log

package module
v1.1.0 Latest Latest
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 Go to latest Published: Jul 2, 2018 License: MIT Imports: 9 Imported by: 0

README

Structured logging for golang

Package log implements a simple structured logging API inspired by Logrus, designed with centralization in mind. Read more on Medium.

Handlers

  • cli – human-friendly CLI output
  • discard – discards all logs
  • es – Elasticsearch handler
  • graylog – Graylog handler
  • json – JSON output handler
  • kinesis – AWS Kinesis handler
  • level – level filter handler
  • logfmt – logfmt plain-text formatter
  • memory – in-memory handler for tests
  • multi – fan-out to multiple handlers
  • papertrail – Papertrail handler
  • text – human-friendly colored output
  • delta – outputs the delta between log calls and spinner

Build Status GoDoc

Documentation

Overview

Package log implements a simple structured logging API designed with few assumptions. Designed for centralized logging solutions such as Kinesis which require encoding and decoding before fanning-out to handlers.

You may use this package with inline handlers, much like Logrus, however a centralized solution is recommended so that apps do not need to be re-deployed to add or remove logging service providers.

Example (Errors)

Errors are passed to WithError(), populating the "error" field. 

package main

import (
	"errors"

	"github.com/apex/log"
)

func main() {
	err := errors.New("boom")
	log.WithError(err).Error("upload failed")
}

Output:
Example (MultipleFields)

Multiple fields can be set, via chaining, or WithFields(). 

package main

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

func main() {
	log.WithFields(log.Fields{
		"user": "Tobi",
		"file": "sloth.png",
		"type": "image/png",
	}).Info("upload")
}

Output:
Example (Structured)

Structured logging is supported with fields, and is recommended over the formatted message variants. 

package main

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

func main() {
	log.WithField("user", "Tobo").Info("logged in")
}

Output:
Example (Trace)

Trace can be used to simplify logging of start and completion events, for example an upload which may fail. 

package main

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

func main() (err error) {
	defer log.Trace("upload").Stop(&err)
	return nil
}

Output:
Example (Unstructured)

Unstructured logging is supported, but not recommended since it is hard to query. 

package main

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

func main() {
	log.Infof("%s logged in", "Tobi")
}

Output:

Index

Examples

Constants

This section is empty.

Variables

View Source 
var ErrInvalidLevel = errors.New("invalid level")

ErrInvalidLevel is returned if the severity level is invalid.

View Source 
var Now = time.Now

Now returns the current time.

Functions

func Debug 

func Debug(msg string)

Debug level message.

func Debugf 

func Debugf(msg string, v ...interface{})

Debugf level formatted message.

func Error 

func Error(msg string)

Error level message.

func Errorf 

func Errorf(msg string, v ...interface{})

Errorf level formatted message.

func Fatal 

func Fatal(msg string)

Fatal level message, followed by an exit.

func Fatalf 

func Fatalf(msg string, v ...interface{})

Fatalf level formatted message, followed by an exit.

func Info 

func Info(msg string)

Info level message.

func Infof 

func Infof(msg string, v ...interface{})

Infof level formatted message.

func SetHandler 

func SetHandler(h Handler)

SetHandler sets the handler. This is not thread-safe. The default handler outputs to the stdlib log.

func SetLevel 

func SetLevel(l Level)

SetLevel sets the log level. This is not thread-safe.

func SetLevelFromString 

func SetLevelFromString(s string)

SetLevelFromString sets the log level from a string, panicing when invalid. This is not thread-safe.

func Warn 

func Warn(msg string)

Warn level message.

func Warnf 

func Warnf(msg string, v ...interface{})

Warnf level formatted message.

