logrus

package module
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 Go to latest Published: Apr 3, 2019 License: MIT Imports: 16 Imported by: 0

README

Logrus  Build Status GoDoc

Logrus is a structured logger for Go (golang), completely API compatible with the standard library logger.

Seeing weird case-sensitive problems? It's in the past been possible to import Logrus as both upper- and lower-case. Due to the Go package environment, this caused issues in the community and we needed a standard. Some environments experienced problems with the upper-case variant, so the lower-case was decided. Everything using logrus will need to use the lower-case: github.com/hrxu01/logrus. Any package that isn't, should be changed.

To fix Glide, see these comments. For an in-depth explanation of the casing issue, see this comment.

Are you interested in assisting in maintaining Logrus? Currently I have a lot of obligations, and I am unable to provide Logrus with the maintainership it needs. If you'd like to help, please reach out to me at simon at author's username dot com.

Nicely color-coded in development (when a TTY is attached, otherwise just plain text):

Colored

With log.SetFormatter(&log.JSONFormatter{}), for easy parsing by logstash or Splunk:

{"animal":"walrus","level":"info","msg":"A group of walrus emerges from the
ocean","size":10,"time":"2014-03-10 19:57:38.562264131 -0400 EDT"}

{"level":"warning","msg":"The group's number increased tremendously!",
"number":122,"omg":true,"time":"2014-03-10 19:57:38.562471297 -0400 EDT"}

{"animal":"walrus","level":"info","msg":"A giant walrus appears!",
"size":10,"time":"2014-03-10 19:57:38.562500591 -0400 EDT"}

{"animal":"walrus","level":"info","msg":"Tremendously sized cow enters the ocean.",
"size":9,"time":"2014-03-10 19:57:38.562527896 -0400 EDT"}

{"level":"fatal","msg":"The ice breaks!","number":100,"omg":true,
"time":"2014-03-10 19:57:38.562543128 -0400 EDT"}

With the default log.SetFormatter(&log.TextFormatter{}) when a TTY is not attached, the output is compatible with the logfmt format:

time="2015-03-26T01:27:38-04:00" level=debug msg="Started observing beach" animal=walrus number=8
time="2015-03-26T01:27:38-04:00" level=info msg="A group of walrus emerges from the ocean" animal=walrus size=10
time="2015-03-26T01:27:38-04:00" level=warning msg="The group's number increased tremendously!" number=122 omg=true
time="2015-03-26T01:27:38-04:00" level=debug msg="Temperature changes" temperature=-4
time="2015-03-26T01:27:38-04:00" level=panic msg="It's over 9000!" animal=orca size=9009
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

To ensure this behaviour even if a TTY is attached, set your formatter as follows:

	log.SetFormatter(&log.TextFormatter{
		DisableColors: true,
		FullTimestamp: true,
	})
Logging Method Name

If you wish to add the calling method as a field, instruct the logger via:

log.SetReportCaller(true)

This adds the caller as 'method' like so:

{"animal":"penguin","level":"fatal","method":"github.com/hrxu01/arcticcreatures.migrate","msg":"a penguin swims by",
"time":"2014-03-10 19:57:38.562543129 -0400 EDT"}

time="2015-03-26T01:27:38-04:00" level=fatal method=github.com/hrxu01/arcticcreatures.migrate msg="a penguin swims by" animal=penguin

Note that this does add measurable overhead - the cost will depend on the version of Go, but is between 20 and 40% in recent tests with 1.6 and 1.7. You can validate this in your environment via benchmarks:

go test -bench=.*CallerTracing
Case-sensitivity

The organization's name was changed to lower-case--and this will not be changed back. If you are getting import conflicts due to case sensitivity, please use the lower-case import: github.com/hrxu01/logrus.

Example

The simplest way to use Logrus is simply the package-level exported logger:

package main

import (
  log "github.com/hrxu01/logrus"
)

func main() {
  log.WithFields(log.Fields{
    "animal": "walrus",
  }).Info("A walrus appears")
}

Note that it's completely api-compatible with the stdlib logger, so you can replace your log imports everywhere with log "github.com/hrxu01/logrus" and you'll now have the flexibility of Logrus. You can customize it all you want:

package main

import (
  "os"
  log "github.com/hrxu01/logrus"
)

func init() {
  // Log as JSON instead of the default ASCII formatter.
  log.SetFormatter(&log.JSONFormatter{})

  // Output to stdout instead of the default stderr
  // Can be any io.Writer, see below for File example
  log.SetOutput(os.Stdout)

  // Only log the warning severity or above.
  log.SetLevel(log.WarnLevel)
}

func main() {
  log.WithFields(log.Fields{
    "animal": "walrus",
    "size":   10,
  }).Info("A group of walrus emerges from the ocean")

  log.WithFields(log.Fields{
    "omg":    true,
    "number": 122,
  }).Warn("The group's number increased tremendously!")

  log.WithFields(log.Fields{
    "omg":    true,
    "number": 100,
  }).Fatal("The ice breaks!")

