log

package module
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 Go to latest Published: Nov 11, 2019 License: MIT Imports: 10 Imported by: 0

README

Log

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This is the simplest logging for Go.

Level Management

Use the level package and MinLevel/SetMinLevel.

// Set minimum level Warn to default logger.
log.SetMinLevel(level.Warn)

log.Debug("debug") // Output nothing
log.Warn("warn") // Output `warn`

Output Format Customization

You can customize the output format easily. Let's use Format/SetFormat to set the output format into the logger.

SetFormat(format.JSON)
logger.Info("info")
// Output:
// {"level":"INFO","message":"info","time":"2019-10-22T16:50:17.637733482+09:00"}

SetFormat(format.JSONPretty)
logger.Info("info")
// Output:
// {
//   "level": "INFO",
//   "message": "info",
//   "time": "2019-10-22T16:49:00.253014475+09:00"
// }

This repository supports only 2 formats that are plain JSON and pretty JSON.

however, you can make a new format that is along func(map[string]interface{}) string. After creating it, just needed to use Format/SetFormat to set it into the logger.

Common Output Field (Metadata)

If you use some querying service for searching specific logs like BigQuery, CloudWatch Logs Insight, Elasticsearch and other more, Metadata/SetMetadata can be used to set additional pieces of information to be able to search conveniently. For instance, Service ID, HTTP Request ID, the id of user signed in, EC2 instance-id and other more.

logger := log.New(
    log.Metadata(map[string]interface{}{
        "uesr_id":    "86f32b8b-ec0d-479f-aed1-1070aa54cecf",
        "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
    }),
    log.FlattenMetadata(true),
    log.Format(format.JSONPretty),
)

logger.Info("info")
// Output:
// {
//   "level": "INFO",
//   "message": "info",
//   "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
//   "time": "2019-10-22T17:02:02.748123389+09:00",
//   "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
// }

Example

package main

import (
    "errors"

    "github.com/kyfk/log"
    "github.com/kyfk/log/format"
    "github.com/kyfk/log/level"
)

func main() {
    logger := log.New(
        log.MinLevel(level.Warn),
        log.Format(format.JSONPretty),
        log.Metadata(map[string]interface{}{
            "service":    "book",
            "uesr_id":    "86f32b8b-ec0d-479f-aed1-1070aa54cecf",
            "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
            "path":       "/operator/hello",
            // more other metadatas
        }),
        log.FlattenMetadata(true),
    )

    logger.Debug("debug")
    logger.Info("info")
    logger.Warn("warn")
    logger.Error(errors.New("error"))
}

// Output:
//
// {
//   "level": "WARN",
//   "message": "warn",
//   "path": "/operator/hello",
//   "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
//   "service": "book",
//   "time": "2019-10-22T16:28:04.180385072+09:00",
//   "trace": [
//     "main.main /home/koya/go/src/github.com/kyfk/log/example/main.go:26",
//     "runtime.main /home/koya/go/src/github.com/golang/go/src/runtime/proc.go:203",
//     "runtime.goexit /home/koya/go/src/github.com/golang/go/src/runtime/asm_amd64.s:1357"
//   ],
//   "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
// }
// {
//   "error": "*errors.fundamental: error",
//   "level": "ERROR",
//   "path": "/operator/hello",
//   "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
//   "service": "book",
//   "time": "2019-10-22T16:28:04.180589439+09:00",
//   "trace": [
//     "main.main /home/koya/go/src/github.com/kyfk/log/example/main.go:27",
//     "runtime.main /home/koya/go/src/github.com/golang/go/src/runtime/proc.go:203",
//     "runtime.goexit /home/koya/go/src/github.com/golang/go/src/runtime/asm_amd64.s:1357"
//   ],
//   "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
// }

Documentation

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func Debug 

func Debug(v ...interface{})

Debug logs a message at level Debug on the default logger.

func Error 

func Error(err error)

Error logs a message at level Error on the default logger.

func Info 

func Info(v ...interface{})

Info logs a message at level Info on the default logger.

func SetFlattenMetadata 

func SetFlattenMetadata(b bool)

SetFlattenMetadata sets the flag if metadata is going to be flattened. If the flag is put on, metadata is going to be flattened in output

func SetFormat 

func SetFormat(fm formatter)

SetFormat sets the format of message output to the default logger.

func SetMetadata 

func SetMetadata(md map[string]interface{})

SetMetadata sets metadata to default logger. If you use some querying service for searching specific logs like BigQuery, CloudWatch Logs Insight, Elasticsearch and other more, SetMetadata can be used to set additional information to be able to search for conveniently. For instance, HTTP Request ID, the id of user signed in, EC2 instance-id and other more.

func SetMinLevel 

func SetMinLevel(lv level.Level)

SetMinLevel sets minumum logging level to the default logger.

func SetOutput 

func SetOutput(out io.Writer)

SetOutput sets io.Writer as destination of logging message to the default logger.

func SetStdLogger 

func SetStdLogger(lg *log.Logger)

SetStdLogger sets StdLogger that is used output message to the default logger.

func Warn 

func Warn(v ...interface{})

Warn logs a message at level Warn on the default logger.

