/connection.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
@demolaf
demolaf force-pushed the pooled-http2-client branch from 90b0813 to af53e7f Compare August 14, 2026 17:25
@demolaf
demolaf force-pushed the pooled-http2-client branch from a5cea15 to a05fb28 Compare August 14, 2026 18:30
@demolaf
demolaf requested review from brianquinlan and mosuem August 18, 2026 10:17
brianquinlan
brianquinlan reviewed Aug 19, 2026
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Comment thread pkgs/http2/example/main.dart Resolved
Comment thread pkgs/http2/lib/src/client_pool.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
Comment thread pkgs/http2/lib/src/http2_client.dart Resolved
brianquinlan
brianquinlan reviewed Aug 21, 2026
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Comment thread pkgs/http2/README.md Resolved
@brianquinlan
brianquinlan merged commit 6543145 into dart-lang:master Aug 24, 2026
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@bl4ckswordsman bl4ckswordsman mentioned this pull request Aug 26, 2026
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copybara-service Bot pushed a commit to dart-lang/sdk that referenced this pull request Sep 11, 2026
@natebosch dart-scoped@luci-project-accounts.iam.gserviceaccount.com
[deps] rev core, dartdoc, ecosystem, http, i18n, native, shelf, tools…
5e99c28 
…, web, webdriver

Revisions updated by `dart tools/rev_sdk_deps.dart`.

core (https://github.com/dart-lang/core/compare/773de9d..7e8caaf):
  7e8caafa  Thu Sep 10 12:51:06 2026 +0200  Jonas Finnemann Jensen  Fix doc comment in FixedDateTimeFormatter (dart-lang/core#998)
  0fbe0cc3  Thu Sep 3 16:26:19 2026 -0700  Nate Bosch  Mark Context and Style as final (dart-lang/core#995)
  1f563bb2  Tue Sep 1 21:54:29 2026 +0000  dependabot[bot]  Bump the github-actions group with 5 updates (dart-lang/core#996)
  b80e4885  Fri Aug 28 12:18:12 2026 +0200  Lasse R.H. Nielsen  Release package:platform 3.2 (dart-lang/core#994)
  9727aadc  Wed Aug 26 09:34:02 2026 -0700  Nate Bosch  Add new lints (dart-lang/core#989)

dartdoc (https://github.com/dart-lang/dartdoc/compare/2737669..df2f2cd):
  df2f2cde  Tue Sep 8 11:09:41 2026 +0200  dependabot[bot]  Bump analyzer_testing from 0.3.4 to 0.4.1 (dart-lang/dartdoc#4282)
  b028f551  Tue Sep 1 18:56:04 2026 +0000  dependabot[bot]  Bump the github-actions group with 2 updates (dart-lang/dartdoc#4281)

ecosystem (https://github.com/dart-lang/ecosystem/compare/cda8bd5..1bdafd8):
  1bdafd8  Wed Sep 2 16:31:27 2026 -0700  Nate Bosch  Tighten workflow for posting PR comments (dart-lang/ecosystem#451)
  fc3dd9a  Mon Aug 31 11:38:33 2026 -0700  Kevin Moore  fix(firehose): update existing publishing PR comments when no packages are ready to publish (dart-lang/ecosystem#449)
  e0a78b4  Mon Aug 31 11:12:56 2026 -0700  Kevin Moore  fix(firehose): bump dependency_validator pinned hash to 5.0.6 (dart-lang/ecosystem#450)
  60fca9f  Tue Aug 25 16:31:57 2026 -0700  Kevin Moore  Condense firehose package publishing table in PR validation (dart-lang/ecosystem#445)
  b79f68c  Mon Aug 24 05:47:23 2026 -0700  Kevin Moore  chore(health): remove 3rd-party coveralls action dependency (dart-lang/ecosystem#446)

