lager

lager is an opinionated logging library 🍺

Why?

lager only performs string formatting for log levels that you set. If you only want to log Error messages, you don't need to worry about all of your Trace or Debug strings being (costly) formatted.

Here's how the LogLager compares to log.Logger when you want to only log one level in your program instead of all.

BenchmarkLoggerOneAndAllLevels	  200000	      7842 ns/op	     605 B/op	      30 allocs/op
BenchmarkLogLagerOneLevel	 1000000	      2258 ns/op	     250 B/op	      15 allocs/op
BenchmarkLogLagerAllLevel	  200000	      7964 ns/op	     602 B/op	      35 allocs/op

Usage

The main interface that defines a logger is Lager:

type Lager interface {
	Tracef(msg string, v ...interface{})
	Debugf(msg string, v ...interface{})
	Infof(msg string, v ...interface{})
	Warnf(msg string, v ...interface{})
	Errorf(msg string, v ...interface{})
}

Lager provides logging for five levels: Trace, Debug, Info, Warn, and Error.

Currently, lager provides three Lager implementations:

• LogLager: A performant logger for logging directly to log.Logger
• BasicLager: A basic logger for log messages with customizable output
• ContextLager: A context logger for adding context to log messages with customizable output

Log outputs are defined by Drinker:

type Drinker interface {
	Drink(e interface{}) error
}

Currently, there are two Drinker implementations:

• LogDrinker: logs messages using log.Logger
• JSONDrinker: logs messages using json.Marshal

For more usage, see the tests and benchmarks.