log

package module
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 Go to latest Published: Aug 11, 2018 License: MIT Imports: 16 Imported by: 0

README

log

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bdlm/log is a fork of the excellent sirupsen/logrus package. This package adds:

  • support for sanitizing strings from log output to aid in preventing leaking sensitive data.
  • additional default fields host and caller.
  • support for suppressing any default field.
  • TTY formatting and coloring of JSON output.
  • updated text formatting for TTY output.
  • updated TTY color scheme.

bdlm/log is a structured logger for Go and is API compatible with the standard libaray log package.

Formats

By default, bdlm/log uses a basic text format:

time="2018-08-10T20:44:08.707-06:00" level="debug" msg="Oh, look, a bird..." data.animal="bird" data.count="1" caller="main.go:32 main.main" host="myhost"
time="2018-08-10T20:44:08.707-06:00" level="info" msg="A group of walrus emerges from the ocean" data.animal="walrus" data.count="20" caller="main.go:36 main.main" host="myhost"
time="2018-08-10T20:44:08.708-06:00" level="warn" msg="The group's number increased tremendously!" data.animal="walrus" data.count="100" caller="main.go:40 main.main" host="myhost"
time="2018-08-10T20:44:08.708-06:00" level="error" msg="Tremendously sized cow enters the ocean." data.animal="cow" data.count="wait, what?" caller="main.go:44 main.main" host="myhost"
time="2018-08-10T20:44:08.708-06:00" level="panic" msg="The walrus are attacking!" data.animal="walrus" data.run="true" caller="main.go:48 main.main" host="myhost"
time="2018-08-10T20:44:08.708-06:00" level="fatal" msg="That could have gone better..." data.dead="true" data.winner="walrus" caller="main.go:24 main.main.func1" host="myhost"

For development, color-coded output formated for humans is automatically enabled when a tty terminal is detected (this can be disabled with log.SetFormatter(&log.TextFormatter{DisableTTY: true})):

JSON formatting is also available with log.SetFormatter(&log.JSONFormatter{}) for easy parsing by logstash or similar:

{"caller":"main.go:32 main.main","data":{"animal":"bird","count":1},"host":"myhost","level":"debug","msg":"Oh, look, a bird...","time":"2018-08-10T20:44:46.177-06:00"}
{"caller":"main.go:36 main.main","data":{"animal":"walrus","count":20},"host":"myhost","level":"info","msg":"A group of walrus emerges from the ocean","time":"2018-08-10T20:44:46.177-06:00"}
{"caller":"main.go:40 main.main","data":{"animal":"walrus","count":100},"host":"myhost","level":"warn","msg":"The group's number increased tremendously!","time":"2018-08-10T20:44:46.177-06:00"}
{"caller":"main.go:44 main.main","data":{"animal":"cow","count":"wait, what?"},"host":"myhost","level":"error","msg":"Tremendously sized cow enters the ocean.","time":"2018-08-10T20:44:46.177-06:00"}
{"caller":"main.go:48 main.main","data":{"animal":"walrus","run":true},"host":"myhost","level":"panic","msg":"The walrus are attacking!","time":"2018-08-10T20:44:46.177-06:00"}
{"caller":"main.go:24 main.main.func1","data":{"dead":true,"winner":"walrus"},"host":"myhost","level":"fatal","msg":"That could have gone better...","time":"2018-08-10T20:44:46.177-06:00"}

The JSON formatter also makes adjustments by default when a tty terminal is detected and can be disabled similarly with log.SetFormatter(&log.JSONFormatter{DisableTTY: true}):

The full list of Formatter properties that can be set is:

// Set to true to bypass checking for a TTY before outputting colors.
ForceTTY bool

// Disable caller data.
DisableCaller bool

// Force disabling colors.
DisableTTY bool

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

// Disable hostname logging.
DisableHostname bool

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

// FieldMap allows users to customize the names of keys for default fields.
// For example:
//  formatter := &TextFormatter{FieldMap: FieldMap{
//    LabelCaller: "@caller",
//    LabelData:   "@data",
//    LabelHost:   "@hostname",
//    LabelLevel:  "@loglevel",
//    LabelMsg:    "@message",
//    LabelTime:   "@timestamp",
//  }}
FieldMap FieldMap

Examples

Simple usage

The simplest way to use bdlm/log is simply the exported package logger:

package main

import (
    log "github.com/bdlm/log"
)

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

Note that it is fully api-compatible with the stdlib logger, so you can replace your log imports everywhere or using a strangler pattern with "github.com/bdlm/log" and add the full logging flexibility to your service without impacting existing code.

