feat: agent enumerates docker containers

agent/internal/workloads/docker.go

@@ -0,0 +1,141 @@
+package workloads
+
+import (
+	"context"
+	"encoding/json"
+	"os/exec"
+	"sort"
+	"strings"
+	"time"
+)
+
+// Workload is one container or one systemd unit, agent-side. It mirrors
+// models.Workload on the server.
+type Workload struct {
+	Kind      string
+	ID        string
+	Name      string
+	State     string
+	Health    string
+	Image     string
+	Stack     string
+	Ports     []string
+	Restarts  int
+	StartedAt time.Time
+	Protected bool
+}
+
+const dockerTimeout = 30 * time.Second
+
+// dockerInspect is the subset of `docker inspect` output we read.
+//
+// We use inspect rather than `docker ps --format '{{json .}}'` because ps
+// reports health and uptime inside a human Status string — "Up 2 hours
+// (healthy)" — and anything built on that is parsing English that is
+// localised, reworded between releases, and silently different for a paused or
+// restarting container. inspect gives typed fields instead.
+type dockerInspect struct {
+	ID    string `json:"Id"`
+	Name  string `json:"Name"`
+	State struct {
+		Status     string `json:"Status"`
+		StartedAt  string `json:"StartedAt"`
+		Restarting bool   `json:"Restarting"`
+		Health     *struct {
+			Status string `json:"Status"`
+		} `json:"Health"`
+	} `json:"State"`
+	Config struct {
+		Image  string            `json:"Image"`
+		Labels map[string]string `json:"Labels"`
+	} `json:"Config"`
+	RestartCount    int `json:"RestartCount"`
+	NetworkSettings struct {
+		Ports map[string][]struct {
+			HostIP   string `json:"HostIp"`
+			HostPort string `json:"HostPort"`
+		} `json:"Ports"`
+	} `json:"NetworkSettings"`
+}
+
+// collectDocker enumerates containers. It returns ok=false with an empty error
+// string when Docker is simply not installed — the common case on this fleet,
+// and not a fault.
+func collectDocker(ctx context.Context) ([]Workload, bool, string) {
+	if _, err := exec.LookPath("docker"); err != nil {
+		return nil, false, "" // not installed; not an error
+	}
+
+	ctx, cancel := context.WithTimeout(ctx, dockerTimeout)
+	defer cancel()
+
+	idsOut, err := exec.CommandContext(ctx, "docker", "ps", "-aq").Output()
+	if err != nil {
+		// Installed but not answering: a different problem with a different
+		// fix, so it carries a message where "not installed" does not.
+		return nil, false, "docker ps failed: " + errText(err)
+	}
+
+	ids := strings.Fields(string(idsOut))
+	if len(ids) == 0 {
+		return []Workload{}, true, "" // Docker present, nothing running
+	}
+
+	args := append([]string{"inspect", "--format", "{{json .}}"}, ids...)
+	out, err := exec.CommandContext(ctx, "docker", args...).Output()
+	if err != nil {
+		return nil, false, "docker inspect failed: " + errText(err)
+	}
+
+	var wls []Workload
+	for _, line := range strings.Split(string(out), "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		var di dockerInspect
+		if err := json.Unmarshal([]byte(line), &di); err != nil {
+			continue
+		}
+		wls = append(wls, dockerToWorkload(di))
+	}
+	return wls, true, ""
+}
+
+func dockerToWorkload(di dockerInspect) Workload {
+	w := Workload{
+		Kind:     "container",
+		ID:       di.ID,
+		Name:     strings.TrimPrefix(di.Name, "/"),
+		State:    di.State.Status,
+		Image:    di.Config.Image,
+		Restarts: di.RestartCount,
+	}
+	if di.State.Health != nil {
+		w.Health = strings.ToLower(di.State.Health.Status)
+	}
+	// The compose project label is what Docker itself treats as authoritative.
+	// No YAML is read from disk: a compose file there may not be what is running.
+	if v := di.Config.Labels["com.docker.compose.project"]; v != "" {
+		w.Stack = v
+	}
+	if t, err := time.Parse(time.RFC3339Nano, di.State.StartedAt); err == nil {
+		w.StartedAt = t
+	}
+	for container, bindings := range di.NetworkSettings.Ports {
+		for _, b := range bindings {
+			w.Ports = append(w.Ports, b.HostIP+":"+b.HostPort+"->"+container)
+		}
+	}
+	// Map iteration order is random; sort so a stored snapshot does not reorder
+	// its own ports between two otherwise identical reports.
+	sort.Strings(w.Ports)
+	return w
+}
+
+func errText(err error) string {
+	if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
+		return strings.TrimSpace(string(ee.Stderr))
+	}
+	return err.Error()
+}