  // A common pattern is to re-use fields between logging statements by re-using
  // the logrus.Entry returned from WithFields()
  contextLogger := log.WithFields(log.Fields{
    "common": "this is a common field",
    "other": "I also should be logged always",
  })

  contextLogger.Info("I'll be logged with common and other field")
  contextLogger.Info("Me too")
}

For more advanced usage such as logging to multiple locations from the same application, you can also create an instance of the logrus Logger:

package main

import (
  "os"
  "github.com/hrxu01/logrus"
)

// Create a new instance of the logger. You can have any number of instances.
var log = logrus.New()

func main() {
  // The API for setting attributes is a little different than the package level
  // exported logger. See Godoc.
  log.Out = os.Stdout

  // You could set this to any `io.Writer` such as a file
  // file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY, 0666)
  // if err == nil {
  //  log.Out = file
  // } else {
  //  log.Info("Failed to log to file, using default stderr")
  // }

  log.WithFields(logrus.Fields{
    "animal": "walrus",
    "size":   10,
  }).Info("A group of walrus emerges from the ocean")
}
Fields

Logrus encourages careful, structured logging through logging fields instead of long, unparseable error messages. For example, instead of: log.Fatalf("Failed to send event %s to topic %s with key %d"), you should log the much more discoverable:

log.WithFields(log.Fields{
  "event": event,
  "topic": topic,
  "key": key,
}).Fatal("Failed to send event")

We've found this API forces you to think about logging in a way that produces much more useful logging messages. We've been in countless situations where just a single added field to a log statement that was already there would've saved us hours. The WithFields call is optional.

In general, with Logrus using any of the printf-family functions should be seen as a hint you should add a field, however, you can still use the printf-family functions with Logrus.

Default Fields

Often it's helpful to have fields always attached to log statements in an application or parts of one. For example, you may want to always log the request_id and user_ip in the context of a request. Instead of writing log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip}) on every line, you can create a logrus.Entry to pass around instead:

requestLogger := log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip})
requestLogger.Info("something happened on that request") # will log request_id and user_ip
requestLogger.Warn("something not great happened")
Hooks

You can add hooks for logging levels. For example to send errors to an exception tracking service on Error, Fatal and Panic, info to StatsD or log to multiple places simultaneously, e.g. syslog.

Logrus comes with built-in hooks. Add those, or your custom hook, in init:

import (
  log "github.com/hrxu01/logrus"
  "gopkg.in/gemnasium/logrus-airbrake-hook.v2" // the package is named "airbrake"
  logrus_syslog "github.com/hrxu01/logrus/hooks/syslog"
  "log/syslog"
)

func init() {

  // Use the Airbrake hook to report errors that have Error severity or above to
  // an exception tracker. You can create custom hooks, see the Hooks section.
  log.AddHook(airbrake.NewHook(123, "xyz", "production"))

  hook, err := logrus_syslog.NewSyslogHook("udp", "localhost:514", syslog.LOG_INFO, "")
  if err != nil {
    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.

A list of currently known of service hook can be found in this wiki page

Level logging

Logrus has seven logging levels: Trace, Debug, Info, Warning, Error, Fatal and Panic.

log.Trace("Something very low level.")
log.Debug("Useful debugging information.")
log.Info("Something noteworthy happened!")
log.Warn("You should probably take a look at this.")
log.Error("Something failed but I'm not quitting.")
// Calls os.Exit(1) after logging
log.Fatal("Bye.")
// Calls panic() after logging
log.Panic("I'm bailing.")

You can set the logging level on a Logger, then it will only log entries with that severity or anything above it:

// Will log anything that is info or above (warn, error, fatal, panic). Default.
log.SetLevel(log.InfoLevel)

It may be useful to set log.Level = logrus.DebugLevel in a debug or verbose environment if your application has that.

Entries

Besides the fields added with WithField or WithFields some fields are automatically added to all logging events:

  1. time. The timestamp when the entry was created.
  2. msg. The logging message passed to {Info,Warn,Error,Fatal,Panic} after the AddFields call. E.g. Failed to send event.
  3. level. The logging level. E.g. info.
Environments

Logrus has no notion of environment.

If you wish for hooks and formatters to only be used in specific environments, you should handle that yourself. For example, if your application has a global variable Environment, which is a string representation of the environment you could do:

import (
  log "github.com/hrxu01/logrus"
)

init() {
  // do something here to set environment depending on an environment variable
  // or command-line flag
  if Environment == "production" {
    log.SetFormatter(&log.JSONFormatter{})
  } else {
    // The TextFormatter is default, you don't actually have to do this.
    log.SetFormatter(&log.TextFormatter{})
  }
}

This configuration is how logrus was intended to be used, but JSON in production is mostly only useful if you do log aggregation with tools like Splunk or Logstash.

Formatters

The built-in logging formatters are:

  • logrus.TextFormatter. Logs the event in colors if stdout is a tty, otherwise without colors.
    • Note: to force colored output when there is no TTY, set the ForceColors field to true. To force no colored output even if there is a TTY set the DisableColors field to true. For Windows, see github.com/mattn/go-colorable.
    • When colors are enabled, levels are truncated to 4 characters by default. To disable truncation set the DisableLevelTruncation field to true.
    • All options are listed in the generated docs.
  • logrus.JSONFormatter. Logs fields as JSON.

Third party logging formatters:

  • FluentdFormatter. Formats entries that can be parsed by Kubernetes and Google Container Engine.
  • GELF. Formats entries so they comply to Graylog's GELF 1.1 specification.
  • logstash. Logs fields as Logstash Events.
  • prefixed. Displays log entry source along with alternative layout.
  • zalgo. Invoking the P͉̫o̳̼̊w̖͈̰͎e̬͔̭͂r͚̼̹̲ ̫͓͉̳͈ō̠͕͖̚f̝͍̠ ͕̲̞͖͑Z̖̫̤̫ͪa͉̬͈̗l͖͎g̳̥o̰̥̅!̣͔̲̻͊̄ ̙̘̦̹̦.
  • nested-logrus-formatter. Converts logrus fields to a nested structure.

