pjfanning opened a new pull request, #921:
URL: https://github.com/apache/pekko-grpc/pull/921
### Motivation
With the pekko-http client backend, cancelling a server streaming call (e.g.
`client.itKeepsReplying(req).runWith(Sink.head)`) never reached the server.
`responseToSource` always added `CancellationBarrierGraphStage`, which keeps
reading the response so the trailers can be read. As a result the server stream
kept running and was never stopped.
### Modification
Port of akka/akka-grpc#1832 (Akka gRPC 2.4.0, Apache 2.0 since its change
date, 2026-10-24):
- `PekkoHttpClientUtils.responseToSource` takes a `streamingResponse` flag
(default `false`) and adds the cancellation barrier only for single responses.
- The pekko-http `InternalChannel` passes the flag it already gets for each
call.
Unlike upstream, the flag goes after the existing `maxInboundMessageSize`
parameter and has a default, so existing callers don't change.
`responseToSource` is `@InternalApi`, and the existing 2.0.x MiMa exclude
already covers it.
`interop-tests/.../PekkoHttpClientCancelSpec.scala` is copied from
upstream's `plugin-tester-scala/.../AkkaHttpClientCancelSpec.scala`. It keeps
the original Lightbend copyright line, with the ASF "derived from Akka" header
above it as in neighbouring files. It is adapted to Pekko as follows:
- It lives in `interop-tests`, so it runs in the sbt build.
- It uses the classic `TestKit`/`TestProbe`.
- It calls `watchTermination` without the empty parameter list, which is
Pekko's signature.
- It selects the backend with `withBackend("pekko-http")`.
### Result
Cancelling a server streaming call with the pekko-http backend now stops the
stream on the server.
### Tests
- New `PekkoHttpClientCancelSpec`: fails without the fix (the server stream
did not complete within 5 seconds), passes with it
- `sbt runtime/test`: 189 passed
- `sbt interop-tests/test`: 255 passed
- `sbt runtime/mimaReportBinaryIssues`: passed
- `scalafmt --mode diff-ref=upstream/main` run
- `sbt interop-tests/Test/headerCheck`: passed
### References
Refs akka/akka-grpc#1832
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