feat(h2): honor maxRequestsPerClient - #5802
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`maxRequestsPerClient` was only honored over HTTP/1.1, so a `Client` with `allowH2: true` (or an `H2CClient`) kept a single session alive forever no matter how the option was configured. Count every stream that `session.request()` successfully opened against the limit, and retire the session once it is reached. A retired session is marked busy, so the dispatch loop stops putting new streams on it and queues them for the next connection instead. Retirement happens synchronously, before the write that reached the limit returns, so a resume pass dispatching several requests at once cannot overshoot. Tearing the session down is deferred until it has drained. Doing it in the same tick as `session.request()` makes nghttp2 refuse the very stream that triggered retirement, and a locally initiated `session.close()` can leave the socket half-open indefinitely when the peer keeps its side open. Drainage is tracked with a dedicated counter driven by each stream's physical `close` event rather than by `kOpenStreams`, which is released when the response completes and would therefore truncate a request body the server had already responded to. Closes nodejs#5787 Signed-off-by: John Lyon <264892913+johnlyonms@users.noreply.github.com>
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September 11, 2026 00:37
johnlyonms
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September 11, 2026 01:03
Use headersTimeout to reset retired HTTP/2 sessions whose accepted streams do not close, allowing queued requests to reconnect instead of stalling indefinitely. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Signed-off-by: John Lyon <264892913+johnlyonms@users.noreply.github.com>
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marked this pull request as ready for review
September 11, 2026 04:17
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| Over HTTP/1.1 a request is counted per message and the socket is reset once | ||
| the limit is reached. Over HTTP/2 a request is counted per successfully | ||
| opened stream: the session is retired once the limit is reached, meaning it | ||
| accepts no further streams. Streams it already accepted are allowed to | ||
| complete for up to `headersTimeout` before the connection is reset. Queued | ||
| and subsequent requests are then dispatched on a new session. |
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This can be a bit confusing for users, especially given that we have the maxConcurrentStreams; let's mention how they differ and how they interact with each other
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This relates to...
Closes #5787
Rationale
maxRequestsPerClientwas only honored by the HTTP/1.1 dispatcher. AClientcreated withallowH2: true, or anH2CClient, ignored the option and kept a single HTTP/2 session alive indefinitely. The option is important for rotatingconnections so load balancers can rebalance and clients do not remain pinned to one backend.
HTTP/2 also requires bounded retirement. Once a client has reached its request limit and we mark it as such, we must wait for existing streams to close. Waiting indefinitely for accepted streams to close lets a long-lived SSE, CONNECT, WebSocket, long-polling, gRPC, or stalled upload would block all queued work if we didn't implement a bound.
Changes
maxRequestsPerClient.headersTimeout. If accepted streams remain open at the deadline, reset the retired session with an informational error so queued requests remain replayable on a fresh connection.0,null, andundefineddisabled behavior.Client,H2CClient, and TypeScript consumers.The implementation tracks physical stream closure separately from
kOpenStreams. A response may finish while its request body is still uploading, so response completion alone is not sufficient to safely retire the session.Tests
test/http2-max-requests-per-client.jscontains 17 tests covering:1and disabled limitsClient,H2CClient, andPoolheadersTimeoutwhile queued work reconnects successfullyValidation:
Commits
12ac5172 feat(h2): honor maxRequestsPerClient41ba964e fix(h2): bound retired session drainingBreaking Changes and Deprecations
None. HTTP/1.1 behavior is unchanged. HTTP/2 users who do not configure
maxRequestsPerClient, or set it to0, see no change. SettingheadersTimeout: 0explicitly disables the retirement drain deadline.Status