reverseproxy: prevent body close on dial-error retries#7547
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francislavoie merged 1 commit intocaddyserver:masterfrom Mar 4, 2026
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) cloneRequest shallow-copies Body, so clonedReq.Body and r.Body share the same io.ReadCloser. When Go's transport hits a dial error it calls req.Body.Close() before reading any bytes, which kills the original body for all subsequent retry attempts ("http: invalid Read on closed Body" → 502). Wrap the body in io.NopCloser when retries are configured so the transport's Close is a no-op. The real body is closed by the HTTP server when the handler returns. For already-buffered bodies (via request_buffers) the buffer is extracted into the same NopCloser path so both cases share a single code block. Unlike full eager buffering this adds zero memory or latency overhead — streaming is preserved and only the Close call is intercepted.
francislavoie
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Yeah, that makes a lot of sense. Didn't realize dials would close the body, that's surprising, but to be expected I suppose.
Thanks!
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Props go to @jafowler for interrogating the AI long enough to identify and repro the issue. |
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Fixes #7546
cloneRequest shallow-copies Body, so clonedReq.Body and r.Body share the same io.ReadCloser. When Go's transport hits a dial error it calls req.Body.Close() before reading any bytes, which kills the original body for all subsequent retry attempts ("http: invalid Read on closed Body" → 502).
Wrap the body in io.NopCloser when retries are configured so the transport's Close is a no-op. The real body is closed by the HTTP server when the handler returns. For already-buffered bodies (via request_buffers) the buffer is extracted into the same NopCloser path so both cases share a single code block.
Assistance Disclosure
AI debugged the issue. I wrote the code, and AI generated the tests & commit message.