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+# Logrus <img src="http://i.imgur.com/hTeVwmJ.png" width="40" height="40" alt=":walrus:" class="emoji" title=":walrus:"/> [](https://github.com/sirupsen/logrus/actions?query=workflow%3ACI) [](https://travis-ci.org/sirupsen/logrus) [](https://pkg.go.dev/github.com/sirupsen/logrus)
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+
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+Logrus is a structured logger for Go (golang), completely API compatible with
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+the standard library logger.
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+
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+**Logrus is in maintenance-mode.** We will not be introducing new features. It's
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+simply too hard to do in a way that won't break many people's projects, which is
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+the last thing you want from your Logging library (again...).
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+
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+This does not mean Logrus is dead. Logrus will continue to be maintained for
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+security, (backwards compatible) bug fixes, and performance (where we are
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+limited by the interface).
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+
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+I believe Logrus' biggest contribution is to have played a part in today's
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+widespread use of structured logging in Golang. There doesn't seem to be a
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+reason to do a major, breaking iteration into Logrus V2, since the fantastic Go
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+community has built those independently. Many fantastic alternatives have sprung
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+up. Logrus would look like those, had it been re-designed with what we know
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+about structured logging in Go today. Check out, for example,
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+[Zerolog][zerolog], [Zap][zap], and [Apex][apex].
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+
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+[zerolog]: https://github.com/rs/zerolog
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+[zap]: https://github.com/uber-go/zap
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+[apex]: https://github.com/apex/log
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+
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+**Seeing weird case-sensitive problems?** It's in the past been possible to
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+import Logrus as both upper- and lower-case. Due to the Go package environment,
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+this caused issues in the community and we needed a standard. Some environments
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+experienced problems with the upper-case variant, so the lower-case was decided.
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+Everything using `logrus` will need to use the lower-case:
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+`github.com/sirupsen/logrus`. Any package that isn't, should be changed.
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+
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+To fix Glide, see [these
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+comments](https://github.com/sirupsen/logrus/issues/553#issuecomment-306591437).
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+For an in-depth explanation of the casing issue, see [this
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+comment](https://github.com/sirupsen/logrus/issues/570#issuecomment-313933276).
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+
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+Nicely color-coded in development (when a TTY is attached, otherwise just
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+plain text):
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+
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+
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+
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+With `log.SetFormatter(&log.JSONFormatter{})`, for easy parsing by logstash
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+or Splunk:
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+
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+```text
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+{"animal":"walrus","level":"info","msg":"A group of walrus emerges from the
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+ocean","size":10,"time":"2014-03-10 19:57:38.562264131 -0400 EDT"}
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+
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+{"level":"warning","msg":"The group's number increased tremendously!",
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+"number":122,"omg":true,"time":"2014-03-10 19:57:38.562471297 -0400 EDT"}
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+
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+{"animal":"walrus","level":"info","msg":"A giant walrus appears!",
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+"size":10,"time":"2014-03-10 19:57:38.562500591 -0400 EDT"}
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+
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+{"animal":"walrus","level":"info","msg":"Tremendously sized cow enters the ocean.",
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+"size":9,"time":"2014-03-10 19:57:38.562527896 -0400 EDT"}
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+
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+{"level":"fatal","msg":"The ice breaks!","number":100,"omg":true,
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+"time":"2014-03-10 19:57:38.562543128 -0400 EDT"}
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+```
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+
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+With the default `log.SetFormatter(&log.TextFormatter{})` when a TTY is not
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+attached, the output is compatible with the
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+[logfmt](http://godoc.org/github.com/kr/logfmt) format:
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+
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+```text
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+time="2015-03-26T01:27:38-04:00" level=debug msg="Started observing beach" animal=walrus number=8
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+time="2015-03-26T01:27:38-04:00" level=info msg="A group of walrus emerges from the ocean" animal=walrus size=10
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+time="2015-03-26T01:27:38-04:00" level=warning msg="The group's number increased tremendously!" number=122 omg=true
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+time="2015-03-26T01:27:38-04:00" level=debug msg="Temperature changes" temperature=-4
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+time="2015-03-26T01:27:38-04:00" level=panic msg="It's over 9000!" animal=orca size=9009
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+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
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+```
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+To ensure this behaviour even if a TTY is attached, set your formatter as follows:
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+
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+```go
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+ log.SetFormatter(&log.TextFormatter{
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+ DisableColors: true,
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+ FullTimestamp: true,
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+ })
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+```
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+
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+#### Logging Method Name
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+
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+If you wish to add the calling method as a field, instruct the logger via:
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+```go
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+log.SetReportCaller(true)
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+```
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+This adds the caller as 'method' like so:
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+
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+```json
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+{"animal":"penguin","level":"fatal","method":"github.com/sirupsen/arcticcreatures.migrate","msg":"a penguin swims by",
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+"time":"2014-03-10 19:57:38.562543129 -0400 EDT"}
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+```
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+
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+```text
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+time="2015-03-26T01:27:38-04:00" level=fatal method=github.com/sirupsen/arcticcreatures.migrate msg="a penguin swims by" animal=penguin
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+```
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+Note that this does add measurable overhead - the cost will depend on the version of Go, but is
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+between 20 and 40% in recent tests with 1.6 and 1.7. You can validate this in your
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+environment via benchmarks:
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+```
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+go test -bench=.*CallerTracing
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+```
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+
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+
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+#### Case-sensitivity
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+
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+The organization's name was changed to lower-case--and this will not be changed
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+back. If you are getting import conflicts due to case sensitivity, please use
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+the lower-case import: `github.com/sirupsen/logrus`.
