Can we support pluggable interface based logger?

[gl-works]

It would be nice to use a interface based logger option with multi-level output support. The current log implementation produces too many debug logs which are rarely useful.

[slackpad]

Hi @gl-works it should be possible to support multiple levels, but there's a lot at the DEBUG level that we could probably make better use of a TRACE level for (things that are proportional to the traffic being handled).

[mofirouz]

Hi @slackpad - I'd like to bump this up as well.

We use https://github.com/uber-go/zap to take care of the application level logging and there is sadly no-way to interface with this given the current implementation.

Could you give quick yes/no on your thoughts on this, as I'm thinking of nominating myself for a PR?

[slackpad]

We are still working on standardizing the logger across our different tools so we should hold off until we figure out the direction for that. I'll update this once I have more info.

[htdvisser]

With a couple of changes it's already fine for me. The changes are compatible with the current logging, so existing code that uses memberlist does not have to be modified. I can submit a pull request if that would be appreciated.

Edit: I did remove the memberlist: prefix from log messages. If I'd put that back, it would be exactly the same as it is now.

[slackpad]

Hi @htdvisser we've now got https://github.com/hashicorp/go-hclog so we plan to port to that interface.

[htdvisser]

Ok, thanks, I'll keep an eye on that

[egourlao]

Hi, any news about the port to https://github.com/hashicorp/go-hclog? Would be happy to work on it if it's not a priority!

[etiennedi]

Here's a very dirty workaround I'm using until we get a pluggable interface logger. It's meant to work with logrus.FieldLogger, but could also be adjusted to any other logger. Maybe it'll help someone else:

type logParser struct {
	logrus logrus.FieldLogger
	regexp *regexp.Regexp
}

func newLogParser(logrus logrus.FieldLogger) *logParser {
	return &logParser{
		logrus: logrus,
		regexp: regexp.MustCompile(`(.*)\[(DEBUG|ERR|ERROR|INFO|WARNING|WARN)](.*)`),
	}
}

func (l *logParser) Write(in []byte) (int, error) {
	res := l.regexp.FindSubmatch(in)
	if len(res) != 4 {
		l.logrus.Warnf("unable to parse memberlist log message: %s", in)
	}

	switch string(res[2]) {
	case "ERR", "ERROR":
		l.logrus.Error(string(res[3]))
	case "WARN", "WARNING":
		l.logrus.Warn(string(res[3]))
	case "DEBUG":
		l.logrus.Debug(string(res[3]))
	case "INFO":
		l.logrus.Info(string(res[3]))
	default:
		l.logrus.Warnf("unable to parse memberlist log level from message: %s", in)
	}

	return len(in), nil
}

you can insert in the config using

cfg.LogOutput = newLogParser(logrus)

[kcmvp]

any update?