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):

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, %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.

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:

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 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 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. sample
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):
import(
  "github.com/hrxu01/logrus"
  "github.com/hrxu01/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 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 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 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/)

Documentation

Overview

Package logrus is a structured logger for Go, completely API compatible with the standard library logger.

The simplest way to use Logrus is simply the package-level exported logger: 

package main

import (
  log "github.com/hrxu01/logrus"
)

func main() {
  log.WithFields(log.Fields{
    "animal": "walrus",
    "number": 1,
    "size":   10,
  }).Info("A walrus appears")
}

Output: 

time="2015-09-07T08:48:33Z" level=info msg="A walrus appears" animal=walrus number=1 size=10

For a full guide visit https://github.com/hrxu01/logrus

Example (Basic) 
package main

import (
	"os"

	"github.com/hrxu01/logrus"
)

func main() {
	var log = logrus.New()
	log.Formatter = new(logrus.JSONFormatter)
	log.Formatter = new(logrus.TextFormatter)                     //default
	log.Formatter.(*logrus.TextFormatter).DisableColors = true    // remove colors
	log.Formatter.(*logrus.TextFormatter).DisableTimestamp = true // remove timestamp from test output
	log.Level = logrus.TraceLevel
	log.Out = os.Stdout

	// file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY, 0666)
	// if err == nil {
	// 	log.Out = file
	// } else {
	// 	log.Info("Failed to log to file, using default stderr")
	// }

	defer func() {
		err := recover()
		if err != nil {
			entry := err.(*logrus.Entry)
			log.WithFields(logrus.Fields{
				"omg":         true,
				"err_animal":  entry.Data["animal"],
				"err_size":    entry.Data["size"],
				"err_level":   entry.Level,
				"err_message": entry.Message,
				"number":      100,
			}).Error("The ice breaks!") // or use Fatal() to force the process to exit with a nonzero code
		}
	}()

	log.WithFields(logrus.Fields{
		"animal": "walrus",
		"number": 0,
	}).Trace("Went to the beach")

	log.WithFields(logrus.Fields{
		"animal": "walrus",
		"number": 8,
	}).Debug("Started observing beach")

	log.WithFields(logrus.Fields{
		"animal": "walrus",
		"size":   10,
	}).Info("A group of walrus emerges from the ocean")

	log.WithFields(logrus.Fields{
		"omg":    true,
		"number": 122,
	}).Warn("The group's number increased tremendously!")

	log.WithFields(logrus.Fields{
		"temperature": -4,
	}).Debug("Temperature changes")

	log.WithFields(logrus.Fields{
		"animal": "orca",
		"size":   9009,
	}).Panic("It's over 9000!")

}

Output:

level=trace msg="Went to the beach" animal=walrus number=0
level=debug msg="Started observing beach" animal=walrus number=8
level=info msg="A group of walrus emerges from the ocean" animal=walrus size=10
level=warning msg="The group's number increased tremendously!" number=122 omg=true
level=debug msg="Temperature changes" temperature=-4
level=panic msg="It's over 9000!" animal=orca size=9009
level=error msg="The ice breaks!" err_animal=orca err_level=panic err_message="It's over 9000!" err_size=9009 number=100 omg=true
Example (Hook)

An example on how to use a hook 

package main

import (
	"log/syslog"
	"os"

	"github.com/hrxu01/logrus"
	slhooks "github.com/hrxu01/logrus/hooks/syslog"
)

func main() {
	var log = logrus.New()
	log.Formatter = new(logrus.TextFormatter)                     // default
	log.Formatter.(*logrus.TextFormatter).DisableColors = true    // remove colors
	log.Formatter.(*logrus.TextFormatter).DisableTimestamp = true // remove timestamp from test output
	if sl, err := slhooks.NewSyslogHook("udp", "localhost:514", syslog.LOG_INFO, ""); err == nil {
		log.Hooks.Add(sl)
	}
	log.Out = os.Stdout

	log.WithFields(logrus.Fields{
		"animal": "walrus",
		"size":   10,
	}).Info("A group of walrus emerges from the ocean")

	log.WithFields(logrus.Fields{
		"omg":    true,
		"number": 122,
	}).Warn("The group's number increased tremendously!")

	log.WithFields(logrus.Fields{
		"omg":    true,
		"number": 100,
	}).Error("The ice breaks!")

}

Output:

level=info msg="A group of walrus emerges from the ocean" animal=walrus size=10
level=warning msg="The group's number increased tremendously!" number=122 omg=true
level=error msg="The ice breaks!" number=100 omg=true

Index

Examples

Constants

View Source 
const (
	FieldKeyMsg         = "msg"
	FieldKeyLevel       = "level"
	FieldKeyTime        = "time"
	FieldKeyLogrusError = "logrus_error"
	FieldKeyFunc        = "func"
	FieldKeyFile        = "file"
)

Default key names for the default fields

Variables

View Source 
var AllLevels = []Level{
	PanicLevel,
	FatalLevel,
	ErrorLevel,
	WarnLevel,
	InfoLevel,
	DebugLevel,
	TraceLevel,
}

A constant exposing all logging levels

View Source 
var ErrorKey = "error"

Defines the key when adding errors using WithError.