http (https://github.com/dart-lang/http/compare/a9176ac..066e158):
  066e158  Wed Sep 9 17:15:24 2026 +0200  Eve Chen  Skip chunked framing when contentLength is null (dart-lang/http#1970)
  a6145c3  Wed Sep 9 09:26:05 2026 +1000  Liam Appelbe  [cupertino_http] Migrate to FFIgen 22 (dart-lang/http#1986)
  92b20d1  Fri Sep 4 10:29:18 2026 -0700  Brian Quinlan  test(conformance): HEAD with content-length set (dart-lang/http#1979)
  bb553a6  Fri Sep 4 11:40:41 2026 +1000  Liam Appelbe  [cronet_http] Migrate to JNIgen v1 and use the Dart config API (dart-lang/http#1980)
  deacd15  Thu Sep 3 16:09:07 2026 -0700  Brian Quinlan  chore(cupertino_http): ready to release 3.1.0 (dart-lang/http#1985)
  ace65bc  Wed Sep 2 17:01:14 2026 -0700  Brian Quinlan  ci(cupertino_http): only run iOS tests when run-ios-tests label is present (dart-lang/http#1984)
  7a79b45  Wed Sep 2 17:00:49 2026 -0700  Brian Quinlan  ci(cupertino_http): enable caching for Flutter SDK and pub dependencies (dart-lang/http#1982)
  8dbb44c  Wed Sep 2 17:00:19 2026 -0700  Brian Quinlan  chore(cupertino_http): migrate ios_test from CocoaPods to Swift Package Manager (dart-lang/http#1983)
  b815a06  Wed Sep 2 23:55:13 2026 +0200  stwime  [cupertino_http] Regenerate bindings with ffigen 21 (dart-lang/http#1975)
  0d5bee4  Wed Sep 2 10:50:41 2026 -0700  dependabot[bot]  chore(deps): bump the github-actions group across 1 directory with 10 updates (dart-lang/http#1976)
  6543145  Mon Aug 24 16:32:07 2026 +0100  Ademola Fadumo  feat(http2): add a pooled, multiplexed HTTP/2 http.Client (dart-lang/http#1956)
  a0d49cb  Wed Aug 19 18:22:11 2026 -0700  Brian Quinlan  fix(http2): reject server push when disabled (dart-lang/http#1966)
  8007c92  Wed Aug 19 17:57:46 2026 -0700  Brian Quinlan  fix(http2): reject requests that exceed `SETTINGS_MAX_CONCURRENT_STREAMS` (dart-lang/http#1965)
  1827980  Wed Aug 19 17:06:20 2026 -0700  dart-ecosystem-bot[bot]  Tidy: package:cupertino_http (dart-lang/http#1968)
  a24ab46  Wed Aug 19 17:03:03 2026 -0700  Brian Quinlan  chore: upgrade to jnigen 0.17.0 (dart-lang/http#1964)
  9fa7266  Tue Aug 18 16:35:25 2026 -0700  Kevin Moore  chore: harden GitHub Actions workflows against Zizmor findings (dart-lang/http#1971)

i18n (https://github.com/dart-lang/i18n/compare/2fd9412..1f5ea2f):
  1f5ea2fb  Tue Sep 8 13:12:25 2026 +0200  Moritz  [intl4x] Add intl4x.brittle_i18n_testing environment define (dart-lang/i18n#1093)

