net/http: should stop logging received GOAWAY

[jameshartig]

What version of Go are you using (go version)?

$ go version 1.15.3

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

N/A

What did you do?

We see a lot of logging:

http2: received GOAWAY [FrameHeader GOAWAY len=20], starting graceful shutdown

without any indication of what to do or how to fix that. It seems like @bradfitz said we should just remove this log #18776 (comment) but it got lost in removing the other logs.

If we want to keep this log around, we should at least fix the message to include the ErrCode since just printing the frame header is useless.

What did you expect to see?

I expect to not see these logs if there's nothing the application can do to prevent them or if there's something actionable to do, then I expect to see the relevant error code to decide what to do.

What did you see instead?

Instead, I see these log messages over 7,000 times an hour.

[cagedmantis]

/cc @bradfitz @empijei

[empijei]

Sounds like a bug to me, and indeed the linked discussion seems to suggest we should have removed those long time ago.

Looking at the code there seem to be already some logic to conditionally log these:

go/src/net/http/h2_bundle.go

Lines 5290 to 5297 in 1095dd6

	func (sc *http2serverConn) processGoAway(f *http2GoAwayFrame) error {
	sc.serveG.check()
	if f.ErrCode != http2ErrCodeNo {
	sc.logf("http2: received GOAWAY %+v, starting graceful shutdown", f)
	} else {
	sc.vlogf("http2: received GOAWAY %+v, starting graceful shutdown", f)
	}
	sc.startGracefulShutdownInternal()

So we should either change the first message to include the error or just default to call vlogf.

Since this doesn't seem like a particularly useful message unless stuff is being run in debug mode I would be in favor of the latter.

I don't have a strong opinion on either solutions but I'd be happy to prepare a CL to do either.

@jameshartig @bradfitz WDYT?