golang management pidfile

Pidfile the process of storing process id. pidfile have the following effect under normal circumstances:

• Other processes can read pidfile get running process pid (of course, can also be obtained through other dynamic command)
• Before starting the process to check pidfile, prevent started several background processes (especially as the agent and the like)

Here's how docker in the management of pidfile:

package main

import (
    "fmt"
    "io/ioutil"
    "os"
    "path/filepath"
    "strings"

    log "github.com/sirupsen/logrus"
)

func main() {
    _, err := NewPIDFile("pid.file")
    if err != nil {
        log.Errorf("error to create the pid file failed:%s", err.Error())
    }
}

// PIDFile stored the process id
type PIDFile struct {
    path string
}

// just suit for linux
func processExists(pid string) bool {
    if _, err := os.Stat(filepath.Join("/proc", pid)); err == nil {
        return true
    }
    return false
}

func checkPIDFILEAlreadyExists(path string) error {
    if pidByte, err := ioutil.ReadFile(path); err == nil {
        pid := strings.TrimSpace(string(pidByte))
        if processExists(pid) {
            return fmt.Errorf("ensure the process:%s is not running pid file:%s", pid, path)
        }
    }
    return nil
}

// NewPIDFile create the pid file 
// 指定路径下生产 pidfile， 文件内容为 pid
func NewPIDFile(path string) (*PIDFile, error) {
    if err := checkPIDFILEAlreadyExists(path); err != nil {
        return nil, err
    }

    if err := os.MkdirAll(filepath.Dir(path), os.FileMode(0755)); err != nil {
        return nil, err
    }
    if err := ioutil.WriteFile(path, []byte(fmt.Sprintf("%d", os.Getpid())), 0644); err != nil {
        return nil, err
    }
    return &PIDFile{path: path}, nil
}

// Remove remove the pid file
func (file PIDFile) Remove() error {
    return os.Remove(file.path)
}

Tips:

• Different operating systems present embodiment determines whether the process is not the same. Herein is a method for detecting the process in the presence or absence of linux