native (https://github.com/dart-lang/native/compare/38fe179..84d7eda):
  84d7edac0  Wed Sep 9 07:38:19 2026 +0200  Jakob Kordež  [ffigen] Resolve unexposed C++ types through their canonical type (dart-lang/native#3608)
  7b77c03a9  Wed Sep 9 10:31:06 2026 +0530  Sivapriya  [jnigen] Add javadoc.io fallback for missing Javadoc (dart-lang/native#3586)
  520d280d1  Wed Sep 9 06:57:16 2026 +0200  Jakob Kordež  [ffigen] Treat class declarations like structs, decide C++ class binding by POD-ness (dart-lang/native#3607)
  350ed4541  Tue Sep 8 09:55:21 2026 +1000  Liam Appelbe  [ffigen] Prepare to publish (dart-lang/native#3620)
  2cb086a2f  Mon Sep 7 12:15:34 2026 +1000  Liam Appelbe  [ffigen] Migrate remaining FFIgen YAML configs (dart-lang/native#3614)
  dc2937e7c  Mon Sep 7 11:07:46 2026 +1000  Liam Appelbe  [ffigen] Symbol file imports (dart-lang/native#3617)
  c69575ce5  Fri Sep 4 04:05:59 2026 +0200  Jakob Kordež  [ffigen] Skip C++ methods with unbindable return types (dart-lang/native#3591)
  5d6f82d9d  Fri Sep 4 08:41:35 2026 +1000  Liam Appelbe  [objective_c] Migrate ffigen yaml configs (dart-lang/native#3615)
  ef6db8652  Fri Sep 4 08:41:20 2026 +1000  Liam Appelbe  [ffigen] Migrate test YAML configs (dart-lang/native#3613)
  9f3dae7e6  Fri Sep 4 08:38:55 2026 +1000  Liam Appelbe  [ffigen] Migrate FFIgen configs across the repo (dart-lang/native#3616)
  895977bca  Fri Sep 4 08:37:25 2026 +1000  Liam Appelbe  [jnigen] Prepare to publish v1.0.0 (dart-lang/native#3612)
  03f1d8e29  Thu Sep 3 09:13:56 2026 +1000  Liam Appelbe  [ffigen] Config cleanup (dart-lang/native#3606)
  9560e6c8a  Wed Sep 2 09:58:51 2026 +1000  Liam Appelbe  [jnigen] Migrate YAMLs to Dart (dart-lang/native#3600)
  8836b56ed  Tue Sep 1 05:35:52 2026 +0000  dependabot[bot]  [infra] Bump the github-actions group with 7 updates (dart-lang/native#3604)
  3041c6e88  Tue Sep 1 09:06:17 2026 +1000  Liam Appelbe  [jnigen] Little bits of cleanup (dart-lang/native#3599)
  c4af7b839  Tue Sep 1 09:01:03 2026 +1000  Liam Appelbe  [jni_flutter] Bump kotlin version (dart-lang/native#3598)
  ff508aeb2  Thu Aug 27 12:30:15 2026 +0200  Daco Harkes  [code_assets] [native_toolchain_c] Add arm64e (dart-lang/native#3589)
  f914da89c  Thu Aug 27 05:37:06 2026 +0200  Jakob Kordež  [ffigen] Fix infinite recursion when parsing cyclic C++ class references (dart-lang/native#3584)
  0f05f8895  Thu Aug 27 11:36:48 2026 +1000  Liam Appelbe  [ffigen][jnigen] Clean up dartdoc categories (dart-lang/native#3587)
  ae80f0dfa  Wed Aug 26 18:23:47 2026 +0200  Alexander Thomas  Merge pull request `#3588` from dart-lang/merge-cherry-pick-3581
  bcf1529b9  Wed Aug 26 07:51:49 2026 -0700  Brian Quinlan  Merge branch 'main' into merge-cherry-pick-3581
  bd5e0ff05  Wed Aug 26 14:24:50 2026 +1000  Liam Appelbe  [ffigen] Final config cleanup (dart-lang/native#3575)
  363e9ae91  Tue Aug 25 14:35:54 2026 -0700  Brian Quinlan  Merge remote-tracking branch 'origin/cherry-pick-3581' into merge-cherry-pick-3581
  d51c53334  Tue Aug 25 01:07:51 2026 -0700  Brian Quinlan  [hooks_runner] use target path separator (dart-lang/native#3581)
  7ee7629d6  Tue Aug 25 13:59:24 2026 +0530  Varad Raj Agrawal  [native_toolchain_c] Inject FileSystem for file system access (dart-lang/native#3555)

