1 # Logrus <img src="http://i.imgur.com/hTeVwmJ.png" width="40" height="40" alt=":walrus:" class="emoji" title=":walrus:"/> [![Build Status](https://travis-ci.org/Sirupsen/logrus.svg?branch=master)](https://travis-ci.org/Sirupsen/logrus) [![GoDoc](https://godoc.org/github.com/Sirupsen/logrus?status.svg)](https://godoc.org/github.com/Sirupsen/logrus)
3 **Seeing weird case-sensitive problems?** See [this
4 issue](https://github.com/sirupsen/logrus/issues/451#issuecomment-264332021).
5 This change has been reverted. I apologize for causing this. I greatly
6 underestimated the impact this would have. Logrus strives for stability and
7 backwards compatibility and failed to provide that.
9 Logrus is a structured logger for Go (golang), completely API compatible with
10 the standard library logger. [Godoc][godoc]. **Please note the Logrus API is not
11 yet stable (pre 1.0). Logrus itself is completely stable and has been used in
12 many large deployments. The core API is unlikely to change much but please
13 version control your Logrus to make sure you aren't fetching latest `master` on
16 Nicely color-coded in development (when a TTY is attached, otherwise just
19 ![Colored](http://i.imgur.com/PY7qMwd.png)
21 With `log.SetFormatter(&log.JSONFormatter{})`, for easy parsing by logstash
25 {"animal":"walrus","level":"info","msg":"A group of walrus emerges from the
26 ocean","size":10,"time":"2014-03-10 19:57:38.562264131 -0400 EDT"}
28 {"level":"warning","msg":"The group's number increased tremendously!",
29 "number":122,"omg":true,"time":"2014-03-10 19:57:38.562471297 -0400 EDT"}
31 {"animal":"walrus","level":"info","msg":"A giant walrus appears!",
32 "size":10,"time":"2014-03-10 19:57:38.562500591 -0400 EDT"}
34 {"animal":"walrus","level":"info","msg":"Tremendously sized cow enters the ocean.",
35 "size":9,"time":"2014-03-10 19:57:38.562527896 -0400 EDT"}
37 {"level":"fatal","msg":"The ice breaks!","number":100,"omg":true,
38 "time":"2014-03-10 19:57:38.562543128 -0400 EDT"}
41 With the default `log.SetFormatter(&log.TextFormatter{})` when a TTY is not
42 attached, the output is compatible with the
43 [logfmt](http://godoc.org/github.com/kr/logfmt) format:
46 time="2015-03-26T01:27:38-04:00" level=debug msg="Started observing beach" animal=walrus number=8
47 time="2015-03-26T01:27:38-04:00" level=info msg="A group of walrus emerges from the ocean" animal=walrus size=10
48 time="2015-03-26T01:27:38-04:00" level=warning msg="The group's number increased tremendously!" number=122 omg=true
49 time="2015-03-26T01:27:38-04:00" level=debug msg="Temperature changes" temperature=-4
50 time="2015-03-26T01:27:38-04:00" level=panic msg="It's over 9000!" animal=orca size=9009
51 time="2015-03-26T01:27:38-04:00" level=fatal msg="The ice breaks!" err=&{0x2082280c0 map[animal:orca size:9009] 2015-03-26 01:27:38.441574009 -0400 EDT panic It's over 9000!} number=100 omg=true
57 The simplest way to use Logrus is simply the package-level exported logger:
63 log "github.com/Sirupsen/logrus"
67 log.WithFields(log.Fields{
69 }).Info("A walrus appears")
73 Note that it's completely api-compatible with the stdlib logger, so you can
74 replace your `log` imports everywhere with `log "github.com/Sirupsen/logrus"`
75 and you'll now have the flexibility of Logrus. You can customize it all you
83 log "github.com/Sirupsen/logrus"
87 // Log as JSON instead of the default ASCII formatter.
