log.Error("Unable to connect to local syslog daemon")
} else {
log.AddHook(hook)
}
}
```
Note: Syslog hook also support connecting to local syslog (Ex. "/dev/log" or "/var/run/syslog" or "/var/run/log"). For the detail, please check the [syslog hook README](hooks/syslog/README.md).
| Hook | Description |
| ----- | ----------- |
| [Airbrake "legacy"](https://github.com/gemnasium/logrus-airbrake-legacy-hook) | Send errors to an exception tracking service compatible with the Airbrake API V2. Uses [`airbrake-go`](https://github.com/tobi/airbrake-go) behind the scenes. |
| [Airbrake](https://github.com/gemnasium/logrus-airbrake-hook) | Send errors to the Airbrake API V3. Uses the official [`gobrake`](https://github.com/airbrake/gobrake) behind the scenes. |
| [Amazon Kinesis](https://github.com/evalphobia/logrus_kinesis) | Hook for logging to [Amazon Kinesis](https://aws.amazon.com/kinesis/) |
| [Amqp-Hook](https://github.com/vladoatanasov/logrus_amqp) | Hook for logging to Amqp broker (Like RabbitMQ) |
| [Application Insights](https://github.com/jjcollinge/logrus-appinsights) | Hook for logging to [Application Insights](https://azure.microsoft.com/en-us/services/application-insights/)
| [Logentries](https://github.com/jcftang/logentriesrus) | Hook for logging to [Logentries](https://logentries.com/) |
| [Logentrus](https://github.com/puddingfactory/logentrus) | Hook for logging to [Logentries](https://logentries.com/) |
| [Logmatic.io](https://github.com/logmatic/logmatic-go) | Hook for logging to [Logmatic.io](http://logmatic.io/) |
| [Logrusly](https://github.com/sebest/logrusly) | Send logs to [Loggly](https://www.loggly.com/) |
| [Logstash](https://github.com/bshuster-repo/logrus-logstash-hook) | Hook for logging to [Logstash](https://www.elastic.co/products/logstash) |
| [Mail](https://github.com/zbindenren/logrus_mail) | Hook for sending exceptions via mail |
| [Mattermost](https://github.com/shuLhan/mattermost-integration/tree/master/hooks/logrus) | Hook for logging to [Mattermost](https://mattermost.com/) |
| [Mongodb](https://github.com/weekface/mgorus) | Hook for logging to mongodb |
| [NATS-Hook](https://github.com/rybit/nats_logrus_hook) | Hook for logging to [NATS](https://nats.io) |
| [Octokit](https://github.com/dorajistyle/logrus-octokit-hook) | Hook for logging to github via octokit |
| [Papertrail](https://github.com/polds/logrus-papertrail-hook) | Send errors to the [Papertrail](https://papertrailapp.com) hosted logging service via UDP. |
| [PostgreSQL](https://github.com/gemnasium/logrus-postgresql-hook) | Send logs to [PostgreSQL](http://postgresql.org) |
// Note this doesn't include Time, Level and Message which are available on
// the Entry. Consult `godoc` on information about those fields or read the
// source of the official loggers.
serialized, err := json.Marshal(entry.Data)
if err != nil {
return nil, fmt.Errorf("Failed to marshal fields to JSON, %v", err)
}
return append(serialized, '\n'), nil
}
```
#### Logger as an `io.Writer`
Logrus can be transformed into an `io.Writer`. That writer is the end of an `io.Pipe` and it is your responsibility to close it.
```go
w := logger.Writer()
defer w.Close()
srv := http.Server{
// create a stdlib log.Logger that writes to
// logrus.Logger.
ErrorLog: log.New(w, "", 0),
}
```
Each line written to that writer will be printed the usual way, using formatters
and hooks. The level for those entries is `info`.
This means that we can override the standard library logger easily:
```go
logger := logrus.New()
logger.Formatter = &logrus.JSONFormatter{}
// Use logrus for standard log output
// Note that `log` here references stdlib's log
// Not logrus imported under the name `log`.
log.SetOutput(logger.Writer())
```
#### Rotation
Log rotation is not provided with Logrus. Log rotation should be done by an
external program (like `logrotate(8)`) that can compress and delete old log
entries. It should not be a feature of the application-level logger.
#### Tools
| Tool | Description |
| ---- | ----------- |
|[Logrus Mate](https://github.com/gogap/logrus_mate)|Logrus mate is a tool for Logrus to manage loggers, you can initial logger's level, hook and formatter by config file, the logger will generated with different config at different environment.|
|[Logrus Viper Helper](https://github.com/heirko/go-contrib/tree/master/logrusHelper)|An Helper around Logrus to wrap with spf13/Viper to load configuration with fangs! And to simplify Logrus configuration use some behavior of [Logrus Mate](https://github.com/gogap/logrus_mate). [sample](https://github.com/heirko/iris-contrib/blob/master/middleware/logrus-logger/example) |
#### Testing
Logrus has a built in facility for asserting the presence of log messages. This is implemented through the `test` hook and provides:
* decorators for existing logger (`test.NewLocal` and `test.NewGlobal`) which basically just add the `test` hook
* a test logger (`test.NewNullLogger`) that just records log messages (and does not output any):
Logrus can register one or more functions that will be called when any `fatal`
level message is logged. The registered handlers will be executed before
logrus performs a `os.Exit(1)`. This behavior may be helpful if callers need
to gracefully shutdown. Unlike a `panic("Something went wrong...")` call which can be intercepted with a deferred `recover` a call to `os.Exit(1)` can not be intercepted.
```
...
handler := func() {
// gracefully shutdown something...
}
logrus.RegisterExitHandler(handler)
...
```
#### Thread safety
By default Logger is protected by mutex for concurrent writes, this mutex is invoked when calling hooks and writing logs.
If you are sure such locking is not needed, you can call logger.SetNoLock() to disable the locking.
Situation when locking is not needed includes:
* You have no hooks registered, or hooks calling is already thread-safe.
* Writing to logger.Out is already thread-safe, for example:
1) logger.Out is protected by locks.
2) logger.Out is a os.File handler opened with `O_APPEND` flag, and every write is smaller than 4k. (This allow multi-thread/multi-process writing)
(Refer to http://www.notthewizard.com/2014/06/17/are-files-appends-really-atomic/)
