feat: add optional InstanceID field to log output

.devcontainer/host-metering.conf

@@ -18,3 +18,4 @@ write_retry_max_int_sec=2
 metrics_wal_path=./mocks/cpumetrics
 metrics_max_age_sec=30
 log_level=DEBUG
+instance_id=

config/config.go

@@ -31,6 +31,7 @@ const (
 	DefaultMetricsWALPath       = "/var/run/host-metering/metrics"
 	DefaultLogLevel             = "INFO"
 	DefaultLogPath              = "" //Default to stderr, will be logged in journal.
+	DefaultInstanceID           = ""
 )
 
 type Config struct {
@@ -49,6 +50,7 @@ type Config struct {
 	MetricsWALPath       string
 	LogLevel             string // one of "ERROR", "WARN", "INFO", "DEBUG", "TRACE"
 	LogPath              string
+	InstanceID           string
 }
 
 func NewConfig() *Config {
@@ -68,6 +70,7 @@ func NewConfig() *Config {
 		MetricsWALPath:       DefaultMetricsWALPath,
 		LogLevel:             DefaultLogLevel,
 		LogPath:              DefaultLogPath,
+		InstanceID:           DefaultInstanceID,
 	}
 }
 
@@ -90,6 +93,7 @@ func (c *Config) String() string {
 			fmt.Sprintf("|  MetricsWALPath: %s", c.MetricsWALPath),
 			fmt.Sprintf("|  LogLevel: %s", c.LogLevel),
 			fmt.Sprintf("|  LogPath: %s", c.LogPath),
+			fmt.Sprintf("|  InstanceID: %s", c.InstanceID),
 		}, "\n")
 }
 
@@ -150,6 +154,9 @@ func (c *Config) UpdateFromEnvVars() error {
 	if v := os.Getenv("HOST_METERING_LOG_PATH"); v != "" {
 		c.LogPath = v
 	}
+	if v := os.Getenv("HOST_METERING_INSTANCE_ID"); v != "" {
+		c.InstanceID = v
+	}
 	return multiError.ErrorOrNil()
 }
 
@@ -267,6 +274,9 @@ func (c *Config) UpdateFromConfigFile(path string) error {
 	if v, ok := config[section]["log_path"]; ok {
 		c.LogPath = v
 	}
+	if v, ok := config[section]["instance_id"]; ok {
+		c.InstanceID = v
+	}
 
 	return multiError.ErrorOrNil()
 }

config/config_test.go

@@ -26,7 +26,8 @@ func TestDefaultConfig(t *testing.T) {
 		"|  MetricsMaxAgeSec: 5400\n" +
 		"|  MetricsWALPath: /var/run/host-metering/metrics\n" +
 		"|  LogLevel: INFO\n" +
-		"|  LogPath: \n"
+		"|  LogPath: \n" +
+		"|  InstanceID: \n"
 
 	// Create the default configuration.
 	c := NewConfig()
@@ -73,7 +74,8 @@ func TestConfigFile(t *testing.T) {
 		"|  MetricsMaxAgeSec: 700\n" +
 		"|  MetricsWALPath: /tmp/metrics\n" +
 		"|  LogLevel: ERROR\n" +
-		"|  LogPath: /tmp/log\n"
+		"|  LogPath: /tmp/log\n" +
+		"|  InstanceID: test-instance\n"
 
 	// Update the configuration from a valid config file.
 	fileContent := "[host-metering]\n" +
@@ -93,7 +95,9 @@ func TestConfigFile(t *testing.T) {
 		"metrics_max_age_sec = 700\n" +
 		"metrics_wal_path = /tmp/metrics\n" +
 		"log_level = ERROR\n" +
-		"log_path = /tmp/log\n"
+		"log_path = /tmp/log\n" +
+		"instance_id = test-instance\n"
+
 	c := NewConfig()
 
 	createConfigFile(t, path, fileContent)
@@ -151,7 +155,8 @@ func TestEnvVariables(t *testing.T) {
 		"|  MetricsMaxAgeSec: 700\n" +
 		"|  MetricsWALPath: /tmp/metrics\n" +
 		"|  LogLevel: ERROR\n" +
-		"|  LogPath: /tmp/log\n"
+		"|  LogPath: /tmp/log\n" +
+		"|  InstanceID: test-instance\n"
 
 	// Set valid environment variables.
 	t.Setenv("HOST_METERING_WRITE_URL", "http://test/url")
@@ -169,6 +174,7 @@ func TestEnvVariables(t *testing.T) {
 	t.Setenv("HOST_METERING_METRICS_WAL_PATH", "/tmp/metrics")
 	t.Setenv("HOST_METERING_LOG_LEVEL", "ERROR")
 	t.Setenv("HOST_METERING_LOG_PATH", "/tmp/log")
+	t.Setenv("HOST_METERING_INSTANCE_ID", "test-instance")
 
