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xds: Fix ext_proc client hang on unary and server-streaming RPCs when upstream is not ready - #13147
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kannanjgithub merged 2 commits intoNov 6, 2026
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…when upstream is not ready Outbound request body messages in ExternalProcessorClientInterceptor were gated on super.isReady() before being forwarded to the upstream ClientCall. On unary and server-streaming RPCs (method.getType().clientSendsOneMessage()), ClientCallImpl intentionally suppresses onReady() notifications, meaning queued messages and halfClose were never drained when the upstream transport stream connected, causing the RPC to hang indefinitely. Treat the upstream call as ready for outbound message forwarding when method.getType().clientSendsOneMessage() is true via isUpstreamReady(). TAG=agy CONV=581f86a6-097d-44a2-9d6e-6f9d2e83cbc0
sauravzg
approved these changes
Nov 3, 2026
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| private boolean isUpstreamReady() { | ||
| return method.getType().clientSendsOneMessage() || super.isReady(); |
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This will result in isUpstreamReady returning true always for any unary or serverstreaming call. I'd expect this to return false after the call has been half closed.
It's less likely to matter because for these cases the call doesn't respect isReady anyways, but we should try to be semantically correct.
Ensure isUpstreamReady() returns false once the call has been half-closed upstream, maintaining semantic correctness for unary and server-streaming calls. TAG=agy CONV=581f86a6-097d-44a2-9d6e-6f9d2e83cbc0
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Outbound request body messages in
ExternalProcessorClientInterceptorwere gated onsuper.isReady()before being forwarded to the upstreamClientCall. On unary and server-streaming RPCs (method.getType().clientSendsOneMessage()),ClientCallImplintentionally suppressesonReady()notifications, meaning queued messages andhalfClosewere never drained when the upstream transport stream connected, causing the RPC to hang indefinitely.Treat the upstream call as ready for outbound message forwarding when
method.getType().clientSendsOneMessage()is true viaisUpstreamReady().Thanks @ran-su for reporting this.