fix: skip empty output buffers to avoid empty HTTP/2 DATA frames#115
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take_output returns an empty buffer when there is nothing to send but the output stream is not closed (e.g. while replaying already-completed entries on resume-after-suspend). The SDK forwarded this empty buffer to the response channel unconditionally, emitting one empty HTTP/2 DATA frame per replayed await. Proxies such as Envoy terminate connections with more than one consecutive empty-payload frame, so suspended invocations never resumed. Guard the three send sites (async_result_poll, select_poll, consume_to_end) to skip empty buffers. The EOF arm is unchanged, so a closed output still maps to UnexpectedOutputClosed. Fixes restatedev#114 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
slinkydeveloper
approved these changes
Jun 8, 2026
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take_output returns an empty buffer when there is nothing to send but the output stream is not closed (e.g. while replaying already-completed entries on resume-after-suspend). The SDK forwarded this empty buffer to the response channel unconditionally, emitting one empty HTTP/2 DATA frame per replayed await. Proxies such as Envoy terminate connections with more than one consecutive empty-payload frame, so suspended invocations never resumed.
Guard the three send sites (async_result_poll, select_poll, consume_to_end) to skip empty buffers. The EOF arm is unchanged, so a closed output still maps to UnexpectedOutputClosed.
Fixes #114