 	// Environment variables are set. Change the defaults.
 	c := NewConfig()
@@ -223,6 +229,7 @@ func clearEnvironment() {
 	_ = os.Unsetenv("HOST_METERING_METRICS_WAL_PATH")
 	_ = os.Unsetenv("HOST_METERING_LOG_LEVEL")
 	_ = os.Unsetenv("HOST_METERING_LOG_PATH")
+	_ = os.Unsetenv("HOST_METERING_INSTANCE_ID")
 }
 
 func checkError(t *testing.T, err error, message string) {

contrib/man/host-metering.1

@@ -89,6 +89,9 @@ Log level. Possible values are: DEBUG, INFO, WARN, ERROR, TRACE.
 \fBHOST_METERING_LOG_PATH\fR
 Path to log file. Default is empty - stderr.
 
+\fBHOST_METERING_INSTANCE_ID\fR
+Instance id. Default is empty.
+
 .SH "FILES"
 .PP
 \fI/etc/host-metering.conf\fR

contrib/man/host-metering.conf.5

@@ -104,6 +104,11 @@ log_path (string)
 Path to log file. Default is empty - stderr.
 .RE
 
+.PP
+instance_id (string)
+.RS 4
+Instance id. Default is empty.
+
 .SH "EXAMPLES"
 .PP
 1\&. The following example shows how to switch the logging to DEBUG level\&.

logger/logger.go

@@ -21,11 +21,20 @@ type Logger logrus.FieldLogger
 type CustomFormatter struct{}
 
 func (f *CustomFormatter) Format(entry *logrus.Entry) ([]byte, error) {
+	var msg string
+
+	instanceID, ok := entry.Data["instance_id"].(string)
+	if ok {
+		msg = fmt.Sprintf("[%s] ", instanceID)
+	}
+
 	message := entry.Message
 	if !strings.HasSuffix(message, "\n") {
 		message += "\n"
 	}
-	msg := fmt.Sprintf("%s %s", entry.Time.Format("2006/01/02 15:04:05"), message)
+
+	msg += fmt.Sprintf("%s %s", entry.Time.Format("2006/01/02 15:04:05"), message)
+
 	return []byte(msg), nil
 }
 
@@ -35,7 +44,7 @@ func InitDefaultLogger() Logger {
 	return logger
 }
 
-func InitLogger(file string, level string) error {
+func InitLogger(file string, level string, instanceID string) error {
 	logLevel, err := logrus.ParseLevel(level)
 
 	if err != nil {
@@ -56,6 +65,10 @@ func InitLogger(file string, level string) error {
 		Level:     logLevel,
 	}
 
+	if instanceID != "" {
+		log = log.WithField("instance_id", instanceID)
+	}
+
 	return nil
 }
 

logger/logger_test.go

@@ -39,7 +39,7 @@ func TestLoggerGlobalFunctions(t *testing.T) {
 
 // Test initialization of logger with only log level
 func TestInitLogger(t *testing.T) {
-	InitLogger("", DebugLevel.String())
+	InitLogger("", DebugLevel.String(), "")
 	if log == nil {
 		t.Fatalf("logger is not initialized")
 	}
@@ -51,7 +51,7 @@ func TestInitLogger(t *testing.T) {
 func TestInitLoggerFile(t *testing.T) {
 	dir := t.TempDir()
 	path := dir + "/test.log"
-	InitLogger(path, DebugLevel.String())
+	InitLogger(path, DebugLevel.String(), "test_instance")
 	if log == nil {
 		t.Fatalf("logger is not initialized")
 	}
@@ -64,14 +64,17 @@ func TestInitLoggerFile(t *testing.T) {
 		t.Fatalf("log file is not created")
 	}
 
-	// Check that the file contains the logger message
+	// Check that the file contains the instanceID and logger message
 	data, err := os.ReadFile(path)
 	if err != nil {
 		t.Fatalf("cannot read the log file")
 	}
 	if !strings.Contains(string(data), testMsg) {
 		t.Fatalf("log file does not contain the logged message")
 	}
+	if !strings.HasPrefix(string(data), "[test_instance]") {
+		t.Errorf("Expected the output to start with '[test_instance]', but got: %s", string(data))
+	}
 }
 
 // Test that logger can be raplaced by other implementation of Logger interface.

main.go

@@ -47,7 +47,7 @@ func main() {
 		}
 
 		// initialize the logger according to the given configuration
-		err = logger.InitLogger(cfg.LogPath, cfg.LogLevel)
+		err = logger.InitLogger(cfg.LogPath, cfg.LogLevel, cfg.InstanceID)
 
 		if err != nil {
 			logger.Debugf("Error initializing logger: %s\n", err.Error())