Customization

The logger has several options youc an use to further customize it's output in your code:

package main

import (
    "os"
    log "github.com/bdlm/log"
)

func init() {
    // Blacklist a string from appearing in the log. The characters in any
    // substring match to a word that has been added will be replaced with
    // asterisks (*).
    log.AddSecret("some-secret-text")

    // Register a function that will execute prior to the os.Exit call when a
    // fatal error is logged.
    log.RegisterExitHandler(func() {
        // gracefully shutdown something...
    })

    // Log as JSON instead of the default ASCII formatter.
    log.SetFormatter(&log.TextFormatter{
        // Set various formatter options:
        //   DisableCaller:    true
        //   DisableTTY:       true
        //   DisableTimestamp: true
        //   DisableHostname:  true
        //   ForceTTY:         true
        //   TimestampFormat:  "2006"
        //   FieldMap:         FieldMap{LabelMsg: "message"}
    })

    // Output to stdout instead of the default stderr. Can be any io.Writer, see
    // below for a 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 log.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")
}
Secrets

bdlm/log supports a "blacklist" of values that should not be logged. This can be used to help prevent or mitigate leaking secrets into log files:

import (
    "github.com/bdlm/log"
)

func main() {
    log.AddSecret("some-secret-text")
    log.Info("the secret is 'some-secret-text'")

    // Output: the secret is '****************'
}
Advanced usage

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

package main

import (
    "os"
    "github.com/bdlm/log"
)

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

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

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

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

Fields

bdlm/log 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 bdlm/log 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 bdlm/log.

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 log.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.

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

import (
    log "github.com/bdlm/log"
    log_syslog "github.com/bdlm/log/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 := log_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

bdlm/log 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 = log.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.
  4. caller. The filename and line number where the event occurred.
  5. host. The value of the HOSTNAME environment variable, if any.

Environments

bdlm/log 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/bdlm/log"
)

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 bdlm/log 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:

  • log.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 ForceTTY field to true. To force no colored output even if there is a TTY set the DisableTTY field to true. For Windows, see github.com/mattn/go-colorable.
    • All options are listed in the generated docs.
  • log.JSONFormatter. Logs fields as JSON.
Custom log formatting:

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

bdlm/log 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
    // log.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 := log.New()
logger.Formatter = &log.JSONFormatter{}

// Use `bdlm/log` for standard log output
// Note that `log` here references stdlib's log
log.SetOutput(logger.Writer())

Rotation

Log rotation is not provided with bdlm/log. Log rotation should be done by an external program (like logrotate(8)) that can compress and delete old log entries.

Testing

bdlm/log 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/bdlm/log"
    "github.com/bdlm/log/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, log.ErrorLevel, hook.LastEntry().Level)
    assert.Equal(t, "Helloerror", hook.LastEntry().Message)

    hook.Reset()
    assert.Nil(t, hook.LastEntry())
}

Fatal handlers

bdlm/log can register one or more functions that will be called when any fatal level message is logged. The registered handlers will be executed before bdlm/log 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...
}
log.RegisterExitHandler(handler)
// ...
log.Fatal("handler will fire before os.Exit(1) is called")

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 log is a fork of the excellent [`sirupsen/logrus`](https://github.com/bdlm/log) package.

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

Package-level exported logger 

package main

import (
  "github.com/bdlm/log"
)

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

API Compatibility

Note that it is completely api-compatible with the stdlib logger, so you can replace your `log` imports everywhere with `"github.com/bdlm/log"` and you'll have the full flexibility of `bdlm/log` available. You can customize it further in your code: 

package main

import (
  "os"
  log "github.com/bdlm/log"
)

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 a 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")
}

Managing secrets

`bdlm/log` also supports a "blacklist" of values that should not be logged. This can be used to help prevent or mitigate leaking secrets into log files: 

import (
    "github.com/bdlm/log"
)

func main() {
    log.AddSecret("some-secret-text")
    log.Info("the secret is 'some-secret-text'")

    // Output: the secret is '****************'
}

Output to multiple locations

For more advanced usage such as logging to multiple locations from the same application, you can create an instance of the `bdlm/log` Logger: 

package main

import (
  "os"
  "github.com/bdlm/log"
)

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

func main() {
  // The API for setting attributes is a little different than the package level
  // exported logger. See Godoc.
  logger.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 {
  //    logger.Out = file
  //  } else {
  //    logger.Info("Failed to log to file, using default stderr")
  // }

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

Output features

Color-coded output is available when attached to a TTY for development. A JSON formatter is also available for easy parsing by logstash or Splunk: 

log.SetFormatter(&log.JSONFormatter{})

