Propagate cancellation through HTTP/2 output - #250
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The `ensure` block in `passthrough` attempts to close the stream with
`self.close_write(error)`, but there are two issues:
- For a cancelled task, `error` will be `nil` since it won't get set by
the `rescue => error` block, as `Async::Cancel` isn't a `StandardError`
- More seriously, the actual `write()` can block indefinitely, stalling
reactor shutdown
This led to backtraces like this during Falcon worker shutdown, forcing
Falcon to `SIGKILL` the worker process after the timeout:
async-2.45.1 async/scheduler.rb:382 IO::Event::Selector::URing#io_write
async-2.45.1 async/scheduler.rb:382 Async::Scheduler#io_write
io-stream-0.11 io/stream/buffered.rb:112 IO#write
io-stream-0.11 io/stream/buffered.rb:112 IO::Stream::Buffered#syswrite
io-stream-0.11 io/stream/writable.rb:99 IO::Stream::Writable#drain
io-stream-0.11 io/stream/writable.rb:47 block in IO::Stream::Writable#flush
io-stream-0.11 io/stream/writable.rb:46 Thread::Mutex#synchronize
io-stream-0.11 io/stream/writable.rb:46 IO::Stream::Writable#flush
protocol-http2 protocol/http2/framer.rb:58 Protocol::HTTP2::Framer#flush
protocol-http2 protocol/http2/connection.rb:253 Protocol::HTTP2::Connection#write_frame
protocol-http2 protocol/http2/stream.rb:115 Protocol::HTTP2::Stream#write_frame
protocol-http2 protocol/http2/stream.rb:203 Protocol::HTTP2::Stream#write_data
protocol-http2 protocol/http2/stream.rb:213 Protocol::HTTP2::Stream#send_data
async-http-0.94.2 http2/stream.rb:140 Async::HTTP::Protocol::HTTP2::Stream#finish_output
async-http-0.94.2 http2/output.rb:68 Async::HTTP::Protocol::HTTP2::Output#close_write
async-http-0.94.2 http2/output.rb:120 Async::HTTP::Protocol::HTTP2::Output#passthrough
async-2.45.1 async/task.rb:225 block in Async::Task#run
async-2.45.1 async/task.rb:523 block in Async::Task#schedule
Fix this with `rescue Exception => error`, and add a 1-second timeout
around `close_write` if `error` is non-`nil`.
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Signed-off-by: Samuel Williams <samuel.williams@shopify.com> Assisted-By: devx/2fb5639b-d636-44ad-a666-9088d8c41cc1
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The
ensureblock inOutput#passthroughcallsclose_write(error), but a cancelled task previously lefterrorasnil: a barerescue => errorcatchesStandardError, whileAsync::Cancelinherits directly fromException.As a result, cancellation was presented to
finish_outputas orderly completion. Explicitly rescueAsync::CancelalongsideStandardError, preserving the cancellation object for body and stream cleanup before re-raising it.This change intentionally does not add timeout or forced transport-abort policy. It only corrects cancellation propagation.
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