88 log.SetFormatter(&log.JSONFormatter{})
90 // Output to stdout instead of the default stderr
91 // Can be any io.Writer, see below for File example
92 log.SetOutput(os.Stdout)
94 // Only log the warning severity or above.
95 log.SetLevel(log.WarnLevel)
99 log.WithFields(log.Fields{
102 }).Info("A group of walrus emerges from the ocean")
104 log.WithFields(log.Fields{
107 }).Warn("The group's number increased tremendously!")
109 log.WithFields(log.Fields{
112 }).Fatal("The ice breaks!")
114 // A common pattern is to re-use fields between logging statements by re-using
115 // the logrus.Entry returned from WithFields()
116 contextLogger := log.WithFields(log.Fields{
117 "common": "this is a common field",
118 "other": "I also should be logged always",
121 contextLogger.Info("I'll be logged with common and other field")
122 contextLogger.Info("Me too")
126 For more advanced usage such as logging to multiple locations from the same
127 application, you can also create an instance of the `logrus` Logger:
133 "github.com/Sirupsen/logrus"
136 // Create a new instance of the logger. You can have any number of instances.
137 var log = logrus.New()
140 // The API for setting attributes is a little different than the package level
141 // exported logger. See Godoc.
144 // You could set this to any `io.Writer` such as a file
145 // file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY, 0666)
149 // log.Info("Failed to log to file, using default stderr")
152 log.WithFields(logrus.Fields{
155 }).Info("A group of walrus emerges from the ocean")
161 Logrus encourages careful, structured logging though logging fields instead of
162 long, unparseable error messages. For example, instead of: `log.Fatalf("Failed
163 to send event %s to topic %s with key %d")`, you should log the much more
167 log.WithFields(log.Fields{
171 }).Fatal("Failed to send event")
174 We've found this API forces you to think about logging in a way that produces
175 much more useful logging messages. We've been in countless situations where just
176 a single added field to a log statement that was already there would've saved us
177 hours. The `WithFields` call is optional.
179 In general, with Logrus using any of the `printf`-family functions should be
180 seen as a hint you should add a field, however, you can still use the
181 `printf`-family functions with Logrus.
185 Often it's helpful to have fields _always_ attached to log statements in an
186 application or parts of one. For example, you may want to always log the
187 `request_id` and `user_ip` in the context of a request. Instead of writing
188 `log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip})` on
189 every line, you can create a `logrus.Entry` to pass around instead:
192 requestLogger := log.WithFields(log.Fields{"request_id": request_id, user_ip: user_ip})
193 requestLogger.Info("something happened on that request") # will log request_id and user_ip
194 requestLogger.Warn("something not great happened")
199 You can add hooks for logging levels. For example to send errors to an exception
200 tracking service on `Error`, `Fatal` and `Panic`, info to StatsD or log to
201 multiple places simultaneously, e.g. syslog.
203 Logrus comes with [built-in hooks](hooks/). Add those, or your custom hook, in
208 log "github.com/Sirupsen/logrus"
209 "gopkg.in/gemnasium/logrus-airbrake-hook.v2" // the package is named "aibrake"
210 logrus_syslog "github.com/Sirupsen/logrus/hooks/syslog"
216 // Use the Airbrake hook to report errors that have Error severity or above to
217 // an exception tracker. You can create custom hooks, see the Hooks section.
218 log.AddHook(airbrake.NewHook(123, "xyz", "production"))
220 hook, err := logrus_syslog.NewSyslogHook("udp", "localhost:514", syslog.LOG_INFO, "")
222 log.Error("Unable to connect to local syslog daemon")
228 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).