Types

type Logger 

type Logger struct {
	// contains filtered or unexported fields
}

Logger has fields that Option or setter SetXXXX set.

func New 

func New(ops ...Option) *Logger

New initialize new Logger with options.

func (*Logger) Debug 

func (l *Logger) Debug(v ...interface{})

Debug logs a message at level Debug.

func (*Logger) Debugf 

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

Debugf logs a formatted message at level Debug.

func (*Logger) Error 

func (l *Logger) Error(err error)

Error logs a message at level Error.

func (*Logger) Info 

func (l *Logger) Info(v ...interface{})

Info logs a message at level Info.

func (*Logger) Infof 

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

Infof logs a formatted message at level Info.

func (*Logger) SetMetadata 

func (l *Logger) SetMetadata(meta map[string]interface{})

SetMetadata sets a metadata to a logger.

func (*Logger) Warn 

func (l *Logger) Warn(v ...interface{})

Warn logs a message at level Warn.

func (*Logger) Warnf 

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

Warn logs a formatted message at level Warn.

type NopLogger 

type NopLogger struct{}

NopLogger just implements the below simple interface. ``` 

type Logger interface {
    Debug(v ...interface{})
    Info(v ...interface{})
    Warn(v ...interface{})
    Error(err error)
}

```

In writting tests, if you use Logger and you don't want any output, NopLogger can be used as stabs.

func (NopLogger) Debug 

func (NopLogger) Debug(v ...interface{})

Debug do nothing.

func (NopLogger) Error 

func (NopLogger) Error(err error)

Error do nothing.

func (NopLogger) Info 

func (NopLogger) Info(v ...interface{})

Info do nothing.

func (NopLogger) Warn 

func (NopLogger) Warn(v ...interface{})

Warn do nothing.

type Option 

type Option func(Logger) Logger

Option is a function for initialization in the constructor of Logger.

func FlattenMetadata 

func FlattenMetadata(b bool) Option

FlattenMetadata returns Option that sets the flag if metadata is going to be flattened. If the flag is put on, metadata is going to be flattened in output.

func Format 

func Format(fm formatter) Option

Format returns Option that sets the format of message output to a new logger.

func Metadata 

func Metadata(md map[string]interface{}) Option

Metadata sets metadata to a new logger. If you use some querying service for searching specific logs like BigQuery, CloudWatch Logs Insight, Elasticsearch and other more, SetMetadata can be used to set additional information to be able to search for conveniently. For instance, HTTP Request ID, the id of user signed in, EC2 instance-id and other more.

func MinLevel 

func MinLevel(lv level.Level) Option

MinLevel returns Option that sets minumum logging level to a new logger.

func Output 

func Output(out io.Writer) Option

Output returns Option that sets io.Writer as the destination of logging message to a new logger.

Example 
SetMinLevel(level.Debug)
SetFormat(format.JSONPretty)
SetMetadata(map[string]interface{}{
	"uesr_id":    "86f32b8b-ec0d-479f-aed1-1070aa54cecf",
	"request_id": "943ad105-7543-11e6-a9ac-65e093327849",
})
SetFlattenMetadata(true)
SetOutput(os.Stdout)

defaultLogger.nowFunc = func() time.Time { return time.Time{} }
defaultLogger.withoutTrace = true

Debug("debug")
Info("info")
Warn("warn")
Error(errors.New("error"))

Output:


{
  "level": "DEBUG",
  "message": "debug",
  "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
  "time": "0001-01-01T00:00:00Z",
  "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
}
{
  "level": "INFO",
  "message": "info",
  "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
  "time": "0001-01-01T00:00:00Z",
  "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
}
{
  "level": "WARN",
  "message": "warn",
  "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
  "time": "0001-01-01T00:00:00Z",
  "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
}
{
  "error": "*errors.errorString: error",
  "level": "ERROR",
  "request_id": "943ad105-7543-11e6-a9ac-65e093327849",
  "time": "0001-01-01T00:00:00Z",
  "uesr_id": "86f32b8b-ec0d-479f-aed1-1070aa54cecf"
}

func StdLogger 

func StdLogger(lg *log.Logger) Option

StdLogger returns Option that sets StdLogger that is used output message to a new logger.

Source Files

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