Functions

func AddHook added in v0.4.0 

func AddHook(hook Hook)

AddHook adds a hook to the standard logger hooks.

func Debug 

func Debug(args ...interface{})

Debug logs a message at level Debug on the standard logger.

func Debugf added in v0.4.1 

func Debugf(format string, args ...interface{})

Debugf logs a message at level Debug on the standard logger.

func Debugln added in v0.4.1 

func Debugln(args ...interface{})

Debugln logs a message at level Debug on the standard logger.

func DeferExitHandler added in v1.4.2 

func DeferExitHandler(handler func())

DeferExitHandler prepends a Logrus Exit handler to the list of handlers, call logrus.Exit to invoke all handlers. The handlers will also be invoked when any Fatal log entry is made.

This method is useful when a caller wishes to use logrus to log a fatal message but also needs to gracefully shutdown. An example usecase could be closing database connections, or sending a alert that the application is closing.

func Error 

func Error(args ...interface{})

Error logs a message at level Error on the standard logger.

func Errorf added in v0.4.1 

func Errorf(format string, args ...interface{})

Errorf logs a message at level Error on the standard logger.

func Errorln added in v0.4.1 

func Errorln(args ...interface{})

Errorln logs a message at level Error on the standard logger.

func Exit added in v0.11.0 

func Exit(code int)

Exit runs all the Logrus atexit handlers and then terminates the program using os.Exit(code)

func Fatal 

func Fatal(args ...interface{})

Fatal logs a message at level Fatal on the standard logger then the process will exit with status set to 1.

func Fatalf added in v0.4.1 

func Fatalf(format string, args ...interface{})

Fatalf logs a message at level Fatal on the standard logger then the process will exit with status set to 1.

func Fatalln added in v0.4.1 

func Fatalln(args ...interface{})

Fatalln logs a message at level Fatal on the standard logger then the process will exit with status set to 1.

func Info 

func Info(args ...interface{})

Info logs a message at level Info on the standard logger.

func Infof added in v0.4.1 

func Infof(format string, args ...interface{})

Infof logs a message at level Info on the standard logger.

func Infoln added in v0.4.1 

func Infoln(args ...interface{})

Infoln logs a message at level Info on the standard logger.

func IsLevelEnabled added in v1.4.2 

func IsLevelEnabled(level Level) bool

IsLevelEnabled checks if the log level of the standard logger is greater than the level param

func Panic 

func Panic(args ...interface{})

Panic logs a message at level Panic on the standard logger.

func Panicf added in v0.4.1 

func Panicf(format string, args ...interface{})

Panicf logs a message at level Panic on the standard logger.

func Panicln added in v0.4.1 

func Panicln(args ...interface{})

Panicln logs a message at level Panic on the standard logger.

func Print added in v0.4.1 

func Print(args ...interface{})

Print logs a message at level Info on the standard logger.

func Printf added in v0.4.1 

func Printf(format string, args ...interface{})

Printf logs a message at level Info on the standard logger.

func Println added in v0.4.1 

func Println(args ...interface{})

Println logs a message at level Info on the standard logger.

func RegisterExitHandler added in v0.11.0 

func RegisterExitHandler(handler func())

RegisterExitHandler appends a Logrus Exit handler to the list of handlers, call logrus.Exit to invoke all handlers. The handlers will also be invoked when any Fatal log entry is made.

This method is useful when a caller wishes to use logrus to log a fatal message but also needs to gracefully shutdown. An example usecase could be closing database connections, or sending a alert that the application is closing.

func SetFormatter added in v0.4.0 

func SetFormatter(formatter Formatter)

SetFormatter sets the standard logger formatter.

func SetLevel added in v0.4.0 

func SetLevel(level Level)

SetLevel sets the standard logger level.

func SetOutput added in v0.4.0 

func SetOutput(out io.Writer)

SetOutput sets the standard logger output.

func SetReportCaller added in v1.4.2 

func SetReportCaller(include bool)

SetReportCaller sets whether the standard logger will include the calling method as a field.

func Trace added in v1.4.2 

func Trace(args ...interface{})

Trace logs a message at level Trace on the standard logger.

func Tracef added in v1.4.2 

func Tracef(format string, args ...interface{})

Tracef logs a message at level Trace on the standard logger.

func Traceln added in v1.4.2 

func Traceln(args ...interface{})

Traceln logs a message at level Trace on the standard logger.

func Warn 

func Warn(args ...interface{})

Warn logs a message at level Warn on the standard logger.

func Warnf added in v0.4.1 

func Warnf(format string, args ...interface{})

Warnf logs a message at level Warn on the standard logger.

func Warning added in v0.4.1 

func Warning(args ...interface{})

Warning logs a message at level Warn on the standard logger.

func Warningf added in v0.4.1 

func Warningf(format string, args ...interface{})

Warningf logs a message at level Warn on the standard logger.

func Warningln added in v0.4.1 

func Warningln(args ...interface{})

Warningln logs a message at level Warn on the standard logger.

func Warnln added in v0.4.1 

func Warnln(args ...interface{})

Warnln logs a message at level Warn on the standard logger.