230 | Hook | Description |
231 | ----- | ----------- |
232 | [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. |
233 | [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. |
234 | [Amazon Kinesis](https://github.com/evalphobia/logrus_kinesis) | Hook for logging to [Amazon Kinesis](https://aws.amazon.com/kinesis/) |
235 | [Amqp-Hook](https://github.com/vladoatanasov/logrus_amqp) | Hook for logging to Amqp broker (Like RabbitMQ) |
236 | [Bugsnag](https://github.com/Shopify/logrus-bugsnag/blob/master/bugsnag.go) | Send errors to the Bugsnag exception tracking service. |
237 | [DeferPanic](https://github.com/deferpanic/dp-logrus) | Hook for logging to DeferPanic |
238 | [ElasticSearch](https://github.com/sohlich/elogrus) | Hook for logging to ElasticSearch|
239 | [Fluentd](https://github.com/evalphobia/logrus_fluent) | Hook for logging to fluentd |
240 | [Go-Slack](https://github.com/multiplay/go-slack) | Hook for logging to [Slack](https://slack.com) |
241 | [Graylog](https://github.com/gemnasium/logrus-graylog-hook) | Hook for logging to [Graylog](http://graylog2.org/) |
242 | [Hiprus](https://github.com/nubo/hiprus) | Send errors to a channel in hipchat. |
243 | [Honeybadger](https://github.com/agonzalezro/logrus_honeybadger) | Hook for sending exceptions to Honeybadger |
244 | [InfluxDB](https://github.com/Abramovic/logrus_influxdb) | Hook for logging to influxdb |
245 | [Influxus] (http://github.com/vlad-doru/influxus) | Hook for concurrently logging to [InfluxDB] (http://influxdata.com/) |
246 | [Journalhook](https://github.com/wercker/journalhook) | Hook for logging to `systemd-journald` |
247 | [KafkaLogrus](https://github.com/goibibo/KafkaLogrus) | Hook for logging to kafka |
248 | [LFShook](https://github.com/rifflock/lfshook) | Hook for logging to the local filesystem |
249 | [Logentries](https://github.com/jcftang/logentriesrus) | Hook for logging to [Logentries](https://logentries.com/) |
250 | [Logentrus](https://github.com/puddingfactory/logentrus) | Hook for logging to [Logentries](https://logentries.com/) |
251 | [Logmatic.io](https://github.com/logmatic/logmatic-go) | Hook for logging to [Logmatic.io](http://logmatic.io/) |
252 | [Logrusly](https://github.com/sebest/logrusly) | Send logs to [Loggly](https://www.loggly.com/) |
253 | [Logstash](https://github.com/bshuster-repo/logrus-logstash-hook) | Hook for logging to [Logstash](https://www.elastic.co/products/logstash) |
254 | [Mail](https://github.com/zbindenren/logrus_mail) | Hook for sending exceptions via mail |
255 | [Mongodb](https://github.com/weekface/mgorus) | Hook for logging to mongodb |
256 | [NATS-Hook](https://github.com/rybit/nats_logrus_hook) | Hook for logging to [NATS](https://nats.io) |
257 | [Octokit](https://github.com/dorajistyle/logrus-octokit-hook) | Hook for logging to github via octokit |
258 | [Papertrail](https://github.com/polds/logrus-papertrail-hook) | Send errors to the [Papertrail](https://papertrailapp.com) hosted logging service via UDP. |
259 | [PostgreSQL](https://github.com/gemnasium/logrus-postgresql-hook) | Send logs to [PostgreSQL](http://postgresql.org) |
260 | [Pushover](https://github.com/toorop/logrus_pushover) | Send error via [Pushover](https://pushover.net) |
261 | [Raygun](https://github.com/squirkle/logrus-raygun-hook) | Hook for logging to [Raygun.io](http://raygun.io/) |
262 | [Redis-Hook](https://github.com/rogierlommers/logrus-redis-hook) | Hook for logging to a ELK stack (through Redis) |
263 | [Rollrus](https://github.com/heroku/rollrus) | Hook for sending errors to rollbar |
264 | [Scribe](https://github.com/sagar8192/logrus-scribe-hook) | Hook for logging to [Scribe](https://github.com/facebookarchive/scribe)|
265 | [Sentry](https://github.com/evalphobia/logrus_sentry) | Send errors to the Sentry error logging and aggregation service. |