Types

type Entry 

type Entry struct {
	Logger    *Logger   `json:"-"`
	Fields    Fields    `json:"fields"`
	Level     Level     `json:"level"`
	Timestamp time.Time `json:"timestamp"`
	Message   string    `json:"message"`
	// contains filtered or unexported fields
}

Entry represents a single log entry.

func NewEntry 

func NewEntry(log *Logger) *Entry

NewEntry returns a new entry for `log`.

func Trace 

func Trace(msg string) *Entry

Trace returns a new entry with a Stop method to fire off a corresponding completion log, useful with defer.

func WithError 

func WithError(err error) *Entry

WithError returns a new entry with the "error" set to `err`.

func WithField 

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

WithField returns a new entry with the `key` and `value` set.

func WithFields 

func WithFields(fields Fielder) *Entry

WithFields returns a new entry with `fields` set.

func (*Entry) Debug 

func (e *Entry) Debug(msg string)

Debug level message.

func (*Entry) Debugf 

func (e *Entry) Debugf(msg string, v ...interface{})

Debugf level formatted message.

func (*Entry) Error 

func (e *Entry) Error(msg string)

Error level message.

func (*Entry) Errorf 

func (e *Entry) Errorf(msg string, v ...interface{})

Errorf level formatted message.

func (*Entry) Fatal 

func (e *Entry) Fatal(msg string)

Fatal level message, followed by an exit.

func (*Entry) Fatalf 

func (e *Entry) Fatalf(msg string, v ...interface{})

Fatalf level formatted message, followed by an exit.

func (*Entry) Info 

func (e *Entry) Info(msg string)

Info level message.

func (*Entry) Infof 

func (e *Entry) Infof(msg string, v ...interface{})

Infof level formatted message.

func (*Entry) Stop 

func (e *Entry) Stop(err *error)

Stop should be used with Trace, to fire off the completion message. When an `err` is passed the "error" field is set, and the log level is error.

func (*Entry) Trace 

func (e *Entry) Trace(msg string) *Entry

Trace returns a new entry with a Stop method to fire off a corresponding completion log, useful with defer.

func (*Entry) Warn 

func (e *Entry) Warn(msg string)

Warn level message.

func (*Entry) Warnf 

func (e *Entry) Warnf(msg string, v ...interface{})

Warnf level formatted message.

func (*Entry) WithError 

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

WithError returns a new entry with the "error" set to `err`.

The given error may implement .Fielder, if it does the method will add all its `.Fields()` into the returned entry.

func (*Entry) WithField 

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

WithField returns a new entry with the `key` and `value` set.

func (*Entry) WithFields 

func (e *Entry) WithFields(fields Fielder) *Entry

WithFields returns a new entry with `fields` set.

type Fielder 

type Fielder interface {
	Fields() Fields
}

Fielder is an interface for providing fields to custom types.

type Fields 

type Fields map[string]interface{}

Fields represents a map of entry level data used for structured logging.

func (Fields) Fields 

func (f Fields) Fields() Fields

Fields implements Fielder.

func (Fields) Get 

func (f Fields) Get(name string) interface{}

Get field value by name.

func (Fields) Names 

func (f Fields) Names() (v []string)

Names returns field names sorted.

type Handler 

type Handler interface {
	HandleLog(*Entry) error
}

Handler is used to handle log events, outputting them to stdio or sending them to remote services. See the "handlers" directory for implementations.

It is left up to Handlers to implement thread-safety.

type HandlerFunc 

type HandlerFunc func(*Entry) error

The HandlerFunc type is an adapter to allow the use of ordinary functions as log handlers. If f is a function with the appropriate signature, HandlerFunc(f) is a Handler object that calls f.

func (HandlerFunc) HandleLog 

func (f HandlerFunc) HandleLog(e *Entry) error

HandleLog calls f(e).

type Interface 

type Interface interface {
	WithFields(fields Fielder) *Entry
	WithField(key string, value interface{}) *Entry
	WithError(err error) *Entry
	Debug(msg string)
	Info(msg string)
	Warn(msg string)
	Error(msg string)
	Fatal(msg string)
	Debugf(msg string, v ...interface{})
	Infof(msg string, v ...interface{})
	Warnf(msg string, v ...interface{})
	Errorf(msg string, v ...interface{})
	Fatalf(msg string, v ...interface{})
	Trace(msg string) *Entry
}

Interface represents the API of both Logger and Entry. 

var Log Interface = &Logger{
	Handler: HandlerFunc(handleStdLog),
	Level:   InfoLevel,
}

singletons ftw?

