README ¶
Logrus
Logrus is a structured logger for Go (golang), completely API compatible with
the standard library logger. Godoc. Please note the Logrus API is not
yet stable (pre 1.0), the core API is unlikely change much but please version
control your Logrus to make sure you aren't fetching latest master
on every
build.
Nicely color-coded in development (when a TTY is attached, otherwise just plain text):
With log.Formatter = new(logrus.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.Formatter = new(logrus.TextFormatter)
when a TTY is not
attached, the output is compatible with the
l2met format:
time="2014-04-20 15:36:23.830442383 -0400 EDT" level="info" msg="A group of walrus emerges from the ocean" animal="walrus" size=10
time="2014-04-20 15:36:23.830584199 -0400 EDT" level="warning" msg="The group's number increased tremendously!" omg=true number=122
time="2014-04-20 15:36:23.830596521 -0400 EDT" level="info" msg="A giant walrus appears!" animal="walrus" size=10
time="2014-04-20 15:36:23.830611837 -0400 EDT" level="info" msg="Tremendously sized cow enters the ocean." animal="walrus" size=9
time="2014-04-20 15:36:23.830626464 -0400 EDT" level="fatal" msg="The ice breaks!" omg=true number=100
Example
The simplest way to use Logrus is simply the package-level exported logger:
package main
import (
log "github.com/Sirupsen/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/Sirupsen/logrus"
and you'll now have the flexibility of Logrus. You can customize it all you
want:
package main
import (
"os"
log "github.com/Sirupsen/logrus"
"github.com/Sirupsen/logrus/hooks/airbrake"
)
func init() {
// Log as JSON instead of the default ASCII formatter.
log.SetFormatter(&log.JSONFormatter{})
// 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(&logrus_airbrake.AirbrakeHook{})
// Output to stderr instead of stdout, could also be a file.
log.SetOutput(os.Stderr)
// 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!")
}
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 (
"github.com/Sirupsen/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.Stderr
log.WithFields(logrus.Fields{
"animal": "walrus",
"size": 10,
}).Info("A group of walrus emerges from the ocean")
}
Fields
Logrus encourages careful, structured logging though 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.
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.
// Not the real implementation of the Airbrake hook. Just a simple sample.
import (
log "github.com/Sirupsen/logrus"
)
func init() {
log.AddHook(new(AirbrakeHook))
}
type AirbrakeHook struct{}
// `Fire()` takes the entry that the hook is fired for. `entry.Data[]` contains
// the fields for the entry. See the Fields section of the README.
func (hook *AirbrakeHook) Fire(entry *logrus.Entry) error {
err := airbrake.Notify(entry.Data["error"].(error))
if err != nil {
log.WithFields(log.Fields{
"source": "airbrake",
"endpoint": airbrake.Endpoint,
}).Info("Failed to send error to Airbrake")
}
return nil
}
// `Levels()` returns a slice of `Levels` the hook is fired for.
func (hook *AirbrakeHook) Levels() []log.Level {
return []log.Level{
log.ErrorLevel,
log.FatalLevel,
log.PanicLevel,
}
}
Logrus comes with built-in hooks. Add those, or your custom hook, in init
:
import (
log "github.com/Sirupsen/logrus"
"github.com/Sirupsen/logrus/hooks/airbrake"
"github.com/Sirupsen/logrus/hooks/syslog"
"log/syslog"
)
func init() {
log.AddHook(new(logrus_airbrake.AirbrakeHook))
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)
}
}
-
github.com/Sirupsen/logrus/hooks/airbrake
Send errors to an exception tracking service compatible with the Airbrake API. Usesairbrake-go
behind the scenes. -
github.com/Sirupsen/logrus/hooks/papertrail
Send errors to the Papertrail hosted logging service via UDP. -
github.com/Sirupsen/logrus/hooks/syslog
Send errors to remote syslog server. Uses standard librarylog/syslog
behind the scenes. -
github.com/nubo/hiprus
Send errors to a channel in hipchat. -
github.com/sebest/logrusly
Send logs to Loggly (https://www.loggly.com/)
Level logging
Logrus has six logging levels: Debug, Info, Warning, Error, Fatal and Panic.
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:
time
. The timestamp when the entry was created.msg
. The logging message passed to{Info,Warn,Error,Fatal,Panic}
after theAddFields
call. E.g.Failed to send event.
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/Sirupsen/logrus"
)
init() {
// do something here to set environment depending on an environment variable
// or command-line flag
if Environment == "production" {
log.SetFormatter(logrus.JSONFormatter)
} else {
// The TextFormatter is default, you don't actually have to do this.
log.SetFormatter(logrus.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 totrue
. To force no colored output even if there is a TTY set theDisableColors
field totrue
- Note: to force colored output when there is no TTY, set the
logrus.JSONFormatter
. Logs fields as JSON.