Types

type Entry 

type Entry struct {
	Logger *Logger

	// Contains all the fields set by the user.
	Data Fields

	// Time at which the log entry was created
	Time time.Time

	// Level the log entry was logged at: Trace, Debug, Info, Warn, Error, Fatal or Panic
	// This field will be set on entry firing and the value will be equal to the one in Logger struct field.
	Level Level

	// Calling method, with package name
	Caller *runtime.Frame

	// Message passed to Trace, Debug, Info, Warn, Error, Fatal or Panic
	Message string

	// When formatter is called in entry.log(), a Buffer may be set to entry
	Buffer *bytes.Buffer

	// Contains the context set by the user. Useful for hook processing etc.
	Context context.Context
	// contains filtered or unexported fields
}

An entry is the final or intermediate Logrus logging entry. It contains all the fields passed with WithField{,s}. It's finally logged when Trace, Debug, Info, Warn, Error, Fatal or Panic is called on it. These objects can be reused and passed around as much as you wish to avoid field duplication.

func NewEntry 

func NewEntry(logger *Logger) *Entry

func WithContext added in v1.4.2 

func WithContext(ctx context.Context) *Entry

WithContext creates an entry from the standard logger and adds a context to it.

func WithError added in v0.8.7 

func WithError(err error) *Entry

WithError creates an entry from the standard logger and adds an error to it, using the value defined in ErrorKey as key.

func WithField added in v0.4.0 

func WithField(key string, value interface{}) *Entry

WithField creates an entry from the standard logger and adds a field to it. If you want multiple fields, use `WithFields`.

Note that it doesn't log until you call Debug, Print, Info, Warn, Fatal or Panic on the Entry it returns.

func WithFields added in v0.4.0 

func WithFields(fields Fields) *Entry

WithFields creates an entry from the standard logger and adds multiple fields to it. This is simply a helper for `WithField`, invoking it once for each field.

Note that it doesn't log until you call Debug, Print, Info, Warn, Fatal or Panic on the Entry it returns.

func WithTime added in v1.0.6 

func WithTime(t time.Time) *Entry

WithTime creats an entry from the standard logger and overrides the time of logs generated with it.

Note that it doesn't log until you call Debug, Print, Info, Warn, Fatal or Panic on the Entry it returns.

func (*Entry) Debug 

func (entry *Entry) Debug(args ...interface{})

func (*Entry) Debugf 

func (entry *Entry) Debugf(format string, args ...interface{})

func (*Entry) Debugln 

func (entry *Entry) Debugln(args ...interface{})

func (*Entry) Error 

func (entry *Entry) Error(args ...interface{})

func (*Entry) Errorf 

func (entry *Entry) Errorf(format string, args ...interface{})

func (*Entry) Errorln 

func (entry *Entry) Errorln(args ...interface{})

func (*Entry) Fatal 

func (entry *Entry) Fatal(args ...interface{})

func (*Entry) Fatalf 

func (entry *Entry) Fatalf(format string, args ...interface{})

func (*Entry) Fatalln 

func (entry *Entry) Fatalln(args ...interface{})

func (Entry) HasCaller added in v1.4.2 

func (entry Entry) HasCaller() (has bool)

func (*Entry) Info 

func (entry *Entry) Info(args ...interface{})

func (*Entry) Infof 

func (entry *Entry) Infof(format string, args ...interface{})

func (*Entry) Infoln 

func (entry *Entry) Infoln(args ...interface{})

func (*Entry) Log added in v1.4.2 

func (entry *Entry) Log(level Level, args ...interface{})

func (*Entry) Logf added in v1.4.2 

func (entry *Entry) Logf(level Level, format string, args ...interface{})

func (*Entry) Logln added in v1.4.2 

func (entry *Entry) Logln(level Level, args ...interface{})

func (*Entry) Panic 

func (entry *Entry) Panic(args ...interface{})

func (*Entry) Panicf 

func (entry *Entry) Panicf(format string, args ...interface{})

func (*Entry) Panicln 

func (entry *Entry) Panicln(args ...interface{})

func (*Entry) Print 

func (entry *Entry) Print(args ...interface{})

func (*Entry) Printf 

func (entry *Entry) Printf(format string, args ...interface{})

func (*Entry) Println 

func (entry *Entry) Println(args ...interface{})

func (*Entry) String 

func (entry *Entry) String() (string, error)

Returns the string representation from the reader and ultimately the formatter.

func (*Entry) Trace added in v1.4.2 

func (entry *Entry) Trace(args ...interface{})

func (*Entry) Tracef added in v1.4.2 

func (entry *Entry) Tracef(format string, args ...interface{})

func (*Entry) Traceln added in v1.4.2 

func (entry *Entry) Traceln(args ...interface{})

func (*Entry) Warn 

func (entry *Entry) Warn(args ...interface{})

func (*Entry) Warnf 

func (entry *Entry) Warnf(format string, args ...interface{})

func (*Entry) Warning added in v0.6.3 

func (entry *Entry) Warning(args ...interface{})

func (*Entry) Warningf 

func (entry *Entry) Warningf(format string, args ...interface{})

func (*Entry) Warningln 

func (entry *Entry) Warningln(args ...interface{})

func (*Entry) Warnln 

func (entry *Entry) Warnln(args ...interface{})

func (*Entry) WithContext added in v1.4.2 

func (entry *Entry) WithContext(ctx context.Context) *Entry

Add a context to the Entry.

func (*Entry) WithError added in v0.8.7 

func (entry *Entry) WithError(err error) *Entry

Add an error as single field (using the key defined in ErrorKey) to the Entry.

func (*Entry) WithField 

func (entry *Entry) WithField(key string, value interface{}) *Entry

Add a single field to the Entry.

func (*Entry) WithFields 

func (entry *Entry) WithFields(fields Fields) *Entry

Add a map of fields to the Entry.

func (*Entry) WithTime added in v1.0.6 

func (entry *Entry) WithTime(t time.Time) *Entry

Overrides the time of the Entry.

