Logman

---

Deeply configurable logging library for Go with no configuration required to start

Installation

go get -u github.com/mishankov/logman

Usage

Default logger

For basic log output to stdout, the default logger can be used:

package main

import "github.com/mishankov/logman/loggers"

func main() {
	logger := loggers.NewDefaultLogger()
	logger.Info("Hello, world!")
}

Available logging functions

package main

import (
	"github.com/mishankov/logman"
	"github.com/mishankov/logman/loggers"
)

func main() {
	logger := loggers.NewDefaultLogger()

	logger.Debug("Hello,", "world!")
	logger.Debugf("Hello, %s!", "world")

	logger.Info("Hello,", "world!")
	logger.Infof("Hello, %s!", "world")

	logger.Warn("Hello,", "world!")
	logger.Warnf("Hello, %s!", "world")

	logger.Error("Hello,", "world!")
	logger.Errorf("Hello, %s!", "world")

	logger.Fatal("Hello,", "world!")
	logger.Fatalf("Hello, %s!", "world")

	logger.Log(logman.Info, "Hello,", "world!")
	logger.Logf(logman.Info, "Hello, %s!", "world")
}

Custom logger

You can use logman.NewLogger to create a custom logger. For example, this is how to mimic loggers.NewDefaultLogger using logman.NewLogger:

package main

import (
	"os"
	"github.com/mishankov/logman"
	"github.com/mishankov/logman/formatters"
)

func main() {
	logger := logman.NewLogger(os.Stdout, formatters.NewDefaultFormatter(formatters.DefaultFormat, formatters.DefaultTimeLayout), nil)
}

Writers

Writers output logs to some destination. Every writer should implement the io.Writer interface. Logman provides FileWriter:

package main

import "github.com/mishankov/logman/writers"

func main() {
	fw, _ := writers.NewFileWriter("test.log")
}

DefaultLogger uses os.Stdout as writer.

Formatters

Formatters format log messages before they are passed to the writer. Every formatter should implement the logman.Formatter interface. Logman provides DefaultFormatter and JSONFormatter:

package main

import "github.com/mishankov/logman/formatters"

func main() {
	formatter := formatters.NewDefaultFormatter(formatters.DefaultFormat, formatters.DefaultTimeLayout)
	jsonFormatter := formatters.NewJSONFormatter()
}

Filters

Filters filter log messages. Every filter should implement the logman.Filter interface. Logman provides LevelFilter:

package main

import "github.com/mishankov/logman/filters"

func main() {
	filter := filters.NewLevelFilter(logman.Info)
}

Examples

Let's see how to create a custom logger that outputs Error or higher level messages in JSON format to a file:

package main

import (
	"github.com/mishankov/logman"
	"github.com/mishankov/logman/filters"
	"github.com/mishankov/logman/formatters"
	"github.com/mishankov/logman/writers"
)

func main() {
	fw, _ := writers.NewFileWriter("error.log")
	formatter := formatters.NewJSONFormatter()
	filter := filters.NewLevelFilter(logman.Error)
	logger := logman.NewLogger(fw, formatter, filter)

	logger.Error("Hello,", "world!")
	logger.Debug("I am not logged")
}

Motivation

• Practice Golang and TDD skills
• Simple but flexible logging for personal projects