docker: the container runtime as a module, with its tools in Go

Claims node-container-runtime (ADR 0207). Owns the packages, the socket and a weekly prune of dangling images and unused build cache. Serves 18 tools over every container, marking the mesh's. daemon.json, docker.service and the docker group are left to a proposed change: dnsmasq and zsh declare them today, and the controller refuses a second declaration (README).
2026-10-04 12:37:44 +02:00
parent 83a51832d7
commit d4a6008bd6
9 changed files with 2089 additions and 0 deletions
@@ -0,0 +1,59 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// Ran is what a command did: its output, its exit status, and why it never ran to an answer.
+type Ran struct {
+	Stdout string
+	Stderr string
+	Status int
+	// Err is "ENOENT" when the program is not installed, or says it was ended for taking too long.
+	Err string
+}
+
+// Runner runs one command, so every tool can be tested without a daemon.
+type Runner func(ctx context.Context, name string, args ...string) Ran
+
+// CallTimeout is how long one docker command may take: below the runtime's thirty-second call
+// limit, so a daemon that hangs is answered as such rather than as a call the runtime gave up on.
+const CallTimeout = 20 * time.Second
+
+// ExecRunner runs a command on this machine, bounded by CallTimeout.
+func ExecRunner(ctx context.Context, name string, args ...string) Ran {
+	ctx, cancel := context.WithTimeout(ctx, CallTimeout)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, name, args...)
+	var out, errb bytes.Buffer
+	cmd.Stdout, cmd.Stderr = &out, &errb
+	err := cmd.Run()
+	r := Ran{Stdout: out.String(), Stderr: errb.String()}
+	var exitErr *exec.ExitError
+	switch {
+	case errors.Is(ctx.Err(), context.DeadlineExceeded):
+		r.Status, r.Err = 124, fmt.Sprintf("no answer within %d s", int(CallTimeout/time.Second))
+	case errors.Is(err, exec.ErrNotFound):
+		r.Status, r.Err = 127, "ENOENT"
+	case errors.As(err, &exitErr):
+		r.Status = exitErr.ExitCode()
+	case err != nil:
+		r.Status, r.Err = 1, err.Error()
+	}
+	return r
+}
+
+func firstLine(s string) string {
+	for _, l := range strings.Split(s, "\n") {
+		if l = strings.TrimSpace(l); l != "" {
+			return l
+		}
+	}
+	return ""
+}