Go: net/http: make default configs have better timeouts

[rsc]

See https://github.com/golang/go/issues/23459.

Client, Server, and Transport may all have timeout fields in which zero = infinity. Instead it should be a reasonable default.

[FiloSottile]

This issue is close to my heart (1, 2, #16100) but while I agree there should be reasonable defaults, I think changing them now would be a full violation of Go 1 compatibility.

A default Server or Client can serve streaming requests today, with any timeout they couldn't.

[mvdan]

Perhaps 1.11 should have high, non-infinity default timeouts, letting people adapt with less of a shock before setting lower, more sensible defaults in 1.12.

[FiloSottile]

I don't think the way we transition matters, IMHO it's a Go 1 compatibility promise violation: there's a specific real documented use case (streaming) that would stop working from one version to the other.

If we want to consider this a security exception, I'm not sure where I stand, but I think that's the frame in which we should evaluate it.

[artyom]

Perhaps the less intrusive change wrt backwards compatibility would be to only set non-zero timeouts on package-level http.ListenAndServe{,TLS} calls which create implicit Server instance, but keep them unchanged on explicitly created Servers?

[andybons]

/cc @bradfitz

[FiloSottile]

At least we should mention the risk in the docs. See #22085

[bradfitz]

In #22982, an instance of this meta bug, I said in https://github.com/golang/go/issues/22982#issuecomment-394828083 :

I sent CL 116356 to add a 5 minute timeout, but right after I mailed it I realized it would break people wanting to do long downloads.

I think the only conservative thing we could do by default is to add some sort of InactivityTimeout, but it's too late for that, so bumping to Go 1.12.

[FiloSottile]

Recording here an idea that someone at GopherCon suggested. (I don't remember who, apologies.)

Even if we can't change the DefaultClient behavior, we could add a DefaultClientWithTimeout, which although ugly and a mouthful, would prominently draw attention to the importance of client timeouts ("officially" endorsing it as a default, and giving us a place in the docs to elaborate), and provide a way to use them that's easy, maintained, and efficient (globally reusing connections).

Not sure how to map this to the server side, though.

[szuecs]

Honestly, I think the DefaultClient is pretty much broken. If you try to traffic switch by changing DNS you can wait forever (or does it recently changed?).
@FiloSottile don’t you think my example is more a bug?

I am also fine with DefaultClientWithTimeout, but something should be changed in go1.

[FiloSottile]

@szuecs If I understand correctly, the issue is that DefaultClient does not respond to changes in the DNS? I can see that being intended behavior due to connection reuse, or maybe due to hostname lookup caching, but in any case that's unrelated to request/response timeouts. Can you open a separate issue and expand on what you expected to happen vs. what actually happened? Thank you!

[szuecs]

@FiloSottile a separate issue is already available https://github.com/golang/go/issues/23427