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supervisor.go
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supervisor.go
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// Copyright 2014. All rights reserved.
// Use of this source code is governed by a GPLv3
// Author: Wenming Zhang <zhgwenming@gmail.com>
package nestor
import (
"fmt"
"os"
"os/signal"
"syscall"
"time"
)
const (
ENV_SUPERVISOR = "__GO_SUPERVISOR_MODE"
)
var (
DefaultSupervisor = NewSupervisor()
)
type Supervisor struct {
*Daemon
}
func NewSupervisor() *Supervisor {
d := NewDaemon()
return &Supervisor{d}
}
func (s *Supervisor) startWorker() {
cmd := s.Command
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
if err := cmd.Start(); err == nil {
log.Printf("- Started worker as pid %d\n", cmd.Process.Pid)
} else {
log.Printf("error to start worker - %s\n", err)
os.Exit(1)
}
for sig := range s.Signalc {
log.Printf("monitor captured %v\n", sig)
if sig == syscall.SIGCHLD {
break
}
// only exit if we got a TERM signal
if sig == syscall.SIGTERM {
cmd.Process.Signal(sig)
os.Exit(0)
}
}
if err := cmd.Wait(); err != nil {
log.Printf("worker[%d] exited with - %s\n", cmd.Process.Pid, err)
}
}
func (s *Supervisor) supervise() {
signal.Notify(s.Signalc,
syscall.SIGCHLD)
// process manager
for {
startTime := time.Now()
s.startWorker()
for {
endTime := time.Now()
duration := endTime.Sub(startTime)
seconds := duration.Seconds()
// restart for every 5s
if seconds > 5 {
break
} else {
time.Sleep(time.Second)
}
}
log.Printf("restarting worker\n")
}
}
func (s *Supervisor) Sink() error {
mode := os.Getenv(ENV_SUPERVISOR)
switch mode {
case "":
if err := s.Daemon.Sink(); err != nil {
return err
}
// as a foreground process, but give daemon a chance to
// setup signal/pid related things
if s.Foreground {
return nil
}
// we should be session leader here
if err := os.Setenv(ENV_SUPERVISOR, "worker"); err != nil {
fatal(err)
}
s.supervise()
log.Fatal("BUG, supervisor should loop forever") //should never get here
case "worker":
if err := unsetenv(ENV_SUPERVISOR); err != nil {
fatal(err)
}
default:
err := fmt.Errorf("critical error, unknown mode: %s", mode)
fmt.Println(err)
log.Println(err)
os.Exit(1)
}
return nil
}
func Handle(pidfile string, foreground bool, h Handler) SinkServer {
DefaultSupervisor.h = h
DefaultSupervisor.PidFile = pidfile
DefaultSupervisor.Foreground = foreground
return DefaultSupervisor
}
func HandleFunc(pidfile string, foreground bool, f func()) SinkServer {
h := HandlerFunc(f)
return Handle(pidfile, foreground, h)
}