atelet: poll ateom workload stats into template-level metrics

cmd/atelet/main.go

@@ -101,6 +101,8 @@ var (
 
 	otlpRelaySocket = pflag.String("otlp-relay-socket", ateompath.AteletOTLPSocketPath(), "Unix socket to serve the OTLP relay on, which forwards the node's ateom telemetry to OTEL_EXPORTER_OTLP_ENDPOINT so worker pods need no network path to the collector. Empty disables the relay.")
 
+	actorStatsPollInterval = pflag.Duration("actor-stats-poll-interval", time.Minute, fmt.Sprintf("Actor resource utilization sampling frequency. 0 disables the sampling entirely; minimum accepted value is %v.", minActorStatsPollInterval))
+
 	drainDelay   = pflag.Duration("drain-delay", 0, "How long to keep accepting new RPCs after SIGTERM before starting the gRPC drain.")
 	drainTimeout = pflag.Duration("drain-timeout", 5*time.Minute, "Deadline for the graceful gRPC drain on shutdown. In-flight RPCs still running past it are forcefully cancelled.")
 )
@@ -254,6 +256,20 @@ func main() {
 		serverboot.Fatal(ctx, "Failed to create Kubernetes clients", err)
 	}
 
+	if interval := clampActorStatsPollInterval(ctx, *actorStatsPollInterval); interval > 0 {
+		if statsInst, err := newStatsInstruments(otel.Meter("atelet")); err != nil {
+			// Telemetry must not take the node's lifecycle daemon down with
+			// it. Instrument creation only fails on programmer error
+			// (conflicting registration), which the poller's own tests catch
+			// in CI -- and the poller has an official disabled state, so a
+			// broken one degrades to that state, loudly, instead of
+			// crash-looping every actor operation on the node.
+			slog.ErrorContext(ctx, "Actor stats sampling disabled: failed to create instruments", slog.Any("err", err))
+		} else {
+			startStatsPoller(ctx, interval, statsInst, ateomDialer, k8sClient)
+		}
+	}
+
 	// TODO: Revisit scalability implications of using a shared informer. This lister
 	// is unlikely to be used with frequency.
 	ateFactory := externalversions.NewSharedInformerFactory(ateClient, 0)