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+
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+#### Example
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+
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+The simplest way to use Logrus is simply the package-level exported logger:
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+
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+```go
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+package main
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+
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+import (
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+ log "github.com/sirupsen/logrus"
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+)
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+
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+func main() {
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+ log.WithFields(log.Fields{
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+ "animal": "walrus",
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+ }).Info("A walrus appears")
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+}
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+```
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+
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+Note that it's completely api-compatible with the stdlib logger, so you can
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+replace your `log` imports everywhere with `log "github.com/sirupsen/logrus"`
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+and you'll now have the flexibility of Logrus. You can customize it all you
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+want:
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+
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+```go
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+package main
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+
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+import (
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+ "os"
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+ log "github.com/sirupsen/logrus"
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+)
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+
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+func init() {
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+ // Log as JSON instead of the default ASCII formatter.
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+ log.SetFormatter(&log.JSONFormatter{})
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+
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+ // Output to stdout instead of the default stderr
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+ // Can be any io.Writer, see below for File example
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+ log.SetOutput(os.Stdout)
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+
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+ // Only log the warning severity or above.
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+ log.SetLevel(log.WarnLevel)
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+}
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+
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+func main() {
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+ log.WithFields(log.Fields{
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+ "animal": "walrus",
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+ "size": 10,
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+ }).Info("A group of walrus emerges from the ocean")
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+
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+ log.WithFields(log.Fields{
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+ "omg": true,
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+ "number": 122,
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+ }).Warn("The group's number increased tremendously!")
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+
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+ log.WithFields(log.Fields{
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+ "omg": true,
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+ "number": 100,
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+ }).Fatal("The ice breaks!")
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+
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+ // A common pattern is to re-use fields between logging statements by re-using
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+ // the logrus.Entry returned from WithFields()
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+ contextLogger := log.WithFields(log.Fields{
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+ "common": "this is a common field",
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+ "other": "I also should be logged always",
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+ })
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+
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+ contextLogger.Info("I'll be logged with common and other field")
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+ contextLogger.Info("Me too")
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+}
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+```
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+
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+For more advanced usage such as logging to multiple locations from the same
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+application, you can also create an instance of the `logrus` Logger:
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+
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+```go
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+package main
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+
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+import (
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+ "os"
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+ "github.com/sirupsen/logrus"
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+)
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+
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+// Create a new instance of the logger. You can have any number of instances.
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+var log = logrus.New()
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+
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+func main() {
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+ // The API for setting attributes is a little different than the package level
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+ // exported logger. See Godoc.
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+ log.Out = os.Stdout
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+
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+ // You could set this to any `io.Writer` such as a file
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+ // file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
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+ // if err == nil {
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+ // log.Out = file
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+ // } else {
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+ // log.Info("Failed to log to file, using default stderr")
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+ // }
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+
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+ log.WithFields(logrus.Fields{
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+ "animal": "walrus",
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+ "size": 10,
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+ }).Info("A group of walrus emerges from the ocean")
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+}
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+```
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+
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+#### Fields
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+
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+Logrus encourages careful, structured logging through logging fields instead of
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+long, unparseable error messages. For example, instead of: `log.Fatalf("Failed
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+to send event %s to topic %s with key %d")`, you should log the much more
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+discoverable:
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+
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+```go
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+log.WithFields(log.Fields{
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+ "event": event,
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+ "topic": topic,
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+ "key": key,
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+}).Fatal("Failed to send event")
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+```
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+
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+We've found this API forces you to think about logging in a way that produces
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+much more useful logging messages. We've been in countless situations where just
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+a single added field to a log statement that was already there would've saved us
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+hours. The `WithFields` call is optional.
