moby/opts/hosts_windows.go

package opts // import "github.com/docker/docker/opts"

const (
	// TODO Windows. Identify bug in GOLang 1.5.1+ and/or Windows Server 2016 TP5.
	//
	// On Windows, this mitigates a problem with the default options of running
	// a docker client against a local docker daemon on TP5.
	//
	// What was found that if the default host is "localhost", even if the client
	// (and daemon as this is local) is not physically on a network, and the DNS
	// cache is flushed (ipconfig /flushdns), then the client will pause for
	// exactly one second when connecting to the daemon for calls. For example
	// using docker run windowsservercore cmd, the CLI will send a create followed
	// by an attach. You see the delay between the attach finishing and the attach
	// being seen by the daemon.
	//
	// Here's some daemon debug logs with additional debug spew put in. The
	// AfterWriteJSON log is the very last thing the daemon does as part of the
	// create call. The POST /attach is the second CLI call. Notice the second
	// time gap.
	//
	// time="2015-11-06T13:38:37.259627400-08:00" level=debug msg="After createRootfs"
	// time="2015-11-06T13:38:37.263626300-08:00" level=debug msg="After setHostConfig"
	// time="2015-11-06T13:38:37.267631200-08:00" level=debug msg="before createContainerPl...."
	// time="2015-11-06T13:38:37.271629500-08:00" level=debug msg=ToDiskLocking....
	// time="2015-11-06T13:38:37.275643200-08:00" level=debug msg="loggin event...."
	// time="2015-11-06T13:38:37.277627600-08:00" level=debug msg="logged event...."
	// time="2015-11-06T13:38:37.279631800-08:00" level=debug msg="In defer func"
	// time="2015-11-06T13:38:37.282628100-08:00" level=debug msg="After daemon.create"
	// time="2015-11-06T13:38:37.286651700-08:00" level=debug msg="return 2"
	// time="2015-11-06T13:38:37.289629500-08:00" level=debug msg="Returned from daemon.ContainerCreate"
	// time="2015-11-06T13:38:37.311629100-08:00" level=debug msg="After WriteJSON"
	// ... 1 second gap here....
	// time="2015-11-06T13:38:38.317866200-08:00" level=debug msg="Calling POST /v1.22/containers/984758282b842f779e805664b2c95d563adc9a979c8a3973e68c807843ee4757/attach"
	// time="2015-11-06T13:38:38.326882500-08:00" level=info msg="POST /v1.22/containers/984758282b842f779e805664b2c95d563adc9a979c8a3973e68c807843ee4757/attach?stderr=1&stdin=1&stdout=1&stream=1"
	//
	// We suspect this is either a bug introduced in GOLang 1.5.1, or that a change
	// in GOLang 1.5.1 (from 1.4.3) is exposing a bug in Windows. In theory,
	// the Windows networking stack is supposed to resolve "localhost" internally,
	// without hitting DNS, or even reading the hosts file (which is why localhost
	// is commented out in the hosts file on Windows).
	//
	// We have validated that working around this using the actual IPv4 localhost
	// address does not cause the delay.
	//
	// This does not occur with the docker client built with 1.4.3 on the same
	// Windows build, regardless of whether the daemon is built using 1.5.1
	// or 1.4.3. It does not occur on Linux. We also verified we see the same thing
	// on a cross-compiled Windows binary (from Linux).
	//
	// Final note: This is a mitigation, not a 'real' fix. It is still susceptible
	// to the delay if a user were to do 'docker run -H=tcp://localhost:2375...'
	// explicitly.

	// DefaultHTTPHost Default HTTP Host used if only port is provided to -H flag e.g. dockerd -H tcp://:8080
	DefaultHTTPHost = "127.0.0.1"

	// DefaultHost constant defines the default host string used by docker on Windows
	DefaultHost = "npipe://" + DefaultNamedPipe
)