Use Config.VMID as Firecracker's instance ID

jailer_test.go

@@ -320,6 +320,7 @@ func TestJail(t *testing.T) {
 				},
 			}
 			cfg := &Config{
+				VMID:       "vmid",
 				JailerCfg:  &c.jailerCfg,
 				NetNS:      c.netns,
 				SocketPath: c.socketPath,

machine.go

@@ -137,9 +137,9 @@ type Config struct {
 	JailerCfg *JailerConfig
 
 	// (Optional) VMID is a unique identifier for this VM. It's set to a
-	// random uuid if not provided by the user. It's currently used to
-	// set the CNI ContainerID and create a network namespace path if
-	// CNI configuration is provided as part of NetworkInterfaces
+	// random uuid if not provided by the user. It's used to set Firecracker's instance ID.
+	// If CNI configuration is provided as part of NetworkInterfaces,
+	// the VMID is used to set CNI ContainerID and create a network namespace path.
 	VMID string
 
 	// NetNS represents the path to a network namespace handle. If present, the
@@ -303,13 +303,27 @@ func (m *Machine) LogLevel() string {
 	return m.Cfg.LogLevel
 }
 
+func configureBuilder(builder VMCommandBuilder, cfg Config) VMCommandBuilder {
+	return builder.
+		WithSocketPath(cfg.SocketPath).
+		AddArgs("--seccomp-level", cfg.SeccompLevel.String(), "--id", cfg.VMID)
+}
+
 // NewMachine initializes a new Machine instance and performs validation of the
 // provided Config.
 func NewMachine(ctx context.Context, cfg Config, opts ...Opt) (*Machine, error) {
 	m := &Machine{
 		exitCh: make(chan struct{}),
 	}
 
+	if cfg.VMID == "" {
+		randomID, err := uuid.NewV4()
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to create random ID for VMID")
+		}
+		cfg.VMID = randomID.String()
+	}
+
 	m.Handlers = defaultHandlers
 
 	if cfg.JailerCfg != nil {
@@ -319,10 +333,7 @@ func NewMachine(ctx context.Context, cfg Config, opts ...Opt) (*Machine, error)
 		}
 	} else {
 		m.Handlers.Validation = m.Handlers.Validation.Append(ConfigValidationHandler)
-		m.cmd = defaultFirecrackerVMMCommandBuilder.
-			WithSocketPath(cfg.SocketPath).
-			AddArgs("--seccomp-level", cfg.SeccompLevel.String()).
-			Build(ctx)
+		m.cmd = configureBuilder(defaultFirecrackerVMMCommandBuilder, cfg).Build(ctx)
 	}
 
 	for _, opt := range opts {
@@ -339,14 +350,6 @@ func NewMachine(ctx context.Context, cfg Config, opts ...Opt) (*Machine, error)
 		m.client = NewClient(cfg.SocketPath, m.logger, false)
 	}
 
-	if cfg.VMID == "" {
-		randomID, err := uuid.NewV4()
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to create random ID for VMID")
-		}
-		cfg.VMID = randomID.String()
-	}
-
 	if cfg.ForwardSignals == nil {
 		cfg.ForwardSignals = []os.Signal{
 			os.Interrupt,

machine_test.go

@@ -420,13 +420,17 @@ func TestStartVMM(t *testing.T) {
 }
 
 func TestLogAndMetrics(t *testing.T) {
+	const logLevel = "DEBUG"
+	const vmID = "UserSuppliedVMID"
+
 	dir, err := ioutil.TempDir("", t.Name())
 	require.NoError(t, err)
 	defer os.RemoveAll(dir)
 
 	socketPath := filepath.Join(dir, "fc.sock")
 
 	cfg := Config{
+		VMID:              vmID,
 		SocketPath:        socketPath,
 		DisableValidation: true,
 		KernelImagePath:   getVmlinuxPath(t),
@@ -438,13 +442,10 @@ func TestLogAndMetrics(t *testing.T) {
 		},
 		MetricsPath: filepath.Join(dir, "fc-metrics.out"),
 		LogPath:     filepath.Join(dir, "fc.log"),
-		LogLevel:    "Debug",
+		LogLevel:    logLevel,
 	}
 	ctx := context.Background()
-	cmd := VMCommandBuilder{}.
-		WithSocketPath(cfg.SocketPath).
-		WithBin(getFirecrackerBinaryPath()).
-		Build(ctx)
+	cmd := configureBuilder(VMCommandBuilder{}.WithBin(getFirecrackerBinaryPath()), cfg).Build(ctx)
 	m, err := NewMachine(ctx, cfg, WithProcessRunner(cmd), WithLogger(fctesting.NewLogEntry(t)))
 	require.NoError(t, err)
 
@@ -472,6 +473,10 @@ func TestLogAndMetrics(t *testing.T) {
 	log, err := os.Stat(cfg.LogPath)
 	require.NoError(t, err)
 	assert.NotEqual(t, 0, log.Size())
+
+	content, err := ioutil.ReadFile(cfg.LogPath)
+	require.NoError(t, err)
+	assert.Contains(t, string(content), "["+vmID+":"+logLevel+"]")
 }
 
 func TestStartVMMOnce(t *testing.T) {