266 | [Slackrus](https://github.com/johntdyer/slackrus) | Hook for Slack chat. |
267 | [Stackdriver](https://github.com/knq/sdhook) | Hook for logging to [Google Stackdriver](https://cloud.google.com/logging/) |
268 | [Sumorus](https://github.com/doublefree/sumorus) | Hook for logging to [SumoLogic](https://www.sumologic.com/)|
269 | [Syslog](https://github.com/Sirupsen/logrus/blob/master/hooks/syslog/syslog.go) | Send errors to remote syslog server. Uses standard library `log/syslog` behind the scenes. |
270 | [TraceView](https://github.com/evalphobia/logrus_appneta) | Hook for logging to [AppNeta TraceView](https://www.appneta.com/products/traceview/) |
271 | [Typetalk](https://github.com/dragon3/logrus-typetalk-hook) | Hook for logging to [Typetalk](https://www.typetalk.in/) |
272 | [logz.io](https://github.com/ripcurld00d/logrus-logzio-hook) | Hook for logging to [logz.io](https://logz.io), a Log as a Service using Logstash |
276 Logrus has six logging levels: Debug, Info, Warning, Error, Fatal and Panic.
279 log.Debug("Useful debugging information.")
280 log.Info("Something noteworthy happened!")
281 log.Warn("You should probably take a look at this.")
282 log.Error("Something failed but I'm not quitting.")
283 // Calls os.Exit(1) after logging
285 // Calls panic() after logging
286 log.Panic("I'm bailing.")
289 You can set the logging level on a `Logger`, then it will only log entries with
290 that severity or anything above it:
293 // Will log anything that is info or above (warn, error, fatal, panic). Default.
294 log.SetLevel(log.InfoLevel)
297 It may be useful to set `log.Level = logrus.DebugLevel` in a debug or verbose
298 environment if your application has that.
302 Besides the fields added with `WithField` or `WithFields` some fields are
303 automatically added to all logging events:
305 1. `time`. The timestamp when the entry was created.
306 2. `msg`. The logging message passed to `{Info,Warn,Error,Fatal,Panic}` after
307 the `AddFields` call. E.g. `Failed to send event.`
308 3. `level`. The logging level. E.g. `info`.
312 Logrus has no notion of environment.
314 If you wish for hooks and formatters to only be used in specific environments,
315 you should handle that yourself. For example, if your application has a global
316 variable `Environment`, which is a string representation of the environment you
321 log "github.com/Sirupsen/logrus"
325 // do something here to set environment depending on an environment variable
326 // or command-line flag
327 if Environment == "production" {
328 log.SetFormatter(&log.JSONFormatter{})
330 // The TextFormatter is default, you don't actually have to do this.
331 log.SetFormatter(&log.TextFormatter{})
336 This configuration is how `logrus` was intended to be used, but JSON in
337 production is mostly only useful if you do log aggregation with tools like
342 The built-in logging formatters are:
344 * `logrus.TextFormatter`. Logs the event in colors if stdout is a tty, otherwise
346 * *Note:* to force colored output when there is no TTY, set the `ForceColors`
347 field to `true`. To force no colored output even if there is a TTY set the
348 `DisableColors` field to `true`. For Windows, see
349 [github.com/mattn/go-colorable](https://github.com/mattn/go-colorable).
350 * All options are listed in the [generated docs](https://godoc.org/github.com/sirupsen/logrus#TextFormatter).
351 * `logrus.JSONFormatter`. Logs fields as JSON.
352 * All options are listed in the [generated docs](https://godoc.org/github.com/sirupsen/logrus#JSONFormatter).
354 Third party logging formatters:
356 * [`logstash`](https://github.com/bshuster-repo/logrus-logstash-hook). Logs fields as [Logstash](http://logstash.net) Events.