Output: 

{"caller":"main.go:37 main.main","data":{"animal":"walrus"},"host":"myhost","level":"info","msg":"A group of walrus emerges from the ocean","time":"2018-08-10T23:08:02.860Z"}
{"caller":"main.go:61 main.main","host":"myhost","level":"warning","msg":"The group's number increased tremendously!","number":122,"omg":true,"time":"2018-08-10T23:08:02.863Z"}
{"caller":"main.go:99 main.main","data":{"animal":"walrus"},"host":"myhost","level":"info","msg":"A giant walrus appears!","time":"2018-08-10T23:08:02.877Z"}
{"caller":"main.go:61 main.main","data":{"animal":"walrus","host":"myhost","level":"info","msg":"Tremendously sized cow enters the ocean.","time":"2018-08-10T23:08:02.877Z"}
{"caller":"main.go:99 main.main","host":"myhost","level":"fatal","msg":"The ice breaks!","number":100,"omg":true,"time":"2018-08-10T23:08:03.566Z"}

For a full guide visit https://github.com/bdlm/log

Example (Basic) 
package main

import (
	"os"

	"github.com/bdlm/log"
)

func main() {
	var logger = log.New()
	logger.Formatter = new(log.TextFormatter)                     //default
	logger.Formatter.(*log.TextFormatter).DisableTimestamp = true // remove timestamp from test output
	logger.Formatter.(*log.TextFormatter).DisableHostname = true  // remove timestamp from test output
	logger.Formatter.(*log.TextFormatter).DisableCaller = true    // remove caller from test output
	logger.Level = log.DebugLevel
	logger.Out = os.Stdout

	// Capture the panic result
	defer func() {
		err := recover()
		if err != nil {
			entry := err.(*log.Entry)
			logger.WithFields(log.Fields{
				"winner": entry.Data["animal"],
				"dead":   true,
			}).Error("That could have gone better...")
		}
	}()

	logger.WithFields(log.Fields{
		"animal": "bird",
		"count":  1,
	}).Debug("Oh, look, a bird...")
	logger.WithFields(log.Fields{
		"animal": "walrus",
		"count":  20,
	}).Info("A group of walrus emerges from the ocean")
	logger.WithFields(log.Fields{
		"animal": "walrus",
		"count":  100,
	}).Warn("The group's number increased tremendously!")
	logger.WithFields(log.Fields{
		"animal": "cow",
		"run":    "wait, what?",
	}).Error("Tremendously sized cow enters the ocean.")
	logger.WithFields(log.Fields{
		"animal": "walrus",
		"run":    true,
	}).Panic("The walrus are attacking!")

}

Output:

level="debug" msg="Oh, look, a bird..." data.animal="bird" data.count="1"
level="info" msg="A group of walrus emerges from the ocean" data.animal="walrus" data.count="20"
level="warn" msg="The group's number increased tremendously!" data.animal="walrus" data.count="100"
level="error" msg="Tremendously sized cow enters the ocean." data.animal="cow" data.run="wait, what?"
level="panic" msg="The walrus are attacking!" data.animal="walrus" data.run="true"
level="error" msg="That could have gone better..." data.dead="true" data.winner="walrus"

Index

Examples

Constants

View Source 
const (
	LabelCaller = "caller"
	LabelData   = "data"
	LabelHost   = "host"
	LabelLevel  = "level"
	LabelMsg    = "msg"
	LabelTime   = "time"
)

Default key names for the default fields

View Source 
const (
	// DEFAULTColor is the default TTY 'level' color.
	DEFAULTColor = "\033[38;5;46m"
	// ERRColor is the TTY 'level' color for error messages.
	ERRColor = "\033[38;5;208m"
	// FATALColor is the TTY 'level' color for fatal messages.
	FATALColor = "\033[38;5;124m"
	// PANICColor is the TTY 'level' color for panic messages.
	PANICColor = "\033[38;5;196m"
	// WARNColor is the TTY 'level' color for warning messages.
	WARNColor = "\033[38;5;226m"
	// DEBUGColor is the TTY 'level' color for debug messages.
	DEBUGColor = "\033[38;5;245m"
)
View Source 
const RFC3339Milli = "2006-01-02T15:04:05.000Z07:00"

RFC3339Milli defines an RFC3339 date format with miliseconds

Variables

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

AllLevels is a constant exposing all logging levels.

View Source 
var ErrorKey = "error"

ErrorKey defines the key when adding errors using WithError.

