Rotate log files daily in Go
part of Go Cookbook
Jul 20 2017

Why rotate log files?

If you log to a file, it’s a good idea to rotate logs to limit their size.
After rotation you can backup them up to online storage or delete them.
Rotating daily has a good balance of how often to rotate vs. how large the log file becomes.
You can write logs to stdout and use external program, like logrotate, to do the rotation.
I prefer the simplicity of handling that in my own code and Go’s io.Writer interface makes it easy to implement a re-usable file rotation package.
I did just that in filerotate (documentation).
Here’s basic use (the code):
package main

import (


func main() {
	didClose := func(path string, didRotate bool) {
		fmt.Printf("closed file '%s', didRotate: %v\n", path, didRotate)
		if didRotate {
			// here you can implement e.g. compressing a log file and
			// uploading them to s3 for long-term storage
	f, err := filerotate.NewDaily(".", "log.txt", didClose)
	if err != nil {
		log.Fatalf("filerotate.NewDaily() failed with '%s'\n", err)
	_, err = f.Write([]byte("hello"))
	if err != nil {
		log.Fatalf("f.Write() failed with '%s'\n", err)
	err = f.Close()
	if err != nil {
		log.Fatalf("f.Close() failed with '%s'\n", err)
filerotate.NewDaily() creates a io.Writer which will rotatate the file daily (using UTC time). You provide a directory where files will be stored and a file suffix.
The files will be named YYYY-MM-DD-${suffix}. For exmple: log.txt => 2024-06-14-log.txt.txt etc.
filerotate.File is io.Writer and safe to use from multiple goroutines.
In addition to Write(d []byte) it also implements a Write2(d []byte, flush bool) (string, int64, int, error). It has 2 improvements over Write:

Other real-world uses

Rotation is not limited to log files. I use it as part of poor-man’s web server analytics system.
I log info about web requests to filerotate.File using my siser simple serialization format.
When a file is rotated, I compress it, upload to backblaze for backup and delete local files older than 7 days to free up space.
I also calculate basic daily statistics and e-mail a summary to myself.
I know, I could just use Google Analytics. Advantage of my little system is that I can tailor it exactly to my needs.
For example, I don’t need 99% of functionality of Google Analytics. I just want a daily email with summary, to keep track of things with minimal effort.

Feedback about page:

Optional: your email if you want me to get back to you: