kraftkit Examples not working on Arch without proper Docker setup

[cluosh]

Describe the bug

During the Unikraft Workshop we discovered that kraftkit does not give a proper error message on Arch LInux if Docker is not installed/started/we do not have the correct permissions.

Steps to reproduce

Install kraftkit-bin from the AUR and don't start docker beforehand

Expected behavior

An error message that docker needs to be started/installed/user has correct permissions

Which architectures were you using or does this bug affect?

x86_64

Which operating system were you using or does this bug affect?

linux/arch

Relevant log output

i  use --as=kraftfile-runtime to skip this prompt in the future
Caught panic:

checked path: $XDG_RUNTIME_DIR

Restoring terminal...

goroutine 232 [running]:
runtime/debug.Stack()
	/usr/local/go/src/runtime/debug/stack.go:24 +0x5e
runtime/debug.PrintStack()
	/usr/local/go/src/runtime/debug/stack.go:16 +0x13
github.com/charmbracelet/bubbletea.(*Program).recoverFromPanic(0xc000143900)
	/go/pkg/mod/github.com/charmbracelet/[email protected]/tea.go:705 +0x91
panic({0x1e63bc0?, 0xc00048d3f8?})
	/usr/local/go/src/runtime/panic.go:770 +0x132
github.com/testcontainers/testcontainers-go/internal/core.MustExtractDockerHost.func1()
	/go/pkg/mod/github.com/testcontainers/[email protected]/internal/core/docker_host.go:91 +0x66
sync.(*Once).doSlow(0xc000aabc30?, 0xc000aabc80?)
	/usr/local/go/src/sync/once.go:74 +0xc2
sync.(*Once).Do(...)
	/usr/local/go/src/sync/once.go:65
github.com/testcontainers/testcontainers-go/internal/core.MustExtractDockerHost({0x2592198?, 0x37abcc0?})
	/go/pkg/mod/github.com/testcontainers/[email protected]/internal/core/docker_host.go:88 +0x58
github.com/testcontainers/testcontainers-go/internal/core.NewClient({0x2592198, 0x37abcc0}, {0x0, 0x0, 0x0?})
	/go/pkg/mod/github.com/testcontainers/[email protected]/internal/core/client.go:17 +0x88
github.com/testcontainers/testcontainers-go.NewDockerClientWithOpts({0x2592198, 0x37abcc0}, {0x0, 0x0, 0x0})
	/go/pkg/mod/github.com/testcontainers/[email protected]/docker_client.go:117 +0x71
github.com/testcontainers/testcontainers-go.NewDockerProvider({0xc0007ab560, 0x2, 0x21c1d7f?})
	/go/pkg/mod/github.com/testcontainers/[email protected]/provider.go:143 +0x10f
github.com/testcontainers/testcontainers-go.ProviderType.GetProvider(0x0, {0xc000aace28, 0x1, 0x586d1a?})
	/go/pkg/mod/github.com/testcontainers/[email protected]/provider.go:114 +0x3e5
github.com/testcontainers/testcontainers-go.GenericContainer({_, _}, {{{{0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, ...}, ...}, ...})
	/go/pkg/mod/github.com/testcontainers/[email protected]/generic.go:59 +0x139
kraftkit.sh/initrd.(*dockerfile).Build(0xc000181c20, {0x25920b8, 0xc00071d6b0})
	/__w/kraftkit/kraftkit/initrd/dockerfile.go:283 +0xad9
kraftkit.sh/internal/cli/kraft/utils.BuildRootfs.func1({0x25920b8?, 0xc00071d6b0?})
	/__w/kraftkit/kraftkit/internal/cli/kraft/utils/rootfs.go:55 +0x63
kraftkit.sh/tui/processtree.(*ProcessTree).Init.(*ProcessTree).waitForProcessCmd.func2()
	/__w/kraftkit/kraftkit/tui/processtree/processtree.go:334 +0x11a
github.com/charmbracelet/bubbletea.(*Program).handleCommands.func1.1()
	/go/pkg/mod/github.com/charmbracelet/[email protected]/tea.go:324 +0x86
created by github.com/charmbracelet/bubbletea.(*Program).handleCommands.func1 in goroutine 227
	/go/pkg/mod/github.com/charmbracelet/[email protected]/tea.go:318 +0x139
 E  could not prepare deployment: could not package: could not package: could not build rootfs: program was killed: context canceled

[craciunoiuc]

This looks like a panic generated by a library we use, and indeed the line that generates it is a library call.

I think it is easiest if we just wait for a fix in testcontainers to come out, before attempting any workaround.

Glad that you fixed the problem though!

[craciunoiuc]

Update: I tracked down the code in their library and found this function deep down:

// MustExtractDockerHost Extracts the docker host from the different alternatives, caching the result to avoid unnecessary
// calculations. Use this function to get the actual Docker host. This function does not consider Windows containers at the moment.
// The possible alternatives are:
//
//  1. Docker host from the "tc.host" property in the ~/.testcontainers.properties file.
//  2. DOCKER_HOST environment variable.
//  3. Docker host from context.
//  4. Docker host from the default docker socket path, without the unix schema.
//  5. Docker host from the "docker.host" property in the ~/.testcontainers.properties file.
//  6. Rootless docker socket path.
//  7. Else, because the Docker host is not set, it panics.
func MustExtractDockerHost(ctx context.Context) string {
	dockerHostOnce.Do(func() {
		cache, err := extractDockerHost(ctx)
		if err != nil {
			panic(err)
		}

		dockerHostCache = cache
	})

	return dockerHostCache
}

Notice that on step 7 it says that it just panics if it doesn't find anything.

I will try to catch/interpret this to give out a better error, but there's nothing more that can be done.