Use Config.VMID as Firecracker's instance ID

Firecracker is internally has an instance ID, but the SDK didn't have
the way to configure the ID. This change connects Config.VMID to the
instance ID.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

Author: kzys

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) {