Third party logging formatters:
zalgo
: invoking the P͉̫o̳̼̊w̖͈̰͎e̬͔̭͂r͚̼̹̲ ̫͓͉̳͈ō̠͕͖̚f̝͍̠ ͕̲̞͖͑Z̖̫̤̫ͪa͉̬͈̗l͖͎g̳̥o̰̥̅!̣͔̲̻͊̄ ̙̘̦̹̦.
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 *JSONFormatter) 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
}
Rotation
Log rotation is not provided with Logrus. Log rotation should be done by an
external program (like logrotated(8)
) that can compress and delete old log
entries. It should not be a feature of the application-level logger.
Documentation ¶
Index ¶
- func AddHook(hook Hook)
- func Debug(args ...interface{})
- func Debugf(format string, args ...interface{})
- func Debugln(args ...interface{})
- func Error(args ...interface{})
- func Errorf(format string, args ...interface{})
- func Errorln(args ...interface{})
- func Fatal(args ...interface{})
- func Fatalf(format string, args ...interface{})
- func Fatalln(args ...interface{})
- func Info(args ...interface{})
- func Infof(format string, args ...interface{})
- func Infoln(args ...interface{})
- func IsTerminal() bool
- func Panic(args ...interface{})
- func Panicf(format string, args ...interface{})
- func Panicln(args ...interface{})
- func Print(args ...interface{})
- func Printf(format string, args ...interface{})
- func Println(args ...interface{})
- func SetFormatter(formatter Formatter)
- func SetLevel(level Level)
- func SetOutput(out io.Writer)
- func Warn(args ...interface{})
- func Warnf(format string, args ...interface{})
- func Warning(args ...interface{})
- func Warningf(format string, args ...interface{})
- func Warningln(args ...interface{})
- func Warnln(args ...interface{})
- type Entry
- func (entry *Entry) Debug(args ...interface{})
- func (entry *Entry) Debugf(format string, args ...interface{})
- func (entry *Entry) Debugln(args ...interface{})
- func (entry *Entry) Error(args ...interface{})
- func (entry *Entry) Errorf(format string, args ...interface{})
- func (entry *Entry) Errorln(args ...interface{})
- func (entry *Entry) Fatal(args ...interface{})
- func (entry *Entry) Fatalf(format string, args ...interface{})
- func (entry *Entry) Fatalln(args ...interface{})
- func (entry *Entry) Info(args ...interface{})
- func (entry *Entry) Infof(format string, args ...interface{})
- func (entry *Entry) Infoln(args ...interface{})
- func (entry *Entry) Panic(args ...interface{})
- func (entry *Entry) Panicf(format string, args ...interface{})
- func (entry *Entry) Panicln(args ...interface{})
- func (entry *Entry) Print(args ...interface{})
- func (entry *Entry) Printf(format string, args ...interface{})
- func (entry *Entry) Println(args ...interface{})
- func (entry *Entry) Reader() (*bytes.Buffer, error)
- func (entry *Entry) String() (string, error)
- func (entry *Entry) Warn(args ...interface{})
- func (entry *Entry) Warnf(format string, args ...interface{})
- func (entry *Entry) Warningf(format string, args ...interface{})
- func (entry *Entry) Warningln(args ...interface{})
- func (entry *Entry) Warnln(args ...interface{})
- func (entry *Entry) WithField(key string, value interface{}) *Entry
- func (entry *Entry) WithFields(fields Fields) *Entry
- type Fields
- type Formatter
- type Hook
- type JSONFormatter
- type Level
- type Logger
- func (logger *Logger) Debug(args ...interface{})
- func (logger *Logger) Debugf(format string, args ...interface{})
- func (logger *Logger) Debugln(args ...interface{})
- func (logger *Logger) Error(args ...interface{})
- func (logger *Logger) Errorf(format string, args ...interface{})
- func (logger *Logger) Errorln(args ...interface{})
- func (logger *Logger) Fatal(args ...interface{})
- func (logger *Logger) Fatalf(format string, args ...interface{})
- func (logger *Logger) Fatalln(args ...interface{})
- func (logger *Logger) Info(args ...interface{})
- func (logger *Logger) Infof(format string, args ...interface{})
- func (logger *Logger) Infoln(args ...interface{})
- func (logger *Logger) Panic(args ...interface{})
- func (logger *Logger) Panicf(format string, args ...interface{})
- func (logger *Logger) Panicln(args ...interface{})
- func (logger *Logger) Print(args ...interface{})
- func (logger *Logger) Printf(format string, args ...interface{})
- func (logger *Logger) Println(args ...interface{})
- func (logger *Logger) Warn(args ...interface{})
- func (logger *Logger) Warnf(format string, args ...interface{})
- func (logger *Logger) Warning(args ...interface{})
- func (logger *Logger) Warningf(format string, args ...interface{})
- func (logger *Logger) Warningln(args ...interface{})
- func (logger *Logger) Warnln(args ...interface{})
- func (logger *Logger) WithField(key string, value interface{}) *Entry
- func (logger *Logger) WithFields(fields Fields) *Entry
- type StdLogger
- type Termios
- type TextFormatter
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Debug ¶
func Debug(args ...interface{})
Debug logs a message at level Debug on the standard logger.
