Log

Logging is an important part of the application and having a consistent logging mechanism and structure is mandatory. With several teams writing different components that talk to each other, being able to read each others logs could be the difference between finding bugs quickly or wasting hours.

License

This software is licensed under the Apache license. For full text see LICENSE

Examples

The following code provides some examples of logging.

Logging Without Log Levels

func main() {
	var buf bytes.Buffer
	log.Init("LogExample", 0, log.DevWriter{Device: log.DevAll, Writer: &buf})

	Square(5)

	log.Shutdown()
	fmt.Printf(buf.String())
}

func Square(n int) int {
	context := "SquareTwice"
	function := "Square"

	log.Start(context, function)

	sq := n * n
	log.Warnf(context, function, "Square 1: %d\n", sq)

	sq = 0
	for i := 0; i < n; i++ {
		sq += n
	}
	log.Tracef(context, function, "Square 2: %d\n", sq)

	log.Complete(context, function)

	return sq
}

The output produced

2016/08/22 13:05:42.596: LogExample[29218]: main.go#24: SquareTwice: Square: Started:
2016/08/22 13:05:42.596: LogExample[29218]: main.go#27: SquareTwice: Square: Warning: Square 1: 25
2016/08/22 13:05:42.596: LogExample[29218]: main.go#33: SquareTwice: Square: Trace: Square 2: 25
2016/08/22 13:05:42.596: LogExample[29218]: main.go#35: SquareTwice: Square: Completed:

Logging With Log Levels

var warnLogger = log.NewLogger("squareLogger", func() int { return log.LevelWarning })

func main() {
	var buf bytes.Buffer
	log.Init("LogExample", 0, log.DevWriter{Device: log.DevAll, Writer: &buf})

	Square(5)

	log.Shutdown()
	fmt.Printf(buf.String())
}

func Square(n int) int {
	context := "SquareTwice"
	function := "Square"

	log.Start(context, function)

	sq := n * n
	warnLogger.Warnf(context, function, "Square 1: %d\n", sq)

	sq = 0
	for i := 0; i < n; i++ {
		sq += n
	}
	// NOTE: The following TRACE line will not be emitted because the log level
	// of the `warnLogger` is at the `Warning` level.
	warnLogger.Tracef(context, function, "Square 2: %d\n", sq)

	log.Complete(context, function)

	return sq
}

The output produced

2016/08/22 13:20:41.594: LogExample[29406]: main.go#26: SquareTwice: Square: Started:
2016/08/22 13:20:41.594: LogExample[29406]: main.go#29: SquareTwice: Square: Warning: Square 1: 25
2016/08/22 13:20:41.594: LogExample[29406]: main.go#37: SquareTwice: Square: Completed:

Project Info

Package docs: https://godoc.org/github.com/Comcast/go-log/log