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Brad Fitzpatrick authored
If I put a 10 millisecond sleep at testHookWaitResLoop, before the big select in (*persistConn).roundTrip, two flakes immediately started happening, TestTransportBodyReadError (#19231) and TestTransportPersistConnReadLoopEOF. The problem was that there are many ways for a RoundTrip call to fail (errors reading from Request.Body while writing the response, errors writing the response, errors reading the response due to server closes, errors due to servers sending malformed responses, cancelations, timeouts, etc.), and many of those failures then tear down the TCP connection, causing more failures, since there are always at least three goroutines involved (reading, writing, RoundTripping). Because the errors were communicated over buffered channels to a giant select, the error returned to the caller was a function of which random select case was called, which was why a 10ms delay before the select brought out so many bugs. (several fixed in my previous CLs the past few days). Instead, track the error explicitly in the transportRequest, guarded by a mutex. In addition, this CL now: * differentiates between the two ways writing a request can fail: the io.Copy reading from the Request.Body or the io.Copy writing to the network. A new io.Reader type notes read errors from the Request.Body. The read-from-body vs write-to-network errors are now prioritized differently. * unifies the two mapRoundTripErrorFromXXX methods into one mapRoundTripError method since their logic is now the same. * adds a (*Request).WithT(*testing.T) method in export_test.go, usable by tests, to call t.Logf at points during RoundTrip. This is disabled behind a constant except when debugging. * documents and deflakes TestClientRedirectContext I've tested this CL with high -count values, with/without -race, with/without delays before the select, etc. So far it seems robust. Fixes #19231 (TestTransportBodyReadError flake) Updates #14203 (source of errors unclear; they're now tracked more) Updates #15935 (document Transport errors more; at least understood more now) Change-Id: I3cccc3607f369724b5344763e35ad2b7ea415738 Reviewed-on: https://go-review.googlesource.com/37495 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by:
Josh Bleecher Snyder <josharian@gmail.com>
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