Logrus

[mtchuyen]

See: https://itnext.io/elevate-your-golang-logging-with-the-strength-of-logrus-eb028b117c40

Basic Logging with Logrus

Feature:

1. Formatting Logs with Logrus

logrus.SetFormatter(&logrus.JSONFormatter{})

we’re setting the log format to JSON and logging an informational message.

 logrus.Info("This is an informational message.")

you’ll get a JSON-formatted log entry like this:

{"level":"info","msg":"This is an informational message.","time":"2023-07-23T14:56:00Z"}.

1.2. Log Entry Order

You can maintain a consistent order of log entry fields.

func main() {
 logrus.SetFormatter(&logrus.JSONFormatter{FieldMap: logrus.FieldMap{
  logrus.FieldKeyTime:  "@timestamp",
  logrus.FieldKeyLevel: "@level",
  logrus.FieldKeyMsg:   "@message",
 }})
 logrus.Info("Log with consistent field order.")
}

1.3. Custom Log Formatter

You can create custom formatters to control how log entries are formatted.

type CustomFormatter struct{}

func (f *CustomFormatter) Format(entry *logrus.Entry) ([]byte, error) {
  return []byte(fmt.Sprintf("%s: %s\n", entry.Level.String(), entry.Message)), nil
}

func main() {
  logrus.SetFormatter(new(CustomFormatter))
  logrus.Info("Log with a custom formatter.")
}

2. Setting the Log Level

Logrus provides several log levels.

2.3. Logging a Fatal Error:

If you have a severe error that needs to terminate the program, you can use Fatal which logs the error and calls os.Exit(1).

2.4. Logging With a Panic

In case you need to log an error message and panic, use Panic.

logrus.Panic("This is a panic log!")

2.5. Trace level:

If you want even more detail than Debug, Logrus provides a Trace level.

 logrus.SetLevel(logrus.TraceLevel)
 logrus.Trace("This is a trace log.")

2.5. Logging to an io.Writer

 logrus.SetOutput(os.Stdout)
 logrus.Info("This log is written to stdout.")

2.6. Logging in Different Timezones

You can set your preferred timezone for the log timestamps.

// Use UTC time
logrus.SetFormatter(&logrus.JSONFormatter{TimestampFormat: time.RFC3339})
logrus.Info("Log with RFC3339 timestamp format.")

3. Implementing Hooks with Logrus

Logrus hooks can be extremely useful for sending log entries to external services that Logrus don’t already support.

Ref

• Series: Start with Logging in Go Projects - Part1
• Series: Start with Logging in Go Projects - Part2
• How to collect, standardize, and centralize Golang logs
• Logrus complete tutorial example
• Testing Log Output in Go with logrus
• Logging Handle web Using Logrus
• 4 tips for logging on GCP using golang and logrus

[mtchuyen]

Hook in Logrus

• Channel hook
• Syslog hook
• Database hook
• Kafka hook

[mtchuyen]

Log format sample:

1. logrus.WithFields & logrus.Fields

    cl := logrus.WithFields(
        logrus.Fields{
            "field_one": "value_one",
        })
    cl = cl.WithFields(
        logrus.Fields{
            "field_two": "value_two",
        })
    cl.Info("hello_world")

INFO[0000] hello_world field_one="value_one" field_two="value_two"

log.WithFields(log.Fields{
    "animal": "walrus",
    "field_one": "value_one",
    "field_two": "value_two",
  }).Info("hello_world")

INFO[0000] hello_world animal=walrus field_one="value_one" field_two="value_two"