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https://github.com/ian-kent/go-log

A logger, for Go
https://github.com/ian-kent/go-log

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A logger, for Go

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Go-Log

======



[![Build Status](https://travis-ci.org/ian-kent/go-log.svg?branch=master)](https://travis-ci.org/ian-kent/go-log)



A logger, for Go!



It's sort of ```log``` and ```code.google.com/p/log4go``` compatible, so in most cases

can be used without any code changes.



#### Breaking change



go-log was inconsistent with the default Go 'log' package, and log.Fatal calls didn't trigger an os.Exit(1).



This has been fixed in the current release of go-log, which might break backwards compatibility.



You can disable the fix by setting ExitOnFatal to false, e.g.



    log.Logger().ExitOnFatal = false



### Getting started



Install go-log:



```

go get github.com/ian-kent/go-log/log

```



Use the logger in your application:



```

import(

  "github.com/ian-kent/go-log/log"

)



// Pass a log message and arguments directly

log.Debug("Example log message: %s", "example arg")



// Pass a function which returns a log message and arguments

log.Debug(func(){[]interface{}{"Example log message: %s", "example arg"}})

log.Debug(func(i ...interface{}){[]interface{}{"Example log message: %s", "example arg"}})

```



You can also get the logger instance:

```

logger := log.Logger()

logger.Debug("Yey!")

```



Or get a named logger instance:



```

logger := log.Logger("foo.bar")

```



### Log levels



The default log level is DEBUG.



To get the current log level:



```

level := logger.Level()

```



Or to set the log level:



```

// From a LogLevel

logger.SetLevel(levels.TRACE)



// From a string

logger.SetLevel(log.Stol("TRACE"))

```



### Log appenders



The default log appender is ```appenders.Console()```, which logs

the raw message to STDOUT.



To get the current log appender:



```

appender := logger.Appender()

```



If the appender is ```nil```, the parent loggers appender will be used

instead.



If the appender eventually resolves to ```nil```, log data will be

silently dropped.



You can set the log appender:



```

logger.SetAppender(appenders.Console())

```



#### Rolling file appender



Similar to log4j's rolling file appender, you can use



```

// Append to (or create) file

logger.SetAppender(appenders.RollingFile("filename.log", true))



// Truncate (or create) file

logger.SetAppender(appenders.RollingFile("filename.log", false))

```



You can also control the number of log files which are kept:

```

r := appenders.RollingFile("filename.log", true)

r.MaxBackupIndex = 2 // filename.log, filename.log.1, filename.log.2

```



And the maximum log file size (in bytes):

```

r := appenders.RollingFile("filename.log", true)

r.MaxFileSize = 1024 // 1KB, defaults to 100MB

```



#### Fluentd appender



The fluentd appender lets you write log data directly to fluentd:



```

logger.SetAppender(appenders.Fluentd(fluent.Config{}))

```



It uses ```github.com/t-k/fluent-logger-golang```.



The tag is currently fixed to 'go-log', and the data structure sent

to fluentd is simple:



```

{

  message: ""

}



```



### Layouts



Each appender has its own layout. This allows the log data to be transformed

as it is written to the appender.



The default layout is ```layout.Basic()```, which passes the log message

and its arguments through ```fmt.Sprintf```.



To get the current log appender layout:

```

appender := logger.Appender()

layout := appender.Layout()

```



To set the log appender layout:

```

appender.SetLayout(layout.Basic())

```



You can also use ```layout.Pattern(pattern string)```, which accepts a

pattern format similar to log4j:



| Code | Description

| ---- | -----------

| %c   | The package the log statement is in

| %C   | Currently also the package the log statement is in

| %d   | The current date/time, using ```time.Now().String()```

| %F   | The filename the log statement is in

| %l   | The location of the log statement, e.g. ```package/somefile.go:12```

| %L   | The line number the log statement is on

| %m   | The log message and its arguments formatted with ```fmt.Sprintf```

| %n   | A new-line character

| %p   | Priority - the log level

| %r   | ms since logger was created



### Logger inheritance



Loggers are namespaced with a ```.```, following similar rules to Log4j.



If you create a logger named ```foo```, it will automatically inherit the

log settings (levels and appender) of the root logger.



If you then create a logger named ```foo.bar```, it will inherit the log

settings of ```foo```, which in turn inherits the log settings from the

root logger.



You can break this by setting the log level or setting an appender on

a child logger, e.g.:



```

logger := log.Logger("foo.bar")

logger.SetLevel(levels.TRACE)

logger.SetAppender(appenders.Console())

```



If you then created a logger named ```foo.bar.qux```, it would inherit

the trace level and console appender of the ```foo.bar``` logger.



### Roadmap



* log4j configuration support

  * .properties

  * .xml

  * .json

* layouts

  * fixmes/todos in pattern layout

* appenders

  * add socket appender

  * fixmes/todos and tests for fluentd appender

* optimise logger creation

  * collapse loggers when parent namespace is unused

  * reorganise loggers when new child tree is created

* add godoc documentation



### Contributing



Before submitting a pull request:



  * Format your code: ```go fmt ./...```

  * Make sure tests pass: ```go test ./...```



### Licence



Copyright ©‎ 2014, Ian Kent (http://www.iankent.eu).



Released under MIT license, see [LICENSE](LICENSE.md) for details.