func (*Entry) Writer added in v0.11.5 

func (entry *Entry) Writer() *io.PipeWriter

func (*Entry) WriterLevel added in v0.11.5 

func (entry *Entry) WriterLevel(level Level) *io.PipeWriter

type Ext1FieldLogger added in v1.4.2 

type Ext1FieldLogger interface {
	FieldLogger
	Tracef(format string, args ...interface{})
	Trace(args ...interface{})
	Traceln(args ...interface{})
}

Ext1FieldLogger (the first extension to FieldLogger) is superfluous, it is here for consistancy. Do not use. Use Logger or Entry instead.

type FieldLogger added in v0.10.0 

type FieldLogger interface {
	WithField(key string, value interface{}) *Entry
	WithFields(fields Fields) *Entry
	WithError(err error) *Entry

	Debugf(format string, args ...interface{})
	Infof(format string, args ...interface{})
	Printf(format string, args ...interface{})
	Warnf(format string, args ...interface{})
	Warningf(format string, args ...interface{})
	Errorf(format string, args ...interface{})
	Fatalf(format string, args ...interface{})
	Panicf(format string, args ...interface{})

	Debug(args ...interface{})
	Info(args ...interface{})
	Print(args ...interface{})
	Warn(args ...interface{})
	Warning(args ...interface{})
	Error(args ...interface{})
	Fatal(args ...interface{})
	Panic(args ...interface{})

	Debugln(args ...interface{})
	Infoln(args ...interface{})
	Println(args ...interface{})
	Warnln(args ...interface{})
	Warningln(args ...interface{})
	Errorln(args ...interface{})
	Fatalln(args ...interface{})
	Panicln(args ...interface{})
}

The FieldLogger interface generalizes the Entry and Logger types

type FieldMap added in v0.11.1 

type FieldMap map[fieldKey]string

FieldMap allows customization of the key names for default fields.

type Fields 

type Fields map[string]interface{}

Fields type, used to pass to `WithFields`.

type Formatter 

type Formatter interface {
	Format(*Entry) ([]byte, error)
}

The Formatter interface is used to implement a custom Formatter. It takes an `Entry`. It exposes all the fields, including the default ones:

* `entry.Data["msg"]`. The message passed from Info, Warn, Error .. * `entry.Data["time"]`. The timestamp. * `entry.Data["level"]. The level the entry was logged at.

Any additional fields added with `WithField` or `WithFields` are also in `entry.Data`. Format is expected to return an array of bytes which are then logged to `logger.Out`.

type Hook 

type Hook interface {
	Levels() []Level
	Fire(*Entry) error
}

A hook to be fired when logging on the logging levels returned from `Levels()` on your implementation of the interface. Note that this is not fired in a goroutine or a channel with workers, you should handle such functionality yourself if your call is non-blocking and you don't wish for the logging calls for levels returned from `Levels()` to block.

type JSONFormatter 

type JSONFormatter struct {
	// TimestampFormat sets the format used for marshaling timestamps.
	TimestampFormat string

	// DisableTimestamp allows disabling automatic timestamps in output
	DisableTimestamp bool

	// DataKey allows users to put all the log entry parameters into a nested dictionary at a given key.
	DataKey string

	// FieldMap allows users to customize the names of keys for default fields.
	// As an example:
	// formatter := &JSONFormatter{
	//   	FieldMap: FieldMap{
	// 		 FieldKeyTime:  "@timestamp",
	// 		 FieldKeyLevel: "@level",
	// 		 FieldKeyMsg:   "@message",
	// 		 FieldKeyFunc:  "@caller",
	//    },
	// }
	FieldMap FieldMap

	// CallerPrettyfier can be set by the user to modify the content
	// of the function and file keys in the json data when ReportCaller is
	// activated. If any of the returned value is the empty string the
	// corresponding key will be removed from json fields.
	CallerPrettyfier func(*runtime.Frame) (function string, file string)

	// PrettyPrint will indent all json logs
	PrettyPrint bool
}

JSONFormatter formats logs into parsable json

func (*JSONFormatter) Format 

func (f *JSONFormatter) Format(entry *Entry) ([]byte, error)

Format renders a single log entry

type Level 

type Level uint32

Level type 

const (
	// PanicLevel level, highest level of severity. Logs and then calls panic with the
	// message passed to Debug, Info, ...
	PanicLevel Level = iota
	// FatalLevel level. Logs and then calls `logger.Exit(1)`. It will exit even if the
	// logging level is set to Panic.
	FatalLevel
	// ErrorLevel level. Logs. Used for errors that should definitely be noted.
	// Commonly used for hooks to send errors to an error tracking service.
	ErrorLevel
	// WarnLevel level. Non-critical entries that deserve eyes.
	WarnLevel
	// InfoLevel level. General operational entries about what's going on inside the
	// application.
	InfoLevel
	// DebugLevel level. Usually only enabled when debugging. Very verbose logging.
	DebugLevel
	// TraceLevel level. Designates finer-grained informational events than the Debug.
	TraceLevel
)

These are the different logging levels. You can set the logging level to log on your instance of logger, obtained with `logrus.New()`.

func GetLevel added in v0.6.1 

func GetLevel() Level

GetLevel returns the standard logger level.

func ParseLevel added in v0.6.0 

func ParseLevel(lvl string) (Level, error)

ParseLevel takes a string level and returns the Logrus log level constant.

func (Level) MarshalText added in v1.4.2 

func (level Level) MarshalText() ([]byte, error)

func (Level) String added in v0.4.0 

func (level Level) String() string

Convert the Level to a string. E.g. PanicLevel becomes "panic".

