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daemon.go
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daemon.go
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package immortal
import (
"bytes"
"fmt"
"io/ioutil"
"log"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"sync/atomic"
"syscall"
"time"
)
// Daemon struct
type Daemon struct {
sync.RWMutex
cfg *Config
count int
fpid bool
lock, lockOnce uint32
process *process
quit, run chan struct{}
sTime time.Time
supDir string
wg sync.WaitGroup
}
// Run returns a process instance
func (d *Daemon) Run(p Process) (*process, error) {
d.Lock()
defer d.Unlock()
var err error
// return if process is running
if atomic.SwapUint32(&d.lock, uint32(1)) != 0 {
return nil, fmt.Errorf("cannot start, process still running or waiting to be started")
}
// increment count by 1
d.count++
// to print remaininig seconds to start cmd == nil
d.process = p.GetProcess()
time.Sleep(time.Duration(d.cfg.Wait) * time.Second)
if d.process, err = p.Start(); err != nil {
atomic.StoreUint32(&d.lock, d.lockOnce)
return nil, err
}
// write parent pid
if d.cfg.Pid.Parent != "" {
if err := d.WritePid(d.cfg.Pid.Parent, os.Getpid()); err != nil {
log.Println(err)
}
}
// write child pid
if d.cfg.Pid.Child != "" {
if err := d.WritePid(d.cfg.Pid.Child, p.Pid()); err != nil {
log.Println(err)
}
}
// not following a pid
d.fpid = false
return d.process, nil
}
// WritePid write pid to file
func (d *Daemon) WritePid(file string, pid int) error {
return ioutil.WriteFile(file, []byte(fmt.Sprintf("%d", pid)), 0644)
}
// IsRunning check if process is running
func (d *Daemon) IsRunning(pid int) bool {
process, _ := os.FindProcess(pid)
if err := process.Signal(syscall.Signal(0)); err != nil {
return false
}
return true
}
// ReadPidFile read pid from file if error returns pid 0
func (d *Daemon) ReadPidFile(pidfile string) (int, error) {
content, err := ioutil.ReadFile(pidfile)
if err != nil {
return 0, err
}
pid, err := strconv.Atoi(string(bytes.TrimSpace(content)))
if err != nil {
return 0, fmt.Errorf("error parsing pid from %s: %s", pidfile, err)
}
return pid, nil
}
// New creates a new daemon
func New(cfg *Config) (*Daemon, error) {
var supDir string
// create supervise directory in specified directory
// defaults to /var/run/immortal/<app>
if cfg.ctl != "" {
supDir = cfg.ctl
} else {
// create an .immortal dir on $HOME user when calling immortal directly
// and not using immortal-dir, this helps to run immortal-ctl and
// check status of all daemons
home, err := GetUserSdir()
if err != nil {
return nil, err
}
if cfg.configFile != "" {
serviceFile := filepath.Base(cfg.configFile)
supDir = filepath.Join(home,
fmt.Sprintf("%s", strings.TrimSuffix(serviceFile, filepath.Ext(serviceFile))))
} else {
supDir = filepath.Join(home,
fmt.Sprintf("%d", os.Getpid()))
}
}
// create supervise dir
if err := os.MkdirAll(supDir, os.ModePerm); err != nil {
return nil, err
}
// lock
if lock, err := os.Create(filepath.Join(supDir, "lock")); err != nil {
return nil, err
} else if err = syscall.Flock(int(lock.Fd()), syscall.LOCK_EX+syscall.LOCK_NB); err != nil {
// resource temporarily unavailable
return nil, err
}
// remove previous socket in case exists
os.Remove(filepath.Join(supDir, "immortal.sock"))
return &Daemon{
cfg: cfg,
supDir: supDir,
quit: make(chan struct{}),
run: make(chan struct{}, 1),
sTime: time.Now(),
}, nil
}