序
文主要研究一下uber的zap的NewProduction。
golang的log有zap、logrus等，不过logrus现在已经处于维护状态。
实例
SugaredLogger
func main() {
logger, _ := zap.NewProduction()
defer logger.Sync() // flushes buffer, if any
sugar := logger.Sugar()
url := "https://abc.com"
sugar.Infow("failed to fetch URL",
// Structured context as loosely typed key-value pairs.
"url", url,
"attempt", 3,
"backoff", time.Second,
)
}SugaredLogger比普通的结构化logging包快4-10倍
输出
{"level":"info","ts":1607095287.638658,"caller":"log-demo/zap_demo.go:14","msg":"failed to fetch URL","url":"https://abc.com","attempt":3,"backoff":1}Logger
func main() {
logger, _ := zap.NewProduction()
defer logger.Sync()
url := "https://abc.com"
logger.Info("failed to fetch URL",
// Structured context as strongly typed Field values.
zap.String("url", url),
zap.Int("attempt", 3),
zap.Duration("backoff", time.Second),
)
}当对性能和类型安全都要求比较高的场景就使用Logger，它比SugaredLogger速度更快，但是它只支持结构化logging
输出
{"level":"info","ts":1607095675.5623732,"caller":"log-demo/zap_demo.go:25","msg":"failed to fetch URL","url":"https://abc.com","attempt":3,"backoff":1}NewProduction
zap@v1.16.0/logger.go
func NewProduction(options ...Option) (*Logger, error) {
return NewProductionConfig().Build(options...)
}NewProduction内部执行NewProductionConfig().Build方法
NewProductionConfig
zap@v1.16.0/config.go
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"},
}
}NewProductionConfig方法按默认参数创建了Config，其中encoding为json，output为std
NewProductionEncoderConfig
zap@v1.16.0/config.go
func NewProductionEncoderConfig() zapcore.EncoderConfig {
return zapcore.EncoderConfig{
TimeKey: "ts",
LevelKey: "level",
NameKey: "logger",
CallerKey: "caller",
FunctionKey: zapcore.OmitKey,
MessageKey: "msg",
StacktraceKey: "stacktrace",
LineEnding: zapcore.DefaultLineEnding,
EncodeLevel: zapcore.LowercaseLevelEncoder,
EncodeTime: zapcore.EpochTimeEncoder,
EncodeDuration: zapcore.SecondsDurationEncoder,
EncodeCaller: zapcore.ShortCallerEncoder,
}
}NewProductionEncoderConfig这里创建了zapcore.EncoderConfig
Build
zap@v1.16.0/config.go
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
}Build方法执行cfg.buildEncoder()、cfg.openSinks()、zapcore.NewCore及New方法
New
zap@v1.16.0/logger.go
func New(core zapcore.Core, options ...Option) *Logger {
if core == nil {
return NewNop()
}
log := &Logger{
core: core,
errorOutput: zapcore.Lock(os.Stderr),
addStack: zapcore.FatalLevel + 1,
}
return log.WithOptions(options...)
}
func NewNop() *Logger {
return &Logger{
core: zapcore.NewNopCore(),
errorOutput: zapcore.AddSync(ioutil.Discard),
addStack: zapcore.FatalLevel + 1,
}
}这里对于core为nil的返回的是NewNop，否则实例化Logger；NewNop返回的logger的core为zapcore.NewNopCore()
Logger
zap@v1.16.0/logger.go
type Logger struct {
core zapcore.Core
development bool
name string
errorOutput zapcore.WriteSyncer
addCaller bool
addStack zapcore.LevelEnabler
callerSkip int
onFatal zapcore.CheckWriteAction // default is WriteThenFatal
}Logger定义了core、development、name、errorOutput、addCaller、addStack、callerSkip、onFatal属性
小结
zap.NewProduction()通过创建NewProductionEncoderConfig再Build出Logger，其中Logger的New方法主要设置了core、errorOutput、addStack属性
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