func (*Level) UnmarshalText added in v1.4.2 

func (level *Level) UnmarshalText(text []byte) error

UnmarshalText implements encoding.TextUnmarshaler.

type LevelHooks added in v0.8.3 

type LevelHooks map[Level][]Hook

Internal type for storing the hooks on a logger instance.

func (LevelHooks) Add added in v0.8.3 

func (hooks LevelHooks) Add(hook Hook)

Add a hook to an instance of logger. This is called with `log.Hooks.Add(new(MyHook))` where `MyHook` implements the `Hook` interface.

func (LevelHooks) Fire added in v0.8.3 

func (hooks LevelHooks) Fire(level Level, entry *Entry) error

Fire all the hooks for the passed level. Used by `entry.log` to fire appropriate hooks for a log entry.

type Logger 

type Logger struct {
	// The logs are `io.Copy`'d to this in a mutex. It's common to set this to a
	// file, or leave it default which is `os.Stderr`. You can also set this to
	// something more adventurous, such as logging to Kafka.
	Out io.Writer
	// Hooks for the logger instance. These allow firing events based on logging
	// levels and log entries. For example, to send errors to an error tracking
	// service, log to StatsD or dump the core on fatal errors.
	Hooks LevelHooks
	// All log entries pass through the formatter before logged to Out. The
	// included formatters are `TextFormatter` and `JSONFormatter` for which
	// TextFormatter is the default. In development (when a TTY is attached) it
	// logs with colors, but to a file it wouldn't. You can easily implement your
	// own that implements the `Formatter` interface, see the `README` or included
	// formatters for examples.
	Formatter Formatter

	// Flag for whether to log caller info (off by default)
	ReportCaller bool

	// The logging level the logger should log at. This is typically (and defaults
	// to) `logrus.Info`, which allows Info(), Warn(), Error() and Fatal() to be
	// logged.
	Level Level

	// Function to exit the application, defaults to `os.Exit()`
	ExitFunc exitFunc
	// contains filtered or unexported fields
}

func New 

func New() *Logger

Creates a new logger. Configuration should be set by changing `Formatter`, `Out` and `Hooks` directly on the default logger instance. You can also just instantiate your own: 

var log = &Logger{
  Out: os.Stderr,
  Formatter: new(JSONFormatter),
  Hooks: make(LevelHooks),
  Level: logrus.DebugLevel,
}

It's recommended to make this a global instance called `log`.

func StandardLogger added in v0.6.5 

func StandardLogger() *Logger

func (*Logger) AddHook added in v1.0.4 

func (logger *Logger) AddHook(hook Hook)

AddHook adds a hook to the logger hooks.

func (*Logger) Debug 

func (logger *Logger) Debug(args ...interface{})

func (*Logger) Debugf 

func (logger *Logger) Debugf(format string, args ...interface{})

func (*Logger) Debugln 

func (logger *Logger) Debugln(args ...interface{})

func (*Logger) Error 

func (logger *Logger) Error(args ...interface{})

func (*Logger) Errorf 

func (logger *Logger) Errorf(format string, args ...interface{})

func (*Logger) Errorln 

func (logger *Logger) Errorln(args ...interface{})

func (*Logger) Exit added in v1.4.2 

func (logger *Logger) Exit(code int)

func (*Logger) Fatal 

func (logger *Logger) Fatal(args ...interface{})

func (*Logger) Fatalf 

func (logger *Logger) Fatalf(format string, args ...interface{})

func (*Logger) Fatalln 

func (logger *Logger) Fatalln(args ...interface{})

func (*Logger) GetLevel added in v1.4.2 

func (logger *Logger) GetLevel() Level

GetLevel returns the logger level.

func (*Logger) Info 

func (logger *Logger) Info(args ...interface{})

func (*Logger) Infof 

func (logger *Logger) Infof(format string, args ...interface{})

func (*Logger) Infoln 

func (logger *Logger) Infoln(args ...interface{})

func (*Logger) IsLevelEnabled added in v1.4.2 

func (logger *Logger) IsLevelEnabled(level Level) bool

IsLevelEnabled checks if the log level of the logger is greater than the level param

func (*Logger) Log added in v1.4.2 

func (logger *Logger) Log(level Level, args ...interface{})

func (*Logger) Logf added in v1.4.2 

func (logger *Logger) Logf(level Level, format string, args ...interface{})

func (*Logger) Logln added in v1.4.2 

func (logger *Logger) Logln(level Level, args ...interface{})

func (*Logger) Panic 

func (logger *Logger) Panic(args ...interface{})

func (*Logger) Panicf 

func (logger *Logger) Panicf(format string, args ...interface{})

func (*Logger) Panicln 

func (logger *Logger) Panicln(args ...interface{})

func (*Logger) Print 

func (logger *Logger) Print(args ...interface{})

func (*Logger) Printf 

func (logger *Logger) Printf(format string, args ...interface{})

func (*Logger) Println 

func (logger *Logger) Println(args ...interface{})

func (*Logger) ReplaceHooks added in v1.4.2 

func (logger *Logger) ReplaceHooks(hooks LevelHooks) LevelHooks

ReplaceHooks replaces the logger hooks and returns the old ones

func (*Logger) SetFormatter added in v1.4.2 

func (logger *Logger) SetFormatter(formatter Formatter)

SetFormatter sets the logger formatter.

func (*Logger) SetLevel added in v1.0.3 

func (logger *Logger) SetLevel(level Level)

SetLevel sets the logger level.

func (*Logger) SetNoLock added in v0.11.0 

func (logger *Logger) SetNoLock()

