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go语言优秀的日志包zap预置函数用法

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zap 和 logrus 是 go 语言中日志包的佼佼者. 两者都推荐使用结构化的日志打印, 从速度上来说, zap 要比 logrus 快很多. zap 的官方案例中, 介绍了三种使用方式, 分别是 AdvancedConfiguration BasicConfiguration 和 Presets 本篇文章介绍 zap 包的 Presets 用法

Presets(预置函数) 是 zap 日志包最简单的用法, 不需要过多的自定义配置就可以用起来

NewExample

预置函数 NewExample 的源码定义如下

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func NewExample(options ...Option) *Logger {
	encoderCfg := zapcore.EncoderConfig{
		MessageKey:     "msg",
		LevelKey:       "level",
		NameKey:        "logger",
		EncodeLevel:    zapcore.LowercaseLevelEncoder,
		EncodeTime:     zapcore.ISO8601TimeEncoder,
		EncodeDuration: zapcore.StringDurationEncoder,
	}
	core := zapcore.NewCore(zapcore.NewJSONEncoder(encoderCfg), os.Stdout, DebugLevel)
	return New(core).WithOptions(options...)
}

可以看到, 预置函数为我们配置了以上内容, 包括

  • 各个字段的名称
  • 日志级别的显示形式
  • 时间编码类型
  • 序列化时间的方式
  • 输出到标准输出
  • 以json形式打印
  • 日志打印级别为Debug

NewExample 输出信息比较少, 打印内容比较详细, 一般用于开发时临时调试使用

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package main

import (
	"go.uber.org/zap"
	"time"
)

func main() {
	logger := zap.NewExample()
	defer logger.Sync()

	const url = "http://example.com"

	// sugar 版本的 logger
	sugar := logger.Sugar()
	sugar.Infow("Failed to fetch URL.",
		"url", url,
		"attempt", 3,
		"backoff", time.Second,
	)
	sugar.Infof("Failed to fetch URL: %s", url)

	// 极速版 logger
	logger.Info("Failed to fetch URL.",
		zap.String("url", url),
		zap.Int("attempt", 3),
		zap.Duration("backoff", time.Second),
	)
}

执行结果

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{"level":"info","msg":"Failed to fetch URL.","url":"http://example.com","attempt":3,"backoff":"1s"}
{"level":"info","msg":"Failed to fetch URL: http://example.com"}
{"level":"info","msg":"Failed to fetch URL.","url":"http://example.com","attempt":3,"backoff":"1s"}

NewDevelopment

预置函数 NewDevelopment 的源码定义如下

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func NewDevelopment(options ...Option) (*Logger, error) {
	return NewDevelopmentConfig().Build(options...)
}

func NewDevelopmentConfig() Config {
	return Config{
		Level:            NewAtomicLevelAt(DebugLevel),
		Development:      true,
		Encoding:         "console",
		EncoderConfig:    NewDevelopmentEncoderConfig(),
		OutputPaths:      []string{"stderr"},
		ErrorOutputPaths: []string{"stderr"},
	}
}

func NewDevelopmentEncoderConfig() zapcore.EncoderConfig {
	return zapcore.EncoderConfig{
		// Keys can be anything except the empty string.
		TimeKey:        "T",
		LevelKey:       "L",
		NameKey:        "N",
		CallerKey:      "C",
		MessageKey:     "M",
		StacktraceKey:  "S",
		LineEnding:     zapcore.DefaultLineEnding,
		EncodeLevel:    zapcore.CapitalLevelEncoder,
		EncodeTime:     zapcore.ISO8601TimeEncoder,
		EncodeDuration: zapcore.StringDurationEncoder,
		EncodeCaller:   zapcore.ShortCallerEncoder,
	}
}

func (cfg Config) Build(opts ...Option) (*Logger, error) {
	enc, err := cfg.buildEncoder()
	if err != nil {
		return nil, err
	}

	sink, errSink, err := cfg.openSinks()
	if err != nil {
		return nil, err
	}

	if cfg.Level == (AtomicLevel{}) {
		return nil, fmt.Errorf("missing Level")
	}

	log := New(
		zapcore.NewCore(enc, sink, cfg.Level),
		cfg.buildOptions(errSink)...,
	)
	if len(opts) > 0 {
		log = log.WithOptions(opts...)
	}
	return log, nil
}