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+
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+In general, with Logrus using any of the `printf`-family functions should be
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+seen as a hint you should add a field, however, you can still use the
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+`printf`-family functions with Logrus.
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+
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+#### Default Fields
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+
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+Often it's helpful to have fields _always_ attached to log statements in an
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+application or parts of one. For example, you may want to always log the
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+`request_id` and `user_ip` in the context of a request. Instead of writing
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+`log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip})` on
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+every line, you can create a `logrus.Entry` to pass around instead:
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+
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+```go
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+requestLogger := log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip})
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+requestLogger.Info("something happened on that request") # will log request_id and user_ip
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+requestLogger.Warn("something not great happened")
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+```
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+
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+#### Hooks
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+
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+You can add hooks for logging levels. For example to send errors to an exception
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+tracking service on `Error`, `Fatal` and `Panic`, info to StatsD or log to
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+multiple places simultaneously, e.g. syslog.
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+
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+Logrus comes with [built-in hooks](hooks/). Add those, or your custom hook, in
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+`init`:
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+
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+```go
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+import (
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+ log "github.com/sirupsen/logrus"
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+ "gopkg.in/gemnasium/logrus-airbrake-hook.v2" // the package is named "airbrake"
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+ logrus_syslog "github.com/sirupsen/logrus/hooks/syslog"
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+ "log/syslog"
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+)
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+
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+func init() {
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+
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+ // Use the Airbrake hook to report errors that have Error severity or above to
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+ // an exception tracker. You can create custom hooks, see the Hooks section.
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+ log.AddHook(airbrake.NewHook(123, "xyz", "production"))
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+
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+ hook, err := logrus_syslog.NewSyslogHook("udp", "localhost:514", syslog.LOG_INFO, "")
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+ if err != nil {
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+ log.Error("Unable to connect to local syslog daemon")
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+ } else {
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+ log.AddHook(hook)
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+ }
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+}
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+```
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+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).
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+
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+A list of currently known service hooks can be found in this wiki [page](https://github.com/sirupsen/logrus/wiki/Hooks)
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+
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+
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+#### Level logging
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+
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+Logrus has seven logging levels: Trace, Debug, Info, Warning, Error, Fatal and Panic.
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+
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+```go
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+log.Trace("Something very low level.")
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+log.Debug("Useful debugging information.")
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+log.Info("Something noteworthy happened!")
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+log.Warn("You should probably take a look at this.")
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+log.Error("Something failed but I'm not quitting.")
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+// Calls os.Exit(1) after logging
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+log.Fatal("Bye.")
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+// Calls panic() after logging
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+log.Panic("I'm bailing.")
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+```
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+
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+You can set the logging level on a `Logger`, then it will only log entries with
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+that severity or anything above it:
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+
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+```go
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+// Will log anything that is info or above (warn, error, fatal, panic). Default.
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+log.SetLevel(log.InfoLevel)
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+```
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+
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+It may be useful to set `log.Level = logrus.DebugLevel` in a debug or verbose
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+environment if your application has that.
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+
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+Note: If you want different log levels for global (`log.SetLevel(...)`) and syslog logging, please check the [syslog hook README](hooks/syslog/README.md#different-log-levels-for-local-and-remote-logging).
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+
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+#### Entries
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+
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+Besides the fields added with `WithField` or `WithFields` some fields are
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+automatically added to all logging events:
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+
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+1. `time`. The timestamp when the entry was created.
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+2. `msg`. The logging message passed to `{Info,Warn,Error,Fatal,Panic}` after
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+ the `AddFields` call. E.g. `Failed to send event.`
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+3. `level`. The logging level. E.g. `info`.
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+
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+#### Environments
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+
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+Logrus has no notion of environment.
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+
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+If you wish for hooks and formatters to only be used in specific environments,
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+you should handle that yourself. For example, if your application has a global
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+variable `Environment`, which is a string representation of the environment you
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+could do:
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+
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+```go
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+import (
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+ log "github.com/sirupsen/logrus"
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+)
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+
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+func init() {
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+ // do something here to set environment depending on an environment variable
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+ // or command-line flag
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+ if Environment == "production" {
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+ log.SetFormatter(&log.JSONFormatter{})
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+ } else {
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+ // The TextFormatter is default, you don't actually have to do this.
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+ log.SetFormatter(&log.TextFormatter{})
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+ }
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+}
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+```
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+
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+This configuration is how `logrus` was intended to be used, but JSON in
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+production is mostly only useful if you do log aggregation with tools like
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+Splunk or Logstash.
