Logrus: Create custom formater

[JenneyJ]

Hi,

I've created this question in stack overflow.

What I need is formatting like
[INFO]:2018-02-25 10:42:20 - Starting Process
There is a simple way to do it ?

I use go logrus and I need to change the format of the output message, I try several of things without success

what I need is format like this with formatter of logrus

[error]: datetime -  message

What I've tried without success is this

 logger := &logrus.Logger{
        Out:   os.Stderr,
        Level: level,
        Formatter: &logrus.TextFormatter{
            DisableColors: true,
            TimestampFormat : "2006-01-02 15:04:05",
            FullTimestamp:true,

        },
    }

This produce the following

time="2018-02-25 10:42:20" level=error msg="Starting Process"

And I want it to be

[INFO]:2018-02-25 10:42:20 - Starting Process

[IceflowRE]

Yes, the documentation lacks a bit.

[JenneyJ]

@IceflowRE - if it possible can you please provide example how to do it ?
or please answer here ?
https://stackoverflow.com/questions/48971780/go-change-format-of-log-output-logrus
*
Thanks!

[stevvooe]

You can make a new object that implements Formatter (https://github.com/sirupsen/logrus/blob/master/formatter.go#L7). Alternatively, you can embed the existing logrus.TextFormatter and override the Format method:

type myFormatter struct {
  logrus.TextFormatter
}

func (f *myFormatter) Format(entry *Entry) ([]byte, error) {
  // as an example, we prepend a shamrock to all log messages
  // but you can do whatever you want here.
  return append([]byte("☘ "), f.TextFormatter.Format(entry))
}

// then use this formatter as your formatter
logger := &logrus.Logger{
  Out: os.Stderr,
  Level: level,
  Formatter: &myFormatter{logrus.TextFormatter{ /* ... use your config here ..*/ }},
}

[JenneyJ]

@stevvooe ,HI
Looks promising,

1. when I try your code I got error unresolved type Entry
2. Not enough argument to return return append([]byte("[lvl]"), f.TextFormatter.Format(entry))

Can you please assist ? Thanks!

[JenneyJ]

@stevvooe - Can you assist please ?

[dgsb]

As you are implementing this formatter outside the logrus package itself, you need to prefix those type by the package name: logrus.Entry and logrus.TextFormatter

[piquan]

For Go n00bs (like me) who come across this in the future:

@stevvooe gave a good jumping-off point, but since he was writing this off-the-cuff, the details are a little off (such as management of the error, and the use of ... in the call to append). The code I'm currently (provisionally) working with is as follows:

type myFormatter struct {
    logrus.TextFormatter
}
func (f *myFormatter) Format(entry *logrus.Entry) ([]byte, error) {
    l, e := f.TextFormatter.Format(entry)
    return append([]byte("prefix: "), l...), e
}

(Here, I always prepend prefix: regardless of whether an error was encountered. I'm not sure how necessary that is.)

[freeformz]

I'm going to close this because the accepted answer on stackoverflow is pretty complete and accurate.

[bigunyak]

Would be nice if you had an example of how to create a simple custom Formatter in the package documentation itself.
Would safe people some googling and also provide them with a authoritative example.