feat(agent): add Metrics+NodeName to FirecrackerDriver, share VMMetricsCollector

Add Metrics *VMMetricsCollector and NodeName string fields to
FirecrackerDriver so the pollMetrics goroutine (Task 3) can set guest
gauges with the correct node label. Also add metricsInterval var
following the same override-friendly pattern as shuttingDownTimeout.

newProductionDriver now accepts mc and nodeName so both the driver and
ImpVMReconciler share the same VMMetricsCollector instance.

Author: syscod3

cmd/agent/driver_linux.go

@@ -12,12 +12,14 @@ import (
 // newProductionDriver creates a FirecrackerDriver wired with a LinuxNetManager.
 // Reads FC_BIN, FC_SOCK_DIR, FC_KERNEL, FC_KERNEL_ARGS, and IMP_IMAGE_CACHE.
 // Returns the driver, the shared NetManager, and any error.
-func newProductionDriver(client ctrlclient.Client) (agent.VMDriver, network.NetManager, error) {
+func newProductionDriver(client ctrlclient.Client, mc *agent.VMMetricsCollector, nodeName string) (agent.VMDriver, network.NetManager, error) {
 	d, err := agent.NewFirecrackerDriver(client)
 	if err != nil {
 		return nil, nil, err
 	}
 	nm := network.NewLinuxNetManager()
 	d.Net = nm
+	d.Metrics = mc
+	d.NodeName = nodeName
 	return d, nm, nil
 }

cmd/agent/main.go

@@ -57,6 +57,8 @@ func main() {
 		os.Exit(1)
 	}
 
+	mc := agent.NewVMMetricsCollector()
+
 	// IMP_STUB_DRIVER=true: StubDriver (CI, test clusters, no KVM needed).
 	// Otherwise: FirecrackerDriver (reads FC_BIN, FC_SOCK_DIR, FC_KERNEL env vars).
 	var driver agent.VMDriver
@@ -66,7 +68,7 @@ func main() {
 		driver = agent.NewStubDriver()
 	} else {
 		var fcErr error
-		driver, prodNet, fcErr = newProductionDriver(mgr.GetClient())
+		driver, prodNet, fcErr = newProductionDriver(mgr.GetClient(), mc, nodeName)
 		if fcErr != nil {
 			log.Error(fcErr, "Unable to create FirecrackerDriver — set FC_KERNEL and ensure FC_BIN is in PATH")
 			os.Exit(1)
@@ -80,7 +82,7 @@ func main() {
 		NodeName: nodeName,
 		NodeIP:   nodeIP,
 		Driver:   driver,
-		Metrics:  agent.NewVMMetricsCollector(),
+		Metrics:  mc,
 		Net:      prodNet,
 	}).SetupWithManager(mgr); err != nil {
 		log.Error(err, "Unable to set up ImpVMReconciler")

internal/agent/firecracker_driver.go

@@ -37,6 +37,10 @@ import (
 // before force-killing the VMM. Declared as var (not const) so tests can override it.
 var shuttingDownTimeout = 5 * time.Second
 
+// metricsInterval controls how often guest metrics are polled via VSOCK.
+// Declared as var (not const) so tests can override it.
+var metricsInterval = 30 * time.Second
+
 // fcProc holds the runtime state of a running Firecracker microVM process.
 type fcProc struct {
 	machine      *firecracker.Machine
@@ -69,6 +73,11 @@ type FirecrackerDriver struct {
 	// GuestAgentPath is the host path to the guest-agent binary for injection.
 	// Defaults to rootfs.GuestAgentContainerPath when empty.
 	GuestAgentPath string
+	// Metrics collects Prometheus gauges for guest CPU/mem/disk.
+	// When nil, guest metrics polling is skipped.
+	Metrics *VMMetricsCollector
+	// NodeName is the Kubernetes node name, used as a Prometheus label in guest metrics.
+	NodeName string
 
 	// mu guards procs. Must be held for any read or write of the procs map.
 	mu    sync.Mutex

internal/agent/firecracker_driver_test.go

@@ -549,6 +549,20 @@ func TestFirecrackerDriver_Snapshot_noVM_returnsError(t *testing.T) {
 	}
 }
 
+func TestFirecrackerDriver_HasMetricsAndNodeNameFields(t *testing.T) {
+	d := &FirecrackerDriver{
+		Metrics:  NewVMMetricsCollector(),
+		NodeName: "node-1",
+		procs:    make(map[string]*fcProc),
+	}
+	if d.Metrics == nil {
+		t.Error("Metrics field must be settable on FirecrackerDriver")
+	}
+	if d.NodeName != "node-1" {
+		t.Errorf("NodeName = %q, want %q", d.NodeName, "node-1")
+	}
+}
+
 func TestFirecrackerDriver_Stop_doesNotCallRemoveNATWhenNotLast(t *testing.T) {
 	stub := &network.StubNetManager{}
 	alloc := network.NewAllocator()