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+
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+#### Formatters
|
|
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+
|
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+The built-in logging formatters are:
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+
|
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+* `logrus.TextFormatter`. Logs the event in colors if stdout is a tty, otherwise
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+ without colors.
|
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+ * *Note:* to force colored output when there is no TTY, set the `ForceColors`
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+ field to `true`. To force no colored output even if there is a TTY set the
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+ `DisableColors` field to `true`. For Windows, see
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+ [github.com/mattn/go-colorable](https://github.com/mattn/go-colorable).
|
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+ * When colors are enabled, levels are truncated to 4 characters by default. To disable
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+ truncation set the `DisableLevelTruncation` field to `true`.
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+ * When outputting to a TTY, it's often helpful to visually scan down a column where all the levels are the same width. Setting the `PadLevelText` field to `true` enables this behavior, by adding padding to the level text.
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|
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+ * All options are listed in the [generated docs](https://godoc.org/github.com/sirupsen/logrus#TextFormatter).
|
|
|
+* `logrus.JSONFormatter`. Logs fields as JSON.
|
|
|
+ * All options are listed in the [generated docs](https://godoc.org/github.com/sirupsen/logrus#JSONFormatter).
|
|
|
+
|
|
|
+Third party logging formatters:
|
|
|
+
|
|
|
+* [`FluentdFormatter`](https://github.com/joonix/log). Formats entries that can be parsed by Kubernetes and Google Container Engine.
|
|
|
+* [`GELF`](https://github.com/fabienm/go-logrus-formatters). Formats entries so they comply to Graylog's [GELF 1.1 specification](http://docs.graylog.org/en/2.4/pages/gelf.html).
|
|
|
+* [`logstash`](https://github.com/bshuster-repo/logrus-logstash-hook). Logs fields as [Logstash](http://logstash.net) Events.
|
|
|
+* [`prefixed`](https://github.com/x-cray/logrus-prefixed-formatter). Displays log entry source along with alternative layout.
|
|
|
+* [`zalgo`](https://github.com/aybabtme/logzalgo). Invoking the Power of Zalgo.
|
|
|
+* [`nested-logrus-formatter`](https://github.com/antonfisher/nested-logrus-formatter). Converts logrus fields to a nested structure.
|
|
|
+* [`powerful-logrus-formatter`](https://github.com/zput/zxcTool). get fileName, log's line number and the latest function's name when print log; Sava log to files.
|
|
|
+* [`caption-json-formatter`](https://github.com/nolleh/caption_json_formatter). logrus's message json formatter with human-readable caption added.
|
|
|
+
|
|
|
+You can define your formatter by implementing the `Formatter` interface,
|
|
|
+requiring a `Format` method. `Format` takes an `*Entry`. `entry.Data` is a
|
|
|
+`Fields` type (`map[string]interface{}`) with all your fields as well as the
|
|
|
+default ones (see Entries section above):
|
|
|
+
|
|
|
+```go
|
|
|
+type MyJSONFormatter struct {
|
|
|
+}
|
|
|
+
|
|
|
+log.SetFormatter(new(MyJSONFormatter))
|
|
|
+
|
|
|
+func (f *MyJSONFormatter) Format(entry *Entry) ([]byte, error) {
|
|
|
+ // 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, %w", 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 be generated with different configs in different environments.|
|
|
|
+|[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 adds the `test` hook
|
|
|
+* a test logger (`test.NewNullLogger`) that just records log messages (and does not output any):
|
|
|
+
|
|
|
+```go
|
|
|
+import(
|
|
|
+ "github.com/sirupsen/logrus"
|
|
|
+ "github.com/sirupsen/logrus/hooks/test"
|
|
|
+ "github.com/stretchr/testify/assert"
|
|
|
+ "testing"
|
|
|
+)
|
|
|
+
|
|
|
+func TestSomething(t*testing.T){
|
|
|
+ logger, hook := test.NewNullLogger()
|
|
|
+ logger.Error("Helloerror")
|
|
|
+
|
|
|
+ assert.Equal(t, 1, len(hook.Entries))
|
|
|
+ assert.Equal(t, logrus.ErrorLevel, hook.LastEntry().Level)
|
|
|
+ assert.Equal(t, "Helloerror", hook.LastEntry().Message)
|
|
|
+
|
|
|
+ hook.Reset()
|
|
|
+ assert.Nil(t, hook.LastEntry())
|
|
|
+}
|
|
|
+```
|
|
|
+
|
|
|
+#### Fatal handlers
|
|
|
+
|
|
|
+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 an `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 a mutex for concurrent writes. The mutex is held 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 an os.File handler opened with `O_APPEND` flag, and every write is smaller than 4k. (This allows multi-thread/multi-process writing)
|
|
|
+
|
|
|
+ (Refer to http://www.notthewizard.com/2014/06/17/are-files-appends-really-atomic/)
|