357 * [`prefixed`](https://github.com/x-cray/logrus-prefixed-formatter). Displays log entry source along with alternative layout.
358 * [`zalgo`](https://github.com/aybabtme/logzalgo). Invoking the P͉̫o̳̼̊w̖͈̰͎e̬͔̭͂r͚̼̹̲ ̫͓͉̳͈ō̠͕͖̚f̝͍̠ ͕̲̞͖͑Z̖̫̤̫ͪa͉̬͈̗l͖͎g̳̥o̰̥̅!̣͔̲̻͊̄ ̙̘̦̹̦.
360 You can define your formatter by implementing the `Formatter` interface,
361 requiring a `Format` method. `Format` takes an `*Entry`. `entry.Data` is a
362 `Fields` type (`map[string]interface{}`) with all your fields as well as the
363 default ones (see Entries section above):
366 type MyJSONFormatter struct {
369 log.SetFormatter(new(MyJSONFormatter))
371 func (f *MyJSONFormatter) Format(entry *Entry) ([]byte, error) {
372 // Note this doesn't include Time, Level and Message which are available on
373 // the Entry. Consult `godoc` on information about those fields or read the
374 // source of the official loggers.
375 serialized, err := json.Marshal(entry.Data)
377 return nil, fmt.Errorf("Failed to marshal fields to JSON, %v", err)
379 return append(serialized, '\n'), nil
383 #### Logger as an `io.Writer`
385 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.
392 // create a stdlib log.Logger that writes to
394 ErrorLog: log.New(w, "", 0),
398 Each line written to that writer will be printed the usual way, using formatters
399 and hooks. The level for those entries is `info`.
401 This means that we can override the standard library logger easily:
404 logger := logrus.New()
405 logger.Formatter = &logrus.JSONFormatter{}
407 // Use logrus for standard log output
408 // Note that `log` here references stdlib's log
409 // Not logrus imported under the name `log`.
410 log.SetOutput(logger.Writer())
415 Log rotation is not provided with Logrus. Log rotation should be done by an
416 external program (like `logrotate(8)`) that can compress and delete old log
417 entries. It should not be a feature of the application-level logger.
421 | Tool | Description |
422 | ---- | ----------- |
423 |[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.|
424 |[Logrus Viper Helper](https://github.com/heirko/go-contrib/tree/master/logrusHelper)|An Helper arround 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) |
428 Logrus has a built in facility for asserting the presence of log messages. This is implemented through the `test` hook and provides:
430 * decorators for existing logger (`test.NewLocal` and `test.NewGlobal`) which basically just add the `test` hook
431 * a test logger (`test.NewNullLogger`) that just records log messages (and does not output any):
434 logger, hook := NewNullLogger()
435 logger.Error("Hello error")
437 assert.Equal(1, len(hook.Entries))
438 assert.Equal(logrus.ErrorLevel, hook.LastEntry().Level)
439 assert.Equal("Hello error", hook.LastEntry().Message)
442 assert.Nil(hook.LastEntry())
447 Logrus can register one or more functions that will be called when any `fatal`
448 level message is logged. The registered handlers will be executed before
449 logrus performs a `os.Exit(1)`. This behavior may be helpful if callers need
450 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.
455 // gracefully shutdown something...
457 logrus.RegisterExitHandler(handler)
463 By default Logger is protected by mutex for concurrent writes, this mutex is invoked when calling hooks and writing logs.
464 If you are sure such locking is not needed, you can call logger.SetNoLock() to disable the locking.
466 Situation when locking is not needed includes:
468 * You have no hooks registered, or hooks calling is already thread-safe.
470 * Writing to logger.Out is already thread-safe, for example:
472 1) logger.Out is protected by locks.
474 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)
476 (Refer to http://www.notthewizard.com/2014/06/17/are-files-appends-really-atomic/)