type Level 

type Level int

Level of severity. 

const (
	InvalidLevel Level = iota - 1
	DebugLevel
	InfoLevel
	WarnLevel
	ErrorLevel
	FatalLevel
)

Log levels.

func MustParseLevel 

func MustParseLevel(s string) Level

MustParseLevel parses level string or panics.

func ParseLevel 

func ParseLevel(s string) (Level, error)

ParseLevel parses level string.

func (Level) MarshalJSON 

func (l Level) MarshalJSON() ([]byte, error)

MarshalJSON implementation.

func (Level) String 

func (l Level) String() string

String implementation.

func (*Level) UnmarshalJSON 

func (l *Level) UnmarshalJSON(b []byte) error

UnmarshalJSON implementation.

type Logger 

type Logger struct {
	Handler Handler
	Level   Level
}

Logger represents a logger with configurable Level and Handler.

func (*Logger) Debug 

func (l *Logger) Debug(msg string)

Debug level message.

func (*Logger) Debugf 

func (l *Logger) Debugf(msg string, v ...interface{})

Debugf level formatted message.

func (*Logger) Error 

func (l *Logger) Error(msg string)

Error level message.

func (*Logger) Errorf 

func (l *Logger) Errorf(msg string, v ...interface{})

Errorf level formatted message.

func (*Logger) Fatal 

func (l *Logger) Fatal(msg string)

Fatal level message, followed by an exit.

func (*Logger) Fatalf 

func (l *Logger) Fatalf(msg string, v ...interface{})

Fatalf level formatted message, followed by an exit.

func (*Logger) Info 

func (l *Logger) Info(msg string)

Info level message.

func (*Logger) Infof 

func (l *Logger) Infof(msg string, v ...interface{})

Infof level formatted message.

func (*Logger) Trace 

func (l *Logger) Trace(msg string) *Entry

Trace returns a new entry with a Stop method to fire off a corresponding completion log, useful with defer.

func (*Logger) Warn 

func (l *Logger) Warn(msg string)

Warn level message.

func (*Logger) Warnf 

func (l *Logger) Warnf(msg string, v ...interface{})

Warnf level formatted message.

func (*Logger) WithError 

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

WithError returns a new entry with the "error" set to `err`.

func (*Logger) WithField 

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

WithField returns a new entry with the `key` and `value` set.

Note that the `key` should not have spaces in it - use camel case or underscores

func (*Logger) WithFields 

func (l *Logger) WithFields(fields Fielder) *Entry

WithFields returns a new entry with `fields` set.

Source Files

View all Source files

Directories

Path Synopsis
_examples
cli
default
delta
es
json
kinesis
logfmt
multi
stack
text
trace
handlers
cli
Package cli implements a colored text handler suitable for command-line interfaces.
 Package cli implements a colored text handler suitable for command-line interfaces.
delta
Package delta provides a log handler which times the delta between each log call, useful for debug output for command-line programs.
 Package delta provides a log handler which times the delta between each log call, useful for debug output for command-line programs.
discard
Package discard implements a no-op handler useful for benchmarks and tests.
 Package discard implements a no-op handler useful for benchmarks and tests.
es
Package es implements an Elasticsearch batch handler.
 Package es implements an Elasticsearch batch handler.
graylog
Package implements a Graylog-backed handler.
 Package implements a Graylog-backed handler.
json
Package json implements a JSON handler.
 Package json implements a JSON handler.
kinesis
level
Package level implements a level filter handler.
 Package level implements a level filter handler.
logfmt
Package logfmt implements a "logfmt" format handler.
 Package logfmt implements a "logfmt" format handler.
memory
Package memory implements an in-memory handler useful for testing, as the entries can be accessed after writes.
 Package memory implements an in-memory handler useful for testing, as the entries can be accessed after writes.
multi
Package multi implements a handler which invokes a number of handlers.
 Package multi implements a handler which invokes a number of handlers.
papertrail
Package papertrail implements a papertrail logfmt format handler.
 Package papertrail implements a papertrail logfmt format handler.
text
Package text implements a development-friendly textual handler.
 Package text implements a development-friendly textual handler.

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