Set keepalive on TCP socket so idleTimeout works

[ajardan]

What does this PR do?

This makes traefik set KeepAlive on TCP connections it accepts, which fixes #3263 and possibly other issues related to socket leak, or file descriptor exhaustion.

Without this change, the configuration option

--respondingtimeouts.idletimeout

has no effect, since it only works for keep-alive connections according to this document:

https://golang.org/src/net/http/server.go?s=93090:93158#L2443

Motivation

This is a relatively trivial change that improves how traefik performs and increases its performance and stability.

More

• Added/updated tests
• Added/updated documentation

Additional Notes

I am not actually the author of this code, it is taken from the net.http.Server package, original source here:

https://golang.org/src/net/http/server.go?s=93090:93158#L3207

[ajardan]

The build failed, but the reason of failure doesn't seem to be related with the introduced changes. What is the procedure in such cases ?

LogRotationSuite.TestTraefikLogRotation: No Traefik logs.
remove traefik.log: no such file or directory
INFO[0608] LogRotationSuite.TestTraefikLogRotation: No Traefik logs. 

----------------------------------------------------------------------
FAIL: log_rotation_test.go:87: LogRotationSuite.TestTraefikLogRotation

log_rotation_test.go:117:
    c.Assert(err, checker.IsNil)
... value *errors.errorString = &errors.errorString{s:"try operation failed: stat traefik.log: no such file or directory"} ("try operation failed: stat traefik.log: no such file or directory")

[ldez]

The real problem:

NFO[0009] ProxyProtocolSuite.TestProxyProtocolNotTrusted: Traefik logs:  
INFO[0009] time="2018-08-06T18:13:58Z" level=info msg="Using TOML configuration file /home/runner/workspace/src/github.com/containous/traefik/integration/fixtures/proxy-protocol/without.toml828478900"
time="2018-08-06T18:13:58Z" level=info msg="Traefik version 6e47001797f2fe5f7cf5c80d6f55ad3b7c0b348f built on 2018-08-06_06:01:19PM"
time="2018-08-06T18:13:58Z" level=info msg="\nStats collection is disabled.\nHelp us improve Traefik by turning this feature on :)\nMore details on: https://docs.traefik.io/basics/#collected-data\n"
time="2018-08-06T18:13:58Z" level=debug msg="Global configuration loaded "
time="2018-08-06T18:13:58Z" level=info msg="Preparing server traefik &{Address::8080 TLS:<nil> Redirect:<nil> Auth:<nil> WhitelistSourceRange:[] WhiteList:<nil> Compress:false ProxyProtocol:<nil> ForwardedHeaders:0xc4201c7b40} with readTimeout=0s writeTimeout=0s idleTimeout=3m0s"
time="2018-08-06T18:13:58Z" level=info msg="Preparing server http &{Address::8000 TLS:<nil> Redirect:<nil> Auth:<nil> WhitelistSourceRange:[] WhiteList:<nil> Compress:false ProxyProtocol:0xc4201c69c0 ForwardedHeaders:0xc4201c7b20} with readTimeout=0s writeTimeout=0s idleTimeout=3m0s"
time="2018-08-06T18:13:58Z" level=info msg="Enabling ProxyProtocol for trusted IPs [1.2.3.4]"
time="2018-08-06T18:13:58Z" level=info msg="Starting provider configuration.ProviderAggregator {}"
time="2018-08-06T18:13:58Z" level=info msg="Starting server on :8080"
time="2018-08-06T18:13:58Z" level=info msg="Starting server on :8000"
panic: interface conversion: net.Listener is *proxyproto.Listener, not *net.TCPListener

goroutine 51 [running]:
github.com/containous/traefik/h2c.Server.Serve(0xc4209da0d0, 0x26827c0, 0xc4205f5440, 0x1, 0x1)
	/go/src/github.com/containous/traefik/h2c/h2c.go:99 +0x14e
github.com/containous/traefik/server.(*Server).startServer(0xc42096c000, 0xc4201d21c0)
	/go/src/github.com/containous/traefik/server/server.go:503 +0x1c0
created by github.com/containous/traefik/server.(*Server).startHTTPServers
	/go/src/github.com/containous/traefik/server/server.go:325 +0x101
 

----------------------------------------------------------------------
FAIL: proxy_protocol_test.go:41: ProxyProtocolSuite.TestProxyProtocolNotTrusted

proxy_protocol_test.go:58:
    c.Assert(err, checker.IsNil)
... value *errors.errorString = &errors.errorString{s:"try operation failed: Get http://172.17.0.3/whoami: EOF"} ("try operation failed: Get http://172.17.0.3/whoami: EOF")

[juliens]

👏
This is a really good fix! Thank you
But I think it should be better to do it here
https://github.com/containous/traefik/blob/bb331285522b2734fc36b5cde0c9c5170c4ffcfe/server/server.go#L558

[ajardan]

@juliens Moved it to server as you recommended, but not sure in the "best way". It fixed the ProxyProtocol tests though :)

@ldez Thanks a lot for pointing me to the right error, missed that somehow. Will look better next time.

[juliens]

LGTM

[nmengin]

Many thanks for this PR @ajardan

LGTM 👏 👏 👍

[ldez]

LGTM