When file is opened with appending mode, it's safe to write concurrently to a file (within 4k message on Linux). In these cases user can choose to disable the lock.

func (*Logger) SetOutput added in v1.0.6 

func (logger *Logger) SetOutput(output io.Writer)

SetOutput sets the logger output.

func (*Logger) SetReportCaller added in v1.4.2 

func (logger *Logger) SetReportCaller(reportCaller bool)

func (*Logger) Trace added in v1.4.2 

func (logger *Logger) Trace(args ...interface{})

func (*Logger) Tracef added in v1.4.2 

func (logger *Logger) Tracef(format string, args ...interface{})

func (*Logger) Traceln added in v1.4.2 

func (logger *Logger) Traceln(args ...interface{})

func (*Logger) Warn 

func (logger *Logger) Warn(args ...interface{})

func (*Logger) Warnf 

func (logger *Logger) Warnf(format string, args ...interface{})

func (*Logger) Warning 

func (logger *Logger) Warning(args ...interface{})

func (*Logger) Warningf 

func (logger *Logger) Warningf(format string, args ...interface{})

func (*Logger) Warningln 

func (logger *Logger) Warningln(args ...interface{})

func (*Logger) Warnln 

func (logger *Logger) Warnln(args ...interface{})

func (*Logger) WithContext added in v1.4.2 

func (logger *Logger) WithContext(ctx context.Context) *Entry

Add a context to the log entry.

func (*Logger) WithError added in v0.9.0 

func (logger *Logger) WithError(err error) *Entry

Add an error as single field to the log entry. All it does is call `WithError` for the given `error`.

func (*Logger) WithField 

func (logger *Logger) WithField(key string, value interface{}) *Entry

Adds a field to the log entry, note that it doesn't log until you call Debug, Print, Info, Warn, Error, Fatal or Panic. It only creates a log entry. If you want multiple fields, use `WithFields`.

func (*Logger) WithFields 

func (logger *Logger) WithFields(fields Fields) *Entry

Adds a struct of fields to the log entry. All it does is call `WithField` for each `Field`.

func (*Logger) WithTime added in v1.0.6 

func (logger *Logger) WithTime(t time.Time) *Entry

Overrides the time of the log entry.

func (*Logger) Writer added in v0.6.5 

func (logger *Logger) Writer() *io.PipeWriter

func (*Logger) WriterLevel added in v0.11.0 

func (logger *Logger) WriterLevel(level Level) *io.PipeWriter

type MutexWrap added in v0.11.0 

type MutexWrap struct {
	// contains filtered or unexported fields
}

func (*MutexWrap) Disable added in v0.11.0 

func (mw *MutexWrap) Disable()

func (*MutexWrap) Lock added in v0.11.0 

func (mw *MutexWrap) Lock()

func (*MutexWrap) Unlock added in v0.11.0 

func (mw *MutexWrap) Unlock()

type StdLogger 

type StdLogger interface {
	Print(...interface{})
	Printf(string, ...interface{})
	Println(...interface{})

	Fatal(...interface{})
	Fatalf(string, ...interface{})
	Fatalln(...interface{})

	Panic(...interface{})
	Panicf(string, ...interface{})
	Panicln(...interface{})
}

StdLogger is what your logrus-enabled library should take, that way it'll accept a stdlib logger and a logrus logger. There's no standard interface, this is the closest we get, unfortunately.

type TextFormatter 

type TextFormatter struct {
	// Set to true to bypass checking for a TTY before outputting colors.
	ForceColors bool

	// Force disabling colors.
	DisableColors bool

	// Override coloring based on CLICOLOR and CLICOLOR_FORCE. - https://bixense.com/clicolors/
	EnvironmentOverrideColors bool

	// Disable timestamp logging. useful when output is redirected to logging
	// system that already adds timestamps.
	DisableTimestamp bool

	// Enable logging the full timestamp when a TTY is attached instead of just
	// the time passed since beginning of execution.
	FullTimestamp bool

	// TimestampFormat to use for display when a full timestamp is printed
	TimestampFormat string

	// The fields are sorted by default for a consistent output. For applications
	// that log extremely frequently and don't use the JSON formatter this may not
	// be desired.
	DisableSorting bool

	// The keys sorting function, when uninitialized it uses sort.Strings.
	SortingFunc func([]string)

	// Disables the truncation of the level text to 4 characters.
	DisableLevelTruncation bool

	// QuoteEmptyFields will wrap empty fields in quotes if true
	QuoteEmptyFields bool

	// FieldMap allows users to customize the names of keys for default fields.
	// As an example:
	// formatter := &TextFormatter{
	//     FieldMap: FieldMap{
	//         FieldKeyTime:  "@timestamp",
	//         FieldKeyLevel: "@level",
	//         FieldKeyMsg:   "@message"}}
	FieldMap FieldMap

	// CallerPrettyfier can be set by the user to modify the content
	// of the function and file keys in the data when ReportCaller is
	// activated. If any of the returned value is the empty string the
	// corresponding key will be removed from fields.
	CallerPrettyfier func(*runtime.Frame) (function string, file string)
	// contains filtered or unexported fields
}

TextFormatter formats logs into text

func (*TextFormatter) Format 

func (f *TextFormatter) Format(entry *Entry) ([]byte, error)

Format renders a single log entry

Source Files

View all Source files

Directories

Path Synopsis
hooks
syslog
test
The Test package is used for testing logrus.
 The Test package is used for testing logrus.
internal
testutils

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