func Debugf ¶
func Debugf(format string, args ...interface{})
Debugf logs a message at level Debug on the standard logger.
func Debugln ¶
func Debugln(args ...interface{})
Debugln logs a message at level Debug on the standard logger.
func Error ¶
func Error(args ...interface{})
Error logs a message at level Error on the standard logger.
func Errorf ¶
func Errorf(format string, args ...interface{})
Errorf logs a message at level Error on the standard logger.
func Errorln ¶
func Errorln(args ...interface{})
Errorln logs a message at level Error on the standard logger.
func Fatal ¶
func Fatal(args ...interface{})
Fatal logs a message at level Fatal on the standard logger.
func Fatalf ¶
func Fatalf(format string, args ...interface{})
Fatalf logs a message at level Fatal on the standard logger.
func Fatalln ¶
func Fatalln(args ...interface{})
Fatalln logs a message at level Fatal on the standard logger.
func Info ¶
func Info(args ...interface{})
Info logs a message at level Info on the standard logger.
func Infof ¶
func Infof(format string, args ...interface{})
Infof logs a message at level Info on the standard logger.
func Infoln ¶
func Infoln(args ...interface{})
Infoln logs a message at level Info on the standard logger.
func IsTerminal ¶
func IsTerminal() bool
IsTerminal returns true if the given file descriptor is a terminal.
func Panic ¶
func Panic(args ...interface{})
Panic logs a message at level Panic on the standard logger.
func Panicf ¶
func Panicf(format string, args ...interface{})
Panicf logs a message at level Panic on the standard logger.
func Panicln ¶
func Panicln(args ...interface{})
Panicln logs a message at level Panic on the standard logger.
func Print ¶
func Print(args ...interface{})
Print logs a message at level Info on the standard logger.
func Printf ¶
func Printf(format string, args ...interface{})
Printf logs a message at level Info on the standard logger.
func Println ¶
func Println(args ...interface{})
Println logs a message at level Info on the standard logger.
func SetFormatter ¶
func SetFormatter(formatter Formatter)
SetFormatter sets the standard logger formatter.
func Warn ¶
func Warn(args ...interface{})
Warn logs a message at level Warn on the standard logger.
func Warnf ¶
func Warnf(format string, args ...interface{})
Warnf logs a message at level Warn on the standard logger.
func Warning ¶
func Warning(args ...interface{})
Warning logs a message at level Warn on the standard logger.
func Warningf ¶
func Warningf(format string, args ...interface{})
Warningf 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: Debug, Info, Warn, Error, Fatal or Panic Level Level // Message passed to Debug, Info, Warn, Error, Fatal or Panic Message string }
An entry is the final or intermediate Logrus logging entry. It contains all the fields passed with WithField{,s}. It's finally logged when 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 WithField ¶
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 ¶
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 (*Entry) String ¶
Returns the string representation from the reader and ultimately the formatter.
func (*Entry) WithFields ¶
Add a map of fields to the Entry.
type Formatter ¶
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 ¶
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{}
type Level ¶
type Level uint8
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 `os.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 )
These are the different logging levels. You can set the logging level to log on your instance of logger, obtained with `logrus.New()`.
func ParseLevel ¶
ParseLevel takes a string level and returns the Logrus log level constant.
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.Stdout`. You can also set this to // something more adventorous, 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 // 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. `logrus.Debug` is useful in Level Level // 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 (*Logger) WithField ¶
Adds a field to the log entry, note that you it doesn't log until you call Debug, Print, Info, Warn, Fatal or Panic. It only creates a log entry. Ff you want multiple fields, use `WithFields`.
func (*Logger) WithFields ¶
Adds a struct of fields to the log entry. All it does is call `WithField` for each `Field`.
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.