service: decouple state polling from media scans

pkg/service/app.go

@@ -107,6 +107,12 @@ type ArtifactSummary struct {
 	SizeBytes   int64     `json:"size_bytes"`
 }
 
+type deviceSnapshot struct {
+	Devices   []Device
+	Err       string
+	CheckedAt time.Time
+}
+
 // App coordinates builds, flashes, sentinel snapshots, and the web UI state.
 type App struct {
 	settings  Settings
@@ -118,6 +124,7 @@ type App struct {
 	snapshots     map[string]SnapshotRecord
 	targets       map[string]facts.Targets
 	artifactStore map[string]ArtifactSummary
+	deviceStore   map[string]deviceSnapshot
 }
 
 // NewApp creates a Metis service app instance.
@@ -143,6 +150,7 @@ func NewApp(settings Settings) (*App, error) {
 		snapshots:     map[string]SnapshotRecord{},
 		targets:       map[string]facts.Targets{},
 		artifactStore: map[string]ArtifactSummary{},
+		deviceStore:   map[string]deviceSnapshot{},
 	}
 	_ = app.loadSnapshots()
 	_ = app.loadTargets()
@@ -180,7 +188,7 @@ func (a *App) State(deviceHost string) PageState {
 	})
 
 	flashHosts := a.flashHosts()
-	devices, deviceErr := a.ListDevices(deviceHost)
+	devices, deviceErr := a.cachedDevices(deviceHost)
 	preferredDevice := preferredDevice(devices)
 	return PageState{
 		LocalHost:        a.settings.LocalHost,
@@ -614,6 +622,52 @@ func errorString(err error) string {
 	return err.Error()
 }
 
+func cloneDevices(devices []Device) []Device {
+	if len(devices) == 0 {
+		return nil
+	}
+	out := make([]Device, len(devices))
+	copy(out, devices)
+	return out
+}
+
+func (a *App) cachedDevices(host string) ([]Device, error) {
+	host = strings.TrimSpace(host)
+	if host == "" {
+		host = a.settings.DefaultFlashHost
+	}
+	a.mu.RLock()
+	snapshot, ok := a.deviceStore[host]
+	a.mu.RUnlock()
+	if !ok {
+		return nil, nil
+	}
+	if strings.TrimSpace(snapshot.Err) != "" {
+		return cloneDevices(snapshot.Devices), errors.New(snapshot.Err)
+	}
+	return cloneDevices(snapshot.Devices), nil
+}
+
+func (a *App) recordDevices(host string, devices []Device, err error) {
+	host = strings.TrimSpace(host)
+	if host == "" {
+		host = a.settings.DefaultFlashHost
+	}
+	snapshot := deviceSnapshot{
+		Devices:   cloneDevices(devices),
+		CheckedAt: time.Now().UTC(),
+	}
+	if err != nil {
+		snapshot.Err = err.Error()
+	}
+	a.mu.Lock()
+	if existing, ok := a.deviceStore[host]; ok && len(snapshot.Devices) == 0 {
+		snapshot.Devices = cloneDevices(existing.Devices)
+	}
+	a.deviceStore[host] = snapshot
+	a.mu.Unlock()
+}
+
 func deviceScore(device Device) int {
 	score := 0
 	model := strings.ToLower(strings.TrimSpace(device.Model))

pkg/service/cluster.go

@@ -270,9 +270,9 @@ func (a *App) remotePodState(kube *kubeClient, podName string) (podState, error)
 		}
 		if strings.TrimSpace(terminated.Reason) != "" {
 			out.Reason = terminated.Reason
-			if strings.TrimSpace(terminated.Message) != "" {
-				out.Message = terminated.Message
-			}
+		}
+		if strings.TrimSpace(terminated.Message) != "" {
+			out.Message = terminated.Message
 		}
 	}
 	return out, nil

pkg/service/remote.go

@@ -15,6 +15,10 @@ import (
 const hostTmpDevicePath = "hosttmp:///tmp"
 
