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rs committed May 13, 2017
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24 changes: 24 additions & 0 deletions .gitignore
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# Compiled Object files, Static and Dynamic libs (Shared Objects)
*.o
*.a
*.so

# Folders
_obj
_test

# Architecture specific extensions/prefixes
*.[568vq]
[568vq].out

*.cgo1.go
*.cgo2.c
_cgo_defun.c
_cgo_gotypes.go
_cgo_export.*

_testmain.go

*.exe
*.test
*.prof
10 changes: 10 additions & 0 deletions .travis.yml
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language: go
go:
- 1.7
- 1.8
- tip
matrix:
allow_failures:
- go: tip
script:
go test -v -race -cpu=1,2,4 ./...
21 changes: 21 additions & 0 deletions LICENSE
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MIT License

Copyright (c) 2017 Olivier Poitrey

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
165 changes: 165 additions & 0 deletions README.md
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# Zero Allocation JSON Logger

[![godoc](http://img.shields.io/badge/godoc-reference-blue.svg?style=flat)](https://godoc.org/github.com/rs/zerolog) [![license](http://img.shields.io/badge/license-MIT-red.svg?style=flat)](https://raw.githubusercontent.com/rs/zerolog/master/LICENSE) [![Build Status](https://travis-ci.org/rs/zerolog.svg?branch=master)](https://travis-ci.org/rs/zerolog) [![Coverage](http://gocover.io/_badge/github.com/rs/zerolog)](http://gocover.io/github.com/rs/zerolog)

The zerolog package provides a fast and simple logger dedicated to JSON output. It is inspired by uber's [zap](https://godoc.org/go.uber.org/zap) but with a mutch simpler to use API and smaller code base.

## Features

* Level logging
* Sampling
* Contextual fields

## Benchmark

All operations are allocation free:

```
BenchmarkLogEmpty-8 50000000 22 ns/op 0 B/op 0 allocs/op
BenchmarkDisabled-8 100000000 10 ns/op 0 B/op 0 allocs/op
BenchmarkInfo-8 10000000 210 ns/op 0 B/op 0 allocs/op
BenchmarkContextFields-8 10000000 254 ns/op 0 B/op 0 allocs/op
BenchmarkLogFields-8 5000000 377 ns/op 0 B/op 0 allocs/op
```

## Usage

```go
import "github.com/rs/zerolog/log"
```

### A global logger can be use for simple logging

```go
log.Info().Msg("hello world")

// Output: {"level":"info","time":1494567715,"message":"hello world"}
```

NOTE: To import the global logger, import the `log` subpackage `github.com/rs/zerolog/log`.

```go
log.Fatal().
Err(err).
Str("service", service).
Msgf("Cannot start %s", service)

// Output: {"level":"fatal","time":1494567715,"message":"Cannot start myservice","error":"some error","service":"myservice"}
// Exit 1
```

NOTE: Using `Msgf` generates an allocation even when the logger is disabled.

### Fields can be added to log messages

```go
log.Info().
Str("foo", "bar").
Int("n", 123).
Msg("hello world")

// Output: {"level":"info","time":1494567715,"foo":"bar","n":123,"message":"hello world"}
```

### Create logger instance to manage different outputs

```go
logger := zerolog.New(os.Stderr).With().Timestamp().Logger()

logger.Info().Str("foo", "bar").Msg("hello world")

// Output: {"level":"info","time":1494567715,"message":"hello world","foo":"bar"}
```

### Sub-loggers let you chain loggers with additional context

```go
sublogger := log.With().
Str("component": "foo").
Logger()
sublogger.Info().Msg("hello world")

// Output: {"level":"info","time":1494567715,"message":"hello world","component":"foo"}
```

### Level logging

```go
zerolog.GlobalLevel = zerolog.InfoLevel

log.Debug().Msg("filtered out message")
log.Info().Msg("routed message")

if e := log.Debug(); e.Enabled() {
// Compute log output only if enabled.
value := compute()
e.Str("foo": value).Msg("some debug message")
}

// Output: {"level":"info","time":1494567715,"routed message"}
```


### Customize automatic field names

```go
zerolog.TimestampFieldName = "t"
zerolog.LevelFieldName = "l"
zerolog.MessageFieldName = "m"

log.Info().Msg("hello world")

// Output: {"l":"info","t":1494567715,"m":"hello world"}
```

### Log with no level nor message

```go
log.Log().Str("foo","bar").Msg("")

// Output: {"time":1494567715,"foo":"bar"}
```

### Add contextual fields to the global logger

```go
log.Logger = log.With().Str("foo", "bar").Logger()
```

### Log Sampling

```go
sampled := log.Sample(10)
sampled.Info().Msg("will be logged every 10 messages")
```

## Global Settings

Some settings can be changed and will by applied to all loggers:

