filerotate

Rotates [log] files generated by any kind of [logger] that is capable to use io.Writer in golang. Implements io.WriteCloser interface.

graph >
    A[Logger] --> B[FileRotate = io.WriteCloser] 
    subgraph rotate files
        B --> C[our.log]
        C --> D[our.log.1]
        D --> E[our.log.2]
        E --> F[our.log.3]
    end
    F --> G(delete)

Loading

Configuration

// Options
type Options struct {
  // FilePath full path to the log file (i.e our.log)
  FilePath string
  // Rotate log file count times before removing. If Rotate count is 0, old versions are removed rather than rotated, so that only our.log is present
  Rotate int
  // Size of the file to grow. When exceeded, file is rotated.
  Size uint64
  // File mode, like 0600
  Mode os.FileMode
  // LineSeparator is the separator for the rotated files content
  // If specified, rotated files will be split only when the separator is found in the
  // content of the file.
  LineSeparator []byte
}

// there are predefined line separators, but you can use your own
var (
  LineSeparatorUnix    = []byte("\n")
  LineSeparatorWindows = []byte("\r\n")
  LineSeparatorMac     = []byte("\r")
  LineSeparatorNothing = []byte{}
)

Binary vs Text

filerotate is not limited to text files and can handle writing binary files, rotated by size or size + line separator, that can be any sequence of bytes specified, not limited to "\n", "\r\n" or "\r". Splitting the files does not happen at exaclty Options.Size byte and depends on the size of the buffer provided to io.Writer.Write(buf), so that binary files may get corrupted.

Usage

package main

import (
	"log"
	"github.com/illarion/filerotate"
)

func main() {
    // Create a new file rotate
    fr, err := filerotate.New(filerotate.Options{
        FilePath: "our.log",
        Rotate:   3,
        Size:     1024,
        Mode:     0600,
        LineSeparator: filerotate.LineSeparatorUnix,
    })
    
    if err != nil {
        log.Fatal(err)
    }
   
    // Connect log to the rotating writer
    log.SetOutput(fr)

    // Write to log number of times
    for i := 0; i < 10000; i++ {
        log.Printf("Hello, world %d\n", i)
    }
}

after runing the code, you will see the following files in the director

~# go run main.go

~# ls -1
our.log
our.log.1
our.log.2
our.log.3

License

MIT (see LICENSE)