 func (a *App) ListDevices(host string) ([]Device, error) {
+	return a.cachedDevices(host)
+}
+
+func (a *App) RefreshDevices(host string) ([]Device, error) {
 	if host == "" {
 		host = a.settings.DefaultFlashHost
 	}
@@ -24,22 +28,29 @@ func (a *App) ListDevices(host string) ([]Device, error) {
 	}
 	target, ok := nodeMap[host]
 	if !ok {
-		return nil, fmt.Errorf("flash host %s is not a current cluster node", host)
+		err := fmt.Errorf("flash host %s is not a current cluster node", host)
+		a.recordDevices(host, nil, err)
+		return nil, err
 	}
 	image := a.podImageForArch(target.Arch)
 	if image == "" {
-		return nil, fmt.Errorf("no runner image configured for arch %s", target.Arch)
+		err := fmt.Errorf("no runner image configured for arch %s", target.Arch)
+		a.recordDevices(host, nil, err)
+		return nil, err
 	}
 	podName := fmt.Sprintf("metis-devices-%d", time.Now().UTC().UnixNano())
 	logs, err := a.runRemotePod("", podName, a.remoteDevicePodSpec(podName, host, image))
 	if err != nil {
+		a.recordDevices(host, nil, err)
 		return nil, err
 	}
 	var payload struct {
 		Devices []Device `json:"devices"`
 	}
 	if err := json.Unmarshal([]byte(strings.TrimSpace(logs)), &payload); err != nil {
-		return nil, fmt.Errorf("decode remote devices: %w: %s", err, strings.TrimSpace(logs))
+		decodeErr := fmt.Errorf("decode remote devices: %w: %s", err, strings.TrimSpace(logs))
+		a.recordDevices(host, nil, decodeErr)
+		return nil, decodeErr
 	}
 	sort.Slice(payload.Devices, func(i, j int) bool {
 		left := deviceScore(payload.Devices[i])
@@ -52,6 +63,7 @@ func (a *App) ListDevices(host string) ([]Device, error) {
 		}
 		return payload.Devices[i].Path < payload.Devices[j].Path
 	})
+	a.recordDevices(host, payload.Devices, nil)
 	return payload.Devices, nil
 }
 
@@ -319,7 +331,7 @@ func (a *App) ensureDevice(host, path string) (*Device, error) {
 	if strings.TrimSpace(path) == "" {
 		return nil, fmt.Errorf("select removable media before starting a flash run")
 	}
-	devices, err := a.ListDevices(host)
+	devices, err := a.RefreshDevices(host)
 	if err != nil {
 		return nil, err
 	}

pkg/service/server.go

@@ -82,7 +82,7 @@ func (a *App) handleState(w http.ResponseWriter, r *http.Request) {
 
 func (a *App) handleDevices(w http.ResponseWriter, r *http.Request) {
 	host := r.URL.Query().Get("host")
-	devices, err := a.ListDevices(host)
+	devices, err := a.RefreshDevices(host)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
@@ -815,6 +815,20 @@ var metisPage = template.Must(template.New("metis").Parse(`<!doctype html>
       }
     }
 
+    async function refreshDevices(){
+      const host = hostSelect.value || state.default_flash_host;
+      const resp = await fetch('/api/devices?host=' + encodeURIComponent(host));
+      if(!resp.ok){
+        const text = await resp.text();
+        throw new Error(text || 'Could not refresh removable media');
+      }
+      const payload = await resp.json();
+      state.devices = payload.devices || [];
+      state.selected_host = host;
+      state.device_error = '';
+      render();
+    }
+
     async function post(path, body){
       const resp = await fetch(path, {
         method:'POST',
@@ -856,7 +870,8 @@ var metisPage = template.Must(template.New("metis").Parse(`<!doctype html>
 
     document.getElementById('refresh-devices').addEventListener('click', async ()=>{
       await runAction('Refreshing media', 'Checking removable devices on the selected flash host.', async ()=>{
-        await refreshState();
+        await refreshDevices();
+        await refreshState({silent:true});
         if(state.device_error){
           banner('warn', 'Flash host needs attention', state.device_error);
           return;
@@ -904,7 +919,9 @@ var metisPage = template.Must(template.New("metis").Parse(`<!doctype html>
 
     hostSelect.addEventListener('change', async ()=>{
       await runAction('Changing flash host', 'Loading removable media candidates for the selected flash host.', async ()=>{
-        await refreshState();
+        await refreshState({silent:true});
+        await refreshDevices();
+        await refreshState({silent:true});
         if(!state.device_error){
           banner('success', 'Flash host ready', 'Loaded removable media candidates for ' + (hostSelect.value || state.default_flash_host) + '.');
         }
@@ -914,13 +931,24 @@ var metisPage = template.Must(template.New("metis").Parse(`<!doctype html>
 
     render();
     clearBanner();
-    setInterval(async ()=>{
+    (async ()=>{
+      try {
+        await refreshDevices();
+      } catch (_error) {
+        // Initial media scan can fail if the selected host is unavailable.
+      }
+    })();
+
+    async function pollLoop(){
       try {
         await refreshState({silent:true});
       } catch (_error) {
         // Keep the live dashboard calm during background polling.
       }
-    }, 5000);
+      const running = (state.jobs || []).some((job)=>job.status === 'running');
+      setTimeout(pollLoop, running ? 2000 : 5000);
+    }
+    pollLoop();
   </script>
 </body>
 </html>`))