hashicorp/logutils

Utilities for slightly better logging in Go (Golang).

logutils

logutils is a Go package that augments the standard library "log" package to make logging a bit more modern, without fragmenting the Go ecosystem with new logging packages.

The simplest thing that could possibly work

Presumably your application already uses the default log package. To switch, you'll want your code to look like the following:

package main

import (
	"log"
	"os"

	"github.com/hashicorp/logutils"
)

func main() {
	filter := &logutils.LevelFilter{
		Levels: []logutils.LogLevel{"DEBUG", "WARN", "ERROR"},
		MinLevel: logutils.LogLevel("WARN"),
		Writer: os.Stderr,
	}
	log.SetOutput(filter)

	log.Print("[DEBUG] Debugging") // this will not print
	log.Print("[WARN] Warning") // this will
	log.Print("[ERROR] Erring") // and so will this
	log.Print("Message I haven't updated") // and so will this
}

This logs to standard error exactly like go's standard logger. Any log messages you haven't converted to have a level will continue to print as before.

logutils's Issues

Similar package / implementation

Hi, I wasn't aware of your package and have written a very similar one. https://github.com/d2g/logfilter

Not sure if you wanted to review the api style or functionality to see if you were interested in merging/pulling functionality across etc.

Would it make sense to print the stack when logging in certain levels? Ex: on error logging

I've been feeling the need to output the stack upon errors so I can quickly find the source of issues. I've been printing the stack next to the logging line but it seems like this could be automatically done by logutils based on the level. How are you guys doing this?

Log utils writer

Hi !

I'm using your log library because of it's simplicity. But I noticed that, when the writer output is a file, if the log file has been deleted during run time, there is no error returned by logutil.

Did they have any way to receive an event when the log utils cannot write in the output ?

Thx a lot

Fimeo

work for the first request but not for the next

Hi Team,

I hit a strange issues in my app. Basically it is a simple webapp. In the main function after parsing flasgs, I ran a func LoadConfig which is load env vars and initialize config including logutils. So it is set at ERROR level.

After that it will spawn server and handler as normal.

It looks like for a route the first requests (since the server has been started) the logging respect the loglevel. However after that it just print everything.

I will quickly write a proof of concept for this bug and confirm again and post the code here soon.

If log.SetPrefix() contains square brackets it breaks filtering.

log.SetPrefix("[ this will break your filtering ]")

My existing code added some extra data using SetPrefix which included square brackets. When I added logutils I noticed that it was not filtering out any log messages (I got them all regardless of their level). I changed from square to normal brackets in my SetPrefix call and it fixed it.

I don't know if you need to fix this in logutils as such, but it may be worth noting it in the docs to help others avoid having this enigmatic problem.