Functions

func AddHook 

func AddHook(hook Hook)

AddHook adds a hook to the standard logger hooks.

func AddSecret 

func AddSecret(secret string)

AddSecret adds a string to the sanitization list.

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 Exit 

func Exit(code int)

Exit runs all the exit 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 

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 

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 

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 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 RegisterExitHandler 

func RegisterExitHandler(handler func())

RegisterExitHandler adds an Exit handler, call log.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 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 

func SetFormatter(formatter Formatter)

SetFormatter sets the standard logger formatter.

func SetLevel 

func SetLevel(level Level)

SetLevel sets the standard logger level.

func SetOutput 

func SetOutput(out io.Writer)

SetOutput sets the standard logger output.

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.

func Warningln 

func Warningln(args ...interface{})

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

func Warnln 

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: 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

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

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

Entry is the final or intermediate 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 NewEntry 

func NewEntry(logger *Logger) *Entry

NewEntry returns a new logger entry.

func WithError 

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 

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 

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 

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{})

Debug logs a debug-level message using Println.

func (*Entry) Debugf 

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

Debugf logs a debug-level message using Printf.

func (*Entry) Debugln 

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

Debugln logs a debug-level message using Println.

func (*Entry) Error 

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

Error logs a error-level message using Println.

func (*Entry) Errorf 

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

Errorf logs a error-level message using Printf.

func (*Entry) Errorln 

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

Errorln logs a error-level message using Println.

func (*Entry) Fatal 

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

Fatal logs a fatal-level message using Println.

func (*Entry) Fatalf 

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

Fatalf logs a fatal-level message using Printf.

func (*Entry) Fatalln 

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

Fatalln logs a fatal-level message using Println.

func (*Entry) Info 

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

Info logs a info-level message using Println.

func (*Entry) Infof 

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

Infof logs a info-level message using Printf.

func (*Entry) Infoln 

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

Infoln logs a info-level message using Println.

func (*Entry) Panic 

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

Panic logs a panic-level message using Println.

func (*Entry) Panicf 

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

Panicf logs a panic-level message using Printf.

func (*Entry) Panicln 

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

Panicln logs a panic-level message using Println.

func (*Entry) Print 

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

Print logs a info-level message using Println.

func (*Entry) Printf 

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

Printf logs a info-level message using Printf.

func (*Entry) Println 

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

Println logs a info-level message using Println.

func (*Entry) String 

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

String returns the string representation from the reader and ultimately the formatter.

func (*Entry) Warn 

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

Warn logs a warn-level message using Println.

func (*Entry) Warnf 

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

Warnf logs a warn-level message using Printf.

func (*Entry) Warning 

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

Warning logs a warn-level message using Println.

func (*Entry) Warningf 

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

Warningf logs a warn-level message using Printf.

func (*Entry) Warningln 

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

Warningln logs a warn-level message using Println.

func (*Entry) Warnln 

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

Warnln logs a warn-level message using Println.

func (*Entry) WithError 

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

WithError 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

WithField add a single field to the Entry.

func (*Entry) WithFields 

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

WithFields adds a map of fields to the Entry.

func (*Entry) WithTime 

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

WithTime overrides the time of the Entry.

func (*Entry) Writer 

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

Writer returns an info-level log writer.

func (*Entry) WriterLevel 

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

WriterLevel returns a log writer with a specified leve.

type FieldLabel 

type FieldLabel string

FieldLabel is a type for defining label keys.

type FieldLogger 

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 

type FieldMap map[FieldLabel]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
}

Hook defines 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 {
	// Force disabling colors.
	DisableTTY bool

	// Set to true to bypass checking for a TTY before outputting colors.
	ForceTTY bool

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

	// DisableCaller controls caller logging.
	DisableCaller bool

	// DisableHostname controls hostname logging.
	DisableHostname bool

	// DisableLevel controls level logging.
	DisableLevel bool

	// DisableMessage controls message logging.
	DisableMessage bool

	// DisableTimestamp controls timestamp logging.
	DisableTimestamp bool

	// FieldMap allows users to customize the names of keys for default fields.
	// As an example:
	//  formatter := &JSONFormatter{FieldMap: FieldMap{
	//      LabelTime:  "@timestamp",
	//      LabelLevel: "@level",
	//      LabelMsg:   "@message",
	//  }}
	FieldMap FieldMap

	// TimestampFormat sets the format used for marshaling timestamps.
	TimestampFormat string

	sync.Once
	// contains filtered or unexported fields
}

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 `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 `New()`.

func GetLevel 

func GetLevel() Level

GetLevel returns the standard logger level.