* `log.Logger`: You can set this value to customize the global logger (the one used by package level methods).
* `zerolog.GlobalLevel`: Can raise the mimimum level of all loggers. Set this to `zerolog.Disable` to disable logging altogether (quiet mode).
* `zerolog.SamplingDisable`: If set to `true`, all sampled loggers will stop sampling and issue 100% of their log events.
* `zerolog.TimestampFieldName`: Can be set to customize `Timestamp` field name.
* `zerolog.LevelFieldName`: Can be set to customize level field name.
* `zerolog.MessageFieldName`: Can be set to customize message field name.
* `zerolog.ErrorFieldName`: Can be set to customize `Err` field name.
* `zerolog.SampleFieldName`: Can be set to customize the field name added when sampling is enabled.
* `zerolog.TimeFieldFormat`: Can be set to customize `Time` field value formatting.

## Field Types

### Standard Types

* `Str`
* `Bool`
* `Int`, `Int8`, `Int16`, `Int32`, `Int64`
* `Uint`, `Uint8`, `Uint16`, `Uint32`, `Uint64`
* `Float32`, `Float64`

### Advanced Fields

* `Timestamp`: Insert UNIX timestamp field with `zerolog.TimestampFieldName` field name.
* `Time`: Add a field with the time formated with the `zerolog.TimeFieldFormat`.
* `Err`: Takes an `error` and render it as a string using the `zerolog.ErrorFieldName` field name.

72 changes: 72 additions & 0 deletions benchmark_test.go
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package zerolog

import (
"errors"
"io/ioutil"
"testing"
)

var (
errExample = errors.New("fail")
fakeMessage = "Test logging, but use a somewhat realistic message length."
)

func BenchmarkLogEmpty(b *testing.B) {
logger := New(ioutil.Discard)
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
logger.Log().Msg("")
}
})
}

func BenchmarkDisabled(b *testing.B) {
logger := New(ioutil.Discard).Level(Disabled)
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
logger.Info().Msg(fakeMessage)
}
})
}

func BenchmarkInfo(b *testing.B) {
logger := New(ioutil.Discard)
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
logger.Info().Msg(fakeMessage)
}
})
}

func BenchmarkContextFields(b *testing.B) {
logger := New(ioutil.Discard).With().
Str("string", "four!").
Str("time", "now"). // XXX
Str("duration", "123"). //XXX
Str("another string", "done!").
Logger()
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
logger.Info().Msg(fakeMessage)
}
})
}

func BenchmarkLogFields(b *testing.B) {
logger := New(ioutil.Discard)
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
logger.Info().
Str("string", "four!").
Str("time", "now"). // XXX
Str("duration", "123"). //XXX
Str("another string", "done!").
Msg(fakeMessage)
}
})
}
94 changes: 94 additions & 0 deletions context.go
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package zerolog

import "time"

// Context configures a new sub-logger with contextual fields.
type Context struct {
l Logger
}

// Logger returns the logger with the context previously set.
func (c Context) Logger() Logger {
return c.l
}

func (c Context) append(f field) Context {
return Context{
l: Logger{
parent: c.l,
w: c.l.w,
field: f.compileJSON(),
level: c.l.level,
sample: c.l.sample,
counter: c.l.counter,
},
}
}

func (c Context) Str(key, val string) Context {
return c.append(fStr(key, val))
}

func (c Context) Err(err error) Context {
return c.append(fErr(err))
}

func (c Context) Bool(key string, b bool) Context {
return c.append(fBool(key, b))
}

func (c Context) Int(key string, i int) Context {
return c.append(fInt(key, i))
}

func (c Context) Int8(key string, i int8) Context {
return c.append(fInt8(key, i))
}

func (c Context) Int16(key string, i int16) Context {
return c.append(fInt16(key, i))
}

func (c Context) Int32(key string, i int32) Context {
return c.append(fInt32(key, i))
}

func (c Context) Int64(key string, i int64) Context {
return c.append(fInt64(key, i))
}

func (c Context) Uint(key string, i uint) Context {
return c.append(fUint(key, i))
}

func (c Context) Uint8(key string, i uint8) Context {
return c.append(fUint8(key, i))
}

func (c Context) Uint16(key string, i uint16) Context {
return c.append(fUint16(key, i))
}

func (c Context) Uint32(key string, i uint32) Context {
return c.append(fUint32(key, i))
}

func (c Context) Uint64(key string, i uint64) Context {
return c.append(fUint64(key, i))
}

func (c Context) Float32(key string, f float32) Context {
return c.append(fFloat32(key, f))
}

func (c Context) Float64(key string, f float64) Context {
return c.append(fFloat64(key, f))
}

func (c Context) Timestamp() Context {
return c.append(fTimestamp())
}

func (c Context) Time(key string, t time.Time) Context {
return c.append(fTime(key, t))
}
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