NewDevelopment 打印内容比较详细(debug level), 输出格式为console

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package main

import (
	"go.uber.org/zap"
	"time"
)

func main() {
	logger, err := zap.NewDevelopment()
	if err != nil {
		panic(err)
	}
	defer logger.Sync()

	const url = "http://example.com"

	// sugar 版本的 logger
	sugar := logger.Sugar()
	sugar.Infow("Failed to fetch URL.",
		"url", url,
		"attempt", 3,
		"backoff", time.Second,
	)
	sugar.Infof("Failed to fetch URL: %s", url)

	// 极速版 logger
	logger.Info("Failed to fetch URL.",
		zap.String("url", url),
		zap.Int("attempt", 3),
		zap.Duration("backoff", time.Second),
	)
}

执行结果

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2020-03-17T22:52:45.665+0800    INFO    log/l2.go:19    Failed to fetch URL.    {"url": "http://example.com", "attempt": 3, "backoff": "1s"}
2020-03-17T22:52:45.666+0800    INFO    log/l2.go:24    Failed to fetch URL: http://example.com
2020-03-17T22:52:45.666+0800    INFO    log/l2.go:27    Failed to fetch URL.    {"url": "http://example.com", "attempt": 3, "backoff": "1s"}

NewProduction

源码如下

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 func NewProduction(options ...Option) (*Logger, error) {
	return NewProductionConfig().Build(options...)
}

func NewProductionConfig() Config {
	return Config{
		Level:       NewAtomicLevelAt(InfoLevel),
		Development: false,
		Sampling: &SamplingConfig{
			Initial:    100,
			Thereafter: 100,
		},
		Encoding:         "json",
		EncoderConfig:    NewProductionEncoderConfig(),
		OutputPaths:      []string{"stderr"},
		ErrorOutputPaths: []string{"stderr"},
	}
}

func NewProductionEncoderConfig() zapcore.EncoderConfig {
	return zapcore.EncoderConfig{
		TimeKey:        "ts",
		LevelKey:       "level",
		NameKey:        "logger",
		CallerKey:      "caller",
		MessageKey:     "msg",
		StacktraceKey:  "stacktrace",
		LineEnding:     zapcore.DefaultLineEnding,
		EncodeLevel:    zapcore.LowercaseLevelEncoder,
		EncodeTime:     zapcore.EpochTimeEncoder,
		EncodeDuration: zapcore.SecondsDurationEncoder,
		EncodeCaller:   zapcore.ShortCallerEncoder,
	}
}

func (cfg Config) Build(opts ...Option) (*Logger, error) {
	enc, err := cfg.buildEncoder()
	if err != nil {
		return nil, err
	}

	sink, errSink, err := cfg.openSinks()
	if err != nil {
		return nil, err
	}

	if cfg.Level == (AtomicLevel{}) {
		return nil, fmt.Errorf("missing Level")
	}

	log := New(
		zapcore.NewCore(enc, sink, cfg.Level),
		cfg.buildOptions(errSink)...,
	)
	if len(opts) > 0 {
		log = log.WithOptions(opts...)
	}
	return log, nil
}

NewProduction 的日志级别提高到了info level, 而且默认使用了结构化更友好的json格式输出日志, 该预置函数, 适用于生产环境, 程序上线后使用

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 func main() {
	logger, err := zap.NewProduction()
	if err != nil {
		panic(err)
	}
	defer logger.Sync()

	const url = "http://example.com"

	// sugar 版本的 logger
	sugar := logger.Sugar()
	sugar.Infow("Failed to fetch URL.",
		"url", url,
		"attempt", 3,
		"backoff", time.Second,
	)
	sugar.Infof("Failed to fetch URL: %s", url)

	// 极速版 logger
	logger.Info("Failed to fetch URL.",
		zap.String("url", url),
		zap.Int("attempt", 3),
		zap.Duration("backoff", time.Second),
	)
}

执行结果

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{"level":"info","ts":1584457473.942979,"caller":"log/l2.go:19","msg":"Failed to fetch URL.","url":"http://example.com","attempt":3,"backoff":1}
{"level":"info","ts":1584457473.943102,"caller":"log/l2.go:24","msg":"Failed to fetch URL: http://example.com"}
{"level":"info","ts":1584457473.943125,"caller":"log/l2.go:27","msg":"Failed to fetch URL.","url":"http://example.com","attempt":3,"backoff":1}
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