go-zero/core/logx

logx

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logx configurations

type LogConf struct {
	ServiceName         string              `json:",optional"`
	Mode                string              `json:",default=console,options=[console,file,volume]"`
	Encoding            string              `json:",default=json,options=[json,plain]"`
	TimeFormat          string              `json:",optional"`
	Path                string              `json:",default=logs"`
	Level               string              `json:",default=info,options=[info,error,severe]"`
	Compress            bool                `json:",optional"`
	KeepDays            int                 `json:",optional"`
	StackCooldownMillis int                 `json:",default=100"`
	MaxBackups          int                 `json:",default=0"`
	MaxSize             int                 `json:",default=0"`
	Rotation            string              `json:",default=daily,options=[daily,size]"`
}

• ServiceName: set the service name, optional. on volume mode, the name is used to generate the log files. Within rest/zrpc services, the name will be set to the name of rest or zrpc automatically.
• Mode: the mode to output the logs, default is console.
  • console mode writes the logs to stdout/stderr.
  • file mode writes the logs to the files specified by Path.
  • volume mode is used in docker, to write logs into mounted volumes.
• Encoding: indicates how to encode the logs, default is json.
  • json mode writes the logs in json format.
  • plain mode writes the logs with plain text, with terminal color enabled.
• TimeFormat: customize the time format, optional. Default is 2006-01-02T15:04:05.000Z07:00.
• Path: set the log path, default to logs.
• Level: the logging level to filter logs. Default is info.
  • info, all logs are written.
  • error, info logs are suppressed.
  • severe, info and error logs are suppressed, only severe logs are written.
• Compress: whether or not to compress log files, only works with file mode.
• KeepDays: how many days that the log files are kept, after the given days, the outdated files will be deleted automatically. It has no effect on console mode.
• StackCooldownMillis: how many milliseconds to rewrite stacktrace again. It’s used to avoid stacktrace flooding.
• MaxBackups: represents how many backup log files will be kept. 0 means all files will be kept forever. Only take effect when Rotation is size. NOTE: the level of option KeepDays will be higher. Even though MaxBackups sets 0, log files will still be removed if the KeepDays limitation is reached.
• MaxSize: represents how much space the writing log file takes up. 0 means no limit. The unit is MB. Only take effect when Rotation is size.
• Rotation: represents the type of log rotation rule. Default is daily.
  • daily rotate the logs by day.
  • size rotate the logs by size of logs.

Logging methods

type Logger interface {
	// Error logs a message at error level.
	Error(...any)
	// Errorf logs a message at error level.
	Errorf(string, ...any)
	// Errorv logs a message at error level.
	Errorv(any)
	// Errorw logs a message at error level.
	Errorw(string, ...LogField)
	// Info logs a message at info level.
	Info(...any)
	// Infof logs a message at info level.
	Infof(string, ...any)
	// Infov logs a message at info level.
	Infov(any)
	// Infow logs a message at info level.
	Infow(string, ...LogField)
	// Slow logs a message at slow level.
	Slow(...any)
	// Slowf logs a message at slow level.
	Slowf(string, ...any)
	// Slowv logs a message at slow level.
	Slowv(any)
	// Sloww logs a message at slow level.
	Sloww(string, ...LogField)
	// WithContext returns a new logger with the given context.
	WithContext(context.Context) Logger
	// WithDuration returns a new logger with the given duration.
	WithDuration(time.Duration) Logger
}

• Error, Info, Slow: write any kind of messages into logs, with like fmt.Sprint(…).
• Errorf, Infof, Slowf: write messages with given format into logs.
• Errorv, Infov, Slowv: write any kind of messages into logs, with json marshalling to encode them.
• Errorw, Infow, Sloww: write the string message with given key:value fields.
• WithContext: inject the given ctx into the log messages, typically used to log trace-id and span-id.
• WithDuration: write elapsed duration into the log messages, with key duration.

Integrating with third-party logging libs

• zap
  • implementation: https://github.com/zeromicro/zero-contrib/blob/main/logx/zapx/zap.go
  • usage example: https://github.com/zeromicro/zero-examples/blob/main/logx/zaplog/main.go
• logrus
  • implementation: https://github.com/zeromicro/zero-contrib/blob/main/logx/logrusx/logrus.go
  • usage example: https://github.com/zeromicro/zero-examples/blob/main/logx/logrus/main.go

For more libs, please implement and PR to https://github.com/zeromicro/zero-contrib

Write the logs to specific stores

logx defined two interfaces to let you customize logx to write logs into any stores.

• logx.NewWriter(w io.Writer)
• logx.SetWriter(writer logx.Writer)

For example, if we want to write the logs into kafka instead of console or files, we can do it like below:

type KafkaWriter struct {
	Pusher *kq.Pusher
}

func NewKafkaWriter(pusher *kq.Pusher) *KafkaWriter {
	return &KafkaWriter{
		Pusher: pusher,
	}
}

func (w *KafkaWriter) Write(p []byte) (n int, err error) {
	// writing log with newlines, trim them.
	if err := w.Pusher.Push(strings.TrimSpace(string(p))); err != nil {
		return 0, err
	}

	return len(p), nil
}

func main() {
	pusher := kq.NewPusher([]string{"localhost:9092"}, "go-zero")
	defer pusher.Close()

	writer := logx.NewWriter(NewKafkaWriter(pusher))
	logx.SetWriter(writer)
  
	// more code
}

Complete code: https://github.com/zeromicro/zero-examples/blob/main/logx/tokafka/main.go

Filtering sensitive fields

If we need to prevent the password fields from logging, we can do it like below:

type (
	Message struct {
		Name     string
		Password string
		Message  string
	}

	SensitiveLogger struct {
		logx.Writer
	}
)

func NewSensitiveLogger(writer logx.Writer) *SensitiveLogger {
	return &SensitiveLogger{
		Writer: writer,
	}
}

func (l *SensitiveLogger) Info(msg any, fields ...logx.LogField) {
	if m, ok := msg.(Message); ok {
		l.Writer.Info(Message{
			Name:     m.Name,
			Password: "******",
			Message:  m.Message,
		}, fields...)
	} else {
		l.Writer.Info(msg, fields...)
	}
}

func main() {
	// setup logx to make sure originalWriter not nil,
	// the injected writer is only for filtering, like a middleware.

	originalWriter := logx.Reset()
	writer := NewSensitiveLogger(originalWriter)
	logx.SetWriter(writer)

	logx.Infov(Message{
		Name:     "foo",
		Password: "shouldNotAppear",
		Message:  "bar",
	})
  
	// more code
}

Complete code: https://github.com/zeromicro/zero-examples/blob/main/logx/filterfields/main.go

More examples

https://github.com/zeromicro/zero-examples/tree/main/logx

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