Allow switching Windows runtimes.

[cpuguy83]

This adds support for 2 runtimes on Windows, one that uses the built-in
HCSv1 integration and another which uses containerd with the runhcs
shim.

---

Related to #41455

[olljanat]

Looks that finding runtime binaries with this logic fails to error:

specified default runtime 'io.containerd.runhcs.v1' does not exist

Way how I set it on #41479 works.

Which is enabling experimental mode + DOCKER_WINDOWS_CONTAINERD_RUNTIME which are called on:

moby/pkg/system/init_windows.go

Lines 15 to 29 in 46cdcd2

	// InitContainerdRuntime sets whether to use ContainerD for runtime
	// on Windows. This is an experimental feature still in development, and
	// also requires an environment variable to be set (so as not to turn the
	// feature on from simply experimental which would also mean LCOW.
	func InitContainerdRuntime(experimental bool, cdPath string) {
	if experimental && len(cdPath) > 0 && len(os.Getenv("DOCKER_WINDOWS_CONTAINERD_RUNTIME")) > 0 {
	logrus.Warnf("Using ContainerD runtime. This feature is experimental")
	containerdRuntimeSupported = true
	}
	}
	// ContainerdRuntimeSupported returns true if the use of ContainerD runtime is supported.
	func ContainerdRuntimeSupported() bool {
	return containerdRuntimeSupported
	}

and setting containerd runtime name on:

moby/daemon/start_windows.go

Line 15 in 46cdcd2

return "", opts, nil

[cpuguy83]

Closing this one as I think the work @olljanat is exactly the right way to handle this.
If you want v1, don't specify a containerd socket.

[cpuguy83]

Actually, I take that back. There's some other work I'd like to do (namely embed containerd instead of relying on an external one when no --containerd= is set) that needs this work.

[cpuguy83]

RS5 failures look unrelated.

[tianon]

No cases where we use a default value for the containerd address or anything like that? ISTR some talk about trying to default to V2 on 2022+? (I guess that ship sailed?)

[cpuguy83]

So my plan is to follow-up with a PR to embed containerd and use that if no address is specified on both linux and windows.

[cpuguy83]

That said, even on Linux we don't default a socket here.
On Windows we just don't start a containerd process like we do on Linux.

[tianon]

Ahhh, got it; thanks for the added detail.

[tianon]

Looks pretty straightforward to me 😇

[thaJeztah]

LGTM

[thaJeztah]

The whole StockRuntimeName vs DefaultRuntimeName is a bit confusing.

Wondering, will setting this to an empty string cause some odd behavior if somehow the option is set to an empty string?

moby/opts/runtime.go

Lines 44 to 46 in 7b9275c

	if parts[0] == o.stockRuntimeName {
	return fmt.Errorf("runtime name '%s' is reserved", o.stockRuntimeName)
	}

[thaJeztah]

Ah, never mind; looks like we first check if it's not empty;

moby/opts/runtime.go

Lines 39 to 41 in 7b9275c

	if parts[0] == "" || parts[1] == "" {
	return fmt.Errorf("invalid runtime argument: %s", val)
	}

[thaJeztah]

oh! looks like CI is failing; looks relevant;

ERRO Running error: buildssa: analysis skipped: errors in package: [/go/src/github.com/docker/docker/daemon/config/config_linux_test.go:153:5: unknown field DefaultRuntime in struct literal] 

[thaJeztah]

Could you also open a PR in the CLI repository to update the daemon.json for Windows? (it shows an example with "all options supported by Windows"); https://github.com/docker/cli/blob/master/docs/reference/commandline/dockerd.md#on-windows

[thaJeztah]

This should fix the failure;

diff --git a/daemon/config/config_linux_test.go b/daemon/config/config_linux_test.go
index 424bfc00e6..cfc635567d 100644
--- a/daemon/config/config_linux_test.go
+++ b/daemon/config/config_linux_test.go
@@ -150,7 +150,9 @@ func TestUnixValidateConfigurationErrors(t *testing.T) {
                                Runtimes: map[string]types.Runtime{
                                        "foo": {},
                                },
-                               DefaultRuntime: "bar",
+                               CommonConfig: CommonConfig{
+                                       DefaultRuntime: "bar",
+                               },
                        },
                },
        }

[thaJeztah]

LGTM (assuming green)