func ParseLevel 

func ParseLevel(lvl string) (Level, error)

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

func (Level) String 

func (level Level) String() string

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

type LevelHooks 

type LevelHooks map[Level][]Hook

LevelHooks is an internal type for storing the hooks on a logger instance.

func (LevelHooks) Add 

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 

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 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) `log.Info`, which allows Info(), Warn(), Error() and Fatal() to be
	// logged.
	Level Level
	// contains filtered or unexported fields
}

Logger defines properties for managing logs and implements the std.Logger interface.

func New 

func New() *Logger

New 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: log.DebugLevel,
}

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

func StandardLogger 

func StandardLogger() *Logger

StandardLogger returns the Logger pointer.

func (*Logger) AddHook 

func (logger *Logger) AddHook(hook Hook)

AddHook adds a hook to the stack.

func (*Logger) Debug 

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

Debug logs a debug-level message using Println.

func (*Logger) Debugf 

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

Debugf logs a debug-level message using Printf.

func (*Logger) Debugln 

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

Debugln logs a debug-level message using Println.

func (*Logger) Error 

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

Error logs a error-level message using Println.

func (*Logger) Errorf 

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

Errorf logs a error-level message using Printf.

func (*Logger) Errorln 

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

Errorln logs a error-level message using Println.

func (*Logger) Fatal 

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

Fatal logs a fatal-level message using Println.

func (*Logger) Fatalf 

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

Fatalf logs a fatal-level message using Printf.

func (*Logger) Fatalln 

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

Fatalln logs a fatal-level message using Println.

func (*Logger) Info 

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

Info logs a info-level message using Println.

func (*Logger) Infof 

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

Infof logs a info-level message using Printf.

func (*Logger) Infoln 

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

Infoln logs a info-level message using Println.

func (*Logger) Panic 

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

Panic logs a panic-level message using Println.

func (*Logger) Panicf 

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

Panicf logs a panic-level message using Printf.

func (*Logger) Panicln 

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

Panicln logs a panic-level message using Println.

func (*Logger) Print 

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

Print logs a info-level message using Println.

func (*Logger) Printf 

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

Printf logs a info-level message using Printf.

func (*Logger) Println 

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

Println logs a info-level message using Println.

func (*Logger) SetLevel 

func (logger *Logger) SetLevel(level Level)

SetLevel sets the minimum logging level.

func (*Logger) SetNoLock 

func (logger *Logger) SetNoLock()

SetNoLock disables locking. 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 

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

SetOutput sets the logger output writer.

func (*Logger) Warn 

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

Warn logs a warn-level message using Println.

func (*Logger) Warnf 

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

Warnf logs a warn-level message using Printf.

func (*Logger) Warning 

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

Warning logs a warn-level message using Println.

func (*Logger) Warningf 

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

Warningf logs a warn-level message using Printf.

func (*Logger) Warningln 

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

Warningln logs a warn-level message using Println.

func (*Logger) Warnln 

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

Warnln logs a warn-level message using Println.

func (*Logger) WithError 

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

WithError adds 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

WithField 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

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

func (*Logger) WithTime 

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

WithTime overrides the time of the log entry.

func (*Logger) Writer 

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

Writer returns an info-level log writer.

func (*Logger) WriterLevel 

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

WriterLevel returns a log writer with a specified leve.

type MutexWrap 

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

MutexWrap contains the mutex lock.

func (*MutexWrap) Disable 

func (mw *MutexWrap) Disable()

Disable disables mutex locking.

func (*MutexWrap) Lock 

func (mw *MutexWrap) Lock()

Lock locks the mutex.

func (*MutexWrap) Unlock 

func (mw *MutexWrap) Unlock()

Unlock unlocks the mutex.

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

type Termios 

type Termios unix.Termios

Termios contains the unix Termios value.

type TextFormatter 

type TextFormatter struct {
	// Disable caller data.
	DisableCaller bool

	// Disable hostname logging.
	DisableHostname bool

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

	// Force disabling colors.
	DisableTTY bool

	// FieldMap allows users to customize the names of keys for default fields.
	// For example:
	// 	formatter := &TextFormatter{FieldMap: FieldMap{
	//      LabelCaller: "@caller",
	//      LabelData:   "@data",
	//      LabelHost:   "@hostname",
	//      LabelLevel:  "@loglevel",
	//      LabelMsg:    "@message",
	//      LabelTime:   "@timestamp",
	// 	}}
	FieldMap FieldMap

	// Set to true to bypass checking for a TTY before outputting colors.
	ForceTTY bool

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

	sync.Once
	// 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

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