slog

A simple log lib, support log level.

Features:

Package categorized logger
Support log level
Configured via json

Requires

Only go standard libs

Usage

Get a logger for your package

Assume there are there packages: github.com/kuun/slog/demo, github.com/kuun/slog/demo/pkga, github.com/kuun/slog/demo/pkgb, structured as bellow:

src/github.com/kuun/slog/demo
|-- main.go
|-- pkga
|   `-- a.go
`-- pkgb
    `-- b.go

src/github.com/kuun/slog/demo/main.go

package main

import (
	"github.com/kuun/slog/demo/pkga"
	"github.com/kuun/slog/demo/pkgb"

	"github.com/kuun/slog"
)

var log = slog.GetLogger()

func main() {
	log.Debug("hello slog")
	pkga.Hello()
	pkgb.Hello()
	slog.Close()
}

src/github.com/kuun/slog/demo/pkga/a.go

package pkga

import "github.com/kuun/slog"

var log = slog.GetLogger()

func Hello() {
	log.Debug("hello pkga")
}

src/github.com/kuun/slog/demo/pkgb/b.go

package pkgb

import "github.com/kuun/slog"

var log = slog.GetLogger()

func Hello() {
	log.Debug("hello pkgb")
}

then build and run the app, outputs on the terminal:

D 0601 09:26:19.881703 g/k/s/demo/main.go:12] hello slog
D 0601 09:26:19.881768 g/k/s/d/pkga/a.go:8] hello pkga
D 0601 09:26:19.881770 g/k/s/d/pkgb/b.go:8] hello pkgb

Get a new logger by calling slog.GetLogger, slog will create a slog.Logger categorized by current package, if called more than once in the same package, slog will return the same slog.Logger.

Configure slog

Slog configure file a json object. If there is not configure file or configure file is empty, slog uses the default configure:

{
    "loggers": [
        {
            "pattern": "*",
            "level": "DEBUG",
            "writers": ["STDOUT"]
        }
    ]
}

Now we want to write log to a file, we can modify the configuration like bellow:

{
    "writers": [
        {
            "name": "FILE",
            "file": "/tmp/app.log"
        }
    ],
    "loggers": [
        {
            "pattern": "*",
            "level": "DEBUG",
            "writers": ["FILE", "STDOUT"]
        }
    ]
}

Then save configuration to slog.json.

Then modify environment SLOG_CONF_FILE and run the application:

export SLOG_CONF_FILE=slog.json
./test

Logs will be outputed to stdout and /tmp/app.log

Configure slog

How to specific log configuration file

Slog parse environment value 'SLOG_CONF_FILE' at application startups.

Configuration spec

writers

writers is an array, collects all available writers. There are two predefined writer: "STDOUT", "STDERR".
- writers.name
  
  Writer's name, must be unique.
- writers.file
  
  The file where writer writes to
loggers

loggers is an array, collects all logger configuration
- loggers.pattern
  
  The current configuration's match pattern, the first and last character can be '*' to wildcard multi packages.
- loggers.level
  
  log level of loggers matched by the pattern.
- loggers.writers
  
  writers of loggers matched by the pattern.