go-log/README.md

go-log
================

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Logging package similar to log4j for the Golang.

- Support dynamic log level
- Support customized formatter
  - TextFormatter
  - JSONFormatter
- Support multiple rolling file writers
  - FixedSizeFileWriter
  - DailyFileWriter
  - AlwaysNewFileWriter

Installation
---------------

```bash
$ go get github.com/subchen/go-log
```

Usage
---------------

```go
package main

import (
    "os"
    "errors"
    "github.com/subchen/go-log"
)

func main() {
    log.Debugf("app = %s", os.Args[0])
    log.Errorf("error = %v", errors.New("some error"))

    // dynamic set level
    log.Default.Level = log.DEBUG

    log.Debug("cannot output debug message")
    log.Infoln("can output info message")
}
```

### Output

Default log to console, you can set `Logger.Out` to set a file writer into log.

```go
import (
    "github.com/subchen/go-log"
    "github.com/subchen/go-log/writers"
)

log.Default.Out = &writers.FixedSizeFileWriter{
    Name:     "/tmp/test.log",
    MaxSize:  10 * 1024 * 1024, // 10m
    MaxCount: 10,
})
```

Three builtin writers for use

```go
// Create log file if file size large than fixed size (10m)
// files: /tmp/test.log.0 .. test.log.10
&writers.FixedSizeFileWriter{
    Name:     "/tmp/test.log",
    MaxSize:  10 * 1024 * 1024, // 10m
    MaxCount: 10,
}

// Create log file every day.
// files: /tmp/test.log.20160102
&writers.DailyFileWriter{
    Name: "/tmp/test.log",
    MaxCount: 10,
}

// Create log file every process.
// files: /tmp/test.log.20160102_150405
&writers.AlwaysNewFileWriter{
    Name: "/tmp/test.log",
    MaxCount: 10,
}

// Output to multiple writes
io.MultiWriter(
    os.Stdout,
    &writers.DailyFileWriter{
        Name: "/tmp/test.log",
        MaxCount: 10,
    }
    //...
)
```

### Formatter

```go
import (
    "github.com/subchen/go-log"
    "github.com/subchen/go-log/formatters"
)

log.Default.Formatter = new(formatters.TextFormatter)
```


### New Logger instance

```go
import (
    "github.com/subchen/go-log"
)

func main() {
    logger := &log.Logger{
		Level:     log.INFO,
		Formatter: new(formatters.JSONFormatter),
		Out:       os.Stdout,
	}

    logger.Infof("i = %d", 99)
}
```

## LICENSE

Apache 2.0