Asteria

Asteria is a logging library for go.

The most straightforward way to write a log

log.Debug("Drizzle breeze shore, dangerous night boat")
log.Error("On the moon, the willow head, after the evening")
log.WithFields(log.Fields{
    "user_id":  123,
    "username": "Tom",
}).Warningf("The gentleman is frank, the villain is often jealous.")
log.F(log.M{
    "user_id":  123,
    "username": "Tom",
}).Warningf("The gentleman is frank, the villain is often jealous.")

Log according to different modules

var logger = log.Module("asteria.user.enterprise.jobs")
   
logger.Debug("Drizzle breeze shore, dangerous night boat")
logger.Error("On the moon, the willow head, after the evening")
logger.WithFields(log.Fields{
    "user_id":  123,
    "username": "Tom",
}).Warningf("The gentleman is frank, the villain is often jealous.")
logger.F(log.M{
    "user_id":  123,
    "username": "Tom",
}).Warningf("The gentleman is frank, the villain is often jealous.")

Install

go get -u github.com/mylxsw/asteria/log

Customize

Write the line number of the file for caller

// default display file line number 
log.DefaultWithFileLine(true)
// display file line number for individual modules
log.Module("asteria").WithFileLine(true)

Filter

The filter supports separate settings for the specified module or global settings. With Filter, you can modify the log or cancel the log output before the log formatted output.

When multiple Filters are specified, multiple Filters are executed in the order they were added, and Global Filter takes precedence over a separate Filter set for the module.

Global Filter

log.AddGlobalFilter(func(filter log.Filter) log.Filter {
    return func(f formatter.Format) {
        // if f.Level == level.Debug {
        //     return
        // }
        
        f.Fields.CustomFields["user_id"] = 123
        // Not calling filter(f) will cancel the output of the log
        filter(f)
    }
})

Module Filter

var logger = log.Module("asteria")
logger.AddFilter(func(filter log.Filter) log.Filter {
    return func(f formatter.Format) {
        // filter(f)
        f.Level = level.Emergency
        filter(f)
    }
})

Log Formatter

Asteria supports custom log formats, just implement the formatter.Formatter interface.

type Formatter interface {
    Format(f Format) string
}

Three types of log formatting methods are provided by default

• text format, the default mode
• JSON with time
• JSON

Text

Use the default format, no need to make any settings, you can also specify

// Set the default module log format
log.Formatter(formatter.NewDefaultFormatter(true))
// Or
log.Default().Formatter(formatter.NewDefaultFormatter())
// Set the log format of the specified module
log.Module("asteria").Formatter(formatter.NewDefaultFormatter())

The format is as follows

[RFC3339 formatted time] [logLevel] moduleName logMessage {logContext}

The module name field is specified using the log.Module method and the default log module is automatically generated based on the package name of the caller. Context information mainly consists of two parts

• Fields starting with # are automatically set by the system
• Other fields are context information set by the user using WithFields

Sample log output

You can set the default color output by log.DefaultLogFormatter(formatter.NewDefaultFormatter(false)) or set a module to turn off color output via log.Module("asteria").Formatter(formatter.NewDefaultFormatter(false)).

Json with Time

// Set the default module log format
log.Formatter(formatter.NewJSONWithTimeFormatter())
// Or
log.Default().Formatter(formatter.NewJSONWithTimeFormatter())
// Set the log format of the specified module
log.Module("asteria").Formatter(formatter.NewJSONWithTimeFormatter())

Sample log output

[2019-07-17T16:58:24+08:00] {"module":"user","level_name":"ERROR","level":400,"context":{"#ref":"190101931","user_id":123},"message":"user create failed","datetime":"2019-07-17T16:58:24+08:00"}

Json

// Set the default module log format
log.Formatter(formatter.NewJSONFormatter())
// Or
log.Default().Formatter(formatter.NewJSONFormatter())
// Set the log format of the specified module
log.Module("asteria").Formatter(formatter.NewJSONFormatter())

Sample log output

{"module":"asteria.user.enterprise.jobs","level_name":"EMERGENCY","level":600,"context":{"#file":"/Users/mylxsw/codes/github/asteria/log_test.go","#func":"TestModule","#line":91,"#package":"github.com/mylxsw/asteria_test","#ref":"190101931","user_id":123},"message":"He remembered the count of Monte cristo","datetime":"2019-07-17T16:58:24+08:00"}

Log Writer

Asteria supports custom log output mode, only need to implement writer.Writer interface.

type Writer interface {
    Write(le level.Level, module string, message string) error
    ReOpen() error
    Close() error
}

Stdout

The default output mode is standard output, no need to make any settings, of course, you can also specify

// Set the default module log output
log.Writer(writer.NewStdoutWriter())
// can also be like this
log.Default().Writer(writer.NewStdoutWriter())
// Set the log format of the specified module
log.Module("asteria").Writer(writer.NewStdoutWriter())

File

// Set the default module log output
log.Writer(writer.NewSingleFileWriter("/var/log/asteria.log"))
// can also be like this
log.Default().Writer(writer.NewSingleFileWriter("/var/log/asteria.log"))
// Set the log format of the specified module
log.Module("asteria").Writer(writer.NewSingleFileWriter("/var/log/asteria.log"))

If you want to rotate the logs according to your own rules, such as generating new log files every day, you can use RotatingFileWriter

fw := writer.NewDefaultRotatingFileWriter(context.TODO(), func(le level.Level, module string) string {
    return fmt.Sprintf("asteria.%s.log", time.Now().Format("20060102"))
})
log.Writer(fw)

Syslog

// Set the default module log output
log.Writer(writer.NewSyslogWriter("", "", syslog.LOG_DEBUG | syslog.LOG_SYSLOG, "asteria"))
// can also be like this
log.Default().Writer(writer.NewSyslogWriter("", "", syslog.LOG_DEBUG | syslog.LOG_SYSLOG, "asteria"))
// Set the log format of the specified module
log.Module("asteria").Writer(writer.NewSyslogWriter("", "", syslog.LOG_DEBUG | syslog.LOG_SYSLOG, "asteria"))

Stream

// Set the default module log output
log.Writer(writer.NewStreamWriter(os.Stdout))
// can alse be like this
log.Default().Writer(writer.NewStreamWriter(os.Stdout))
// Set the log format of the specified module
log.Module("asteria").Writer(writer.NewStreamWriter(os.Stdout))

Stack

If you want to write the log to multiple different outputs, you can use StackWriter

m1 := writer.NewStdoutWriter()
m2 := writer.NewSyslogWriter("", "", syslog.DEBUG, "asteria")
m3 := writer.NewDefaultFileWriter("/var/log/asteria.log")

stack := writer.NewStackWriter()
// only write debug log to m1
stack.PushWithLevels(m1, level.Debug)
// only write error and emergency log to m2
stack.PushWithLevels(m2, level.Error, level.Emergency)
// all logs will write to m3
stack.PushWithLevels(m3)

log.Writer(stack)
// Or
log.Default().Writer(stack)
// Or
log.Module("asteria").Writer(stack)