shelf (https://github.com/dart-lang/shelf/compare/fb3f931..f36dd68):
  f36dd68  Tue Sep 1 12:29:24 2026 +0000  dependabot[bot]  build(deps): bump dart-lang/setup-dart in the github-actions group (dart-lang/shelf#539)
  3dbf65b  Thu Aug 27 16:05:14 2026 -0700  Kevin Moore  fix(shelf_static): Handle int overflow during byte range parsing (dart-lang/shelf#538)

tools (https://github.com/dart-lang/tools/compare/441ff29..682f285):
  682f2854  Thu Sep 10 09:08:32 2026 -0700  Keerti Parthasarathy  [unified_analytics] Update code to mock `isExternal` in tests. (dart-lang/tools#2594)
  b09f9a33  Fri Sep 4 11:46:08 2026 -0700  Kevin Moore  [api_summary] Support dart:js_interop annotations (@js and @JSExport) (dart-lang/tools#2527)
  292130b6  Thu Sep 3 19:27:26 2026 -0700  Kevin Moore  [api_summary] Introduce ApiFacet model and migrate package:meta annotations (dart-lang/tools#2526)
  cacb5a56  Wed Sep 2 10:03:40 2026 +0700  herdiyanitdev  fix(markdown): avoid quadratic parse time on long unbroken words (dart-lang/tools#2536)
  10ea88d0  Tue Sep 1 10:08:46 2026 -0700  Nate Bosch  Remove @internal annotations for now (dart-lang/tools#2576)
  3306952a  Tue Sep 1 06:11:16 2026 +0000  dependabot[bot]  build(deps): bump the github-actions group with 4 updates (dart-lang/tools#2577)
  94ee86ed  Fri Aug 28 14:54:46 2026 -0700  Kevin Moore  feat: export ErrorListener and ErrorCollector from yaml.dart (dart-lang/tools#2551)
  c7f7a63f  Fri Aug 28 12:25:32 2026 -0700  Nate Bosch  Prepare to publish packages (dart-lang/tools#2562)
  3b3b22c2  Fri Aug 28 09:10:36 2026 +0200  Jonas Finnemann Jensen  [extension_discovery] Fixup review comments (dart-lang/tools#2557)

web (https://github.com/dart-lang/web/compare/6b84f81..e5c6c02):
  e5c6c02  Tue Sep 1 06:54:56 2026 +0000  dependabot[bot]  Bump the github-actions group with 2 updates (dart-lang/web#574)
  c4d8884  Thu Aug 20 21:31:53 2026 +0000  dependabot[bot]  Bump the github-actions group with 3 updates (dart-lang/web#569)
  6d96d9e  Thu Aug 20 14:08:47 2026 -0700  Kevin Moore  chore: harden GitHub Actions workflows against Zizmor findings (dart-lang/web#568)

webdriver (https://github.com/google/webdriver.dart/compare/3a711eb..9b2e87d):
  9b2e87d  Wed Sep 9 12:55:07 2026 -0700  Kevin Moore  ci: align publish workflow and enable direct PR comments (google/webdriver.dart#348)
  1da600f  Fri Sep 4 11:40:38 2026 -0700  dependabot[bot]  Bump the actions group across 1 directory with 3 updates (google/webdriver.dart#347)
  0046657  Fri Sep 4 13:10:07 2026 -0400  Nate Biggs  Publish version 3.2.0 (google/webdriver.dart#346)


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Change-Id: Ib3be7bf3d3a0c91ebeb01002b7e63fcb86de1f92
TAG=agy
CONV=e6fd1c32-ded3-443f-83e5-2e15b4ffaccb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/544260
Commit-Queue: Johnni Winther <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>
Auto-Submit: Nate Bosch <[email protected]>
@meoyawn meoyawn mentioned this pull request Oct 31, 2026
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Add a http.Client compatible client

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