feature(proxy): Adds special handling for client cancellations in proxy error handler #1522
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…xy error handler Silences logging for client cancellations during polling to reduce noise in logs. Client-side cancellations are common during long-running operations and should not be treated as errors.
Summary of ChangesHello @soilSpoon, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request refines the proxy's error handling mechanism to differentiate between genuine upstream errors and client-initiated cancellations. By explicitly ignoring context.Canceled errors, the system's logs will become cleaner and more focused on actionable issues, improving operational clarity. Highlights
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Code Review
This pull request aims to reduce log noise by silencing errors from client cancellations in the proxy. The change correctly identifies context.Canceled errors but has a flaw: by simply returning from the error handler, the client receives an incorrect 200 OK status. My review provides a correction to use errors.Is for robust error checking and to explicitly send a 499 Client Closed Request status, aligning the code with the comment's intent and preventing incorrect client responses.
| if err == context.Canceled { | ||
| return | ||
| } |
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There are two issues with the current implementation for handling client cancellations:
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Incorrect HTTP Status: Simply returning from the
ErrorHandlerwill cause theginframework to send a200 OKresponse with an empty body if no response has been written yet. This is misleading for the client. The code comment correctly suggests returning a499status, which indicates a client-side cancellation. The code should be updated to write this status code. -
Error Checking: The check
err == context.Canceledis not robust enough. The error returned by the HTTP transport when a request is canceled is often a wrapped error (e.g.,*url.Error). Usingerrors.Is(err, context.Canceled)is the correct way to check for cancellation errors.
Please also ensure the errors package is imported to use errors.Is.
| if err == context.Canceled { | |
| return | |
| } | |
| if errors.Is(err, context.Canceled) { | |
| rw.WriteHeader(gin.StatusClientClosedRequest) | |
| return | |
| } |
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Pull request overview
Reduces log noise in the Amp upstream reverse proxy by adding special-case handling in the proxy error handler for client-initiated request cancellations (common during long-polling).
Changes:
- Adds a cancellation check in
proxy.ErrorHandlerto skip error logging when the request is canceled. - Imports
contextto enable cancellation detection.
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| if err == context.Canceled { | ||
| return |
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err == context.Canceled is brittle here because proxy/transport errors are commonly wrapped (e.g., *url.Error), so cancellations may still get logged. Prefer errors.Is(err, context.Canceled) (and/or checking req.Context().Err()) to reliably detect client cancellations.
| proxy.ErrorHandler = func(rw http.ResponseWriter, req *http.Request, err error) { | ||
| // Client-side cancellations are common during polling; return 499 without logging | ||
| if err == context.Canceled { | ||
| return | ||
| } |
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This change introduces special-case behavior for canceled requests; there are existing proxy tests in proxy_test.go (including TestReverseProxy_ErrorHandler), but no assertion covering the cancellation path. Adding a focused test for the cancellation case would prevent regressions and clarify the intended status/response behavior.
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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@copilot open a new pull request to apply changes based on the comments in this thread |
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Silences logging for client cancellations during polling to reduce noise in logs.
Client-side cancellations are common during long-running operations and should not be treated as errors.