Python实现Daemon(守护)进程

最近在写Daemon进程，在编写过程中遇到一些小麻烦，最终还是解决了。

我编写了两种，第一种是编写了一个程序，将其用setsid命令让其放入后台运行，第二种是直接fork()一个进程，在代码里将进程设置为后台启动。

在os.sytem()函数其他外部程序时，发现os.system()是阻塞的(os.popen()也是阻塞的)，就是启动外部程序，你必须等外部程序退出，它才继续运行。用python中的subprocess库时，发现它并不阻塞主进程的运行，但是，你用外部kill命令杀死进程时，子进程会变成僵尸进程，只有父进程退出后才会退出。网上说在Windows平台下，python有个os.startfile是可以启动外部程序并不阻塞程序的运行，因为我写的Linux环境下，所以该函数不能用。最后问其他朋友，他说可以在system()将输出重定向就可以了，我试了一下，真的可以，所以现在把代码贴出了，也怪自己平常没有怎么钻。

os.system(processName+" 1>/dev/null 2>/dev/null &")

程序功能：

从配置文件读取要监控的进程，对进程实现监控，当监控程序退出时，会自动拉起进程

第一种方法：

在后台启动命令如下：setsid ./WatchProcessDog.py -m &

代码如下：

#!/usr/bin/python
#!encoding=utf-8

import ConfigParser
import sys
import threading
import time
import os
import commands
import subprocess

CONFIG_FILE = "WatchDog.ini"
SECTION="Monitor"
SECTION_KEY="Process"

class CWatchProcess(threading.Thread):
	def __init__(self,configFile):
		threading.Thread.__init__(self)
		self.thread_stop = False
		self.boolexist = False
		self.curPid = os.getpid()
		self.configFile = configFile
		cfg = ConfigParser.ConfigParser()
		try:
			cfg.read(self.configFile)
			allprocesses = cfg.get(SECTION,SECTION_KEY)
			if '#' in allprocesses:
				position1 = allprocesses.find('#')
				self.processes = allprocesses[:position1]
			else:
				self.processes = allprocesses
			self.processes = self.processes.strip()
			self.monitorProcess = self.processes.split(',')
		except Exception,e:
			print e
	def run(self):
		while not self.thread_stop:
			for tmpprocees in self.monitorProcess:
				processname = os.path.basename(tmpprocees)
				count = commands.getoutput("ps -elf | grep %s | grep -v %s | wc -l" % (processname,"grep"))
				if 0 == int(count) and "-m" == sys.argv[1]:
					self.PullProcess(tmpprocees)
					continue
				if 0 == int(count) and "-k" == sys.argv[1]:
					self.boolexist = True
					continue
				if 0 != int(count) and "-m" == sys.argv[1]:
					#print processname+" is started!"
					continue
				if 0 != int(count) and "-k" == sys.argv[1]:
					self.KillProcess(tmpprocees)
					self.boolexist = True
					continue
			if self.boolexist :
				self.KillSelf()
			time.sleep(1)
	def stop(self):
		self.thread_stop = True
	def PullProcess(self,processName):
		os.system(processName+" 1>/dev/null 2>/dev/null &")
	def KillProcess(self,processName):
		os.popen("killall %s" % os.path.basename(processName))
	def KillSelf(self):
		curNum = commands.getoutput("ps -elf | grep %s | grep -v %s | wc -l " % (sys.argv[0],"grep"))
		if 1 == curNum:
			sys.exit()
		elif 1 < curNum:
			result = os.popen("ps -elf | grep %s | grep -v %s" % (sys.argv[0],"grep")).readlines()
			for tmpresult in result:
				tmplist = tmpresult.split()
				if int(self.curPid) == int(tmplist[3]):
					continue
				else:
					os.popen("kill %s" % tmplist[3])
				#tmpcount = len(tmplist)
		sys.exit()
def main():
	count = len(sys.argv)
	if count != 2:
		help()
		sys.exit()
	if "-m" == sys.argv[1]:
		processNum = commands.getoutput("ps -elf | grep %s | grep -v %s | wc -l " % (sys.argv[0],"grep"))
		if 1 < int(processNum):
			print sys.argv[0],"is running" 
			sys.exit()
		print "start monitor processes"
	elif "-k" == sys.argv[1]:
		print "kill all processes"
	else:
		help()
		sys.exit()
def help():
	print "Usage:"
	print "./WatchProcessDog.py -m 			---monitor all processes"
	print "./WatchProcessDog.py -k 			---kill all processes"
if __name__ == "__main__":
	main()
	watchProcess = CWatchProcess(CONFIG_FILE)
	watchProcess.start()
	watchProcess.join()

第二种方法：

启动：./SqyDaemon.py -m

代码如下：

#!/usr/bin/env python
#!encoding=utf-8

import sys, os, time, atexit, string,ConfigParser,commands,subprocess
from signal import SIGTERM 

PID_FILE = "./SqyDaemon.pid"
CONFIG_FILE = "SqyDaemon.ini"
SECTION="Monitor"
SECTION_KEY="Process"

class Daemon:
	def __init__(self,configFile,pidfile):
		self.pidfile = pidfile
		self.configFile = configFile
		cfg = ConfigParser.ConfigParser()
		try:
			cfg.read(self.configFile)
			allprocesses = cfg.get(SECTION,SECTION_KEY)
			if '#' in allprocesses:
				position1 = allprocesses.find('#')
				self.processes = allprocesses[:position1]
			else:
				self.processes = allprocesses
			self.processes = self.processes.strip()
			self.monitorProcess = self.processes.split(',')
		except Exception,e:
			print e
	def _daemonize(self):
		try: 
			pid = os.fork() 
			if pid > 0:
				sys.exit(0)				#退出主进程 
		except OSError, e:
			print "fork failed!\nError is:",e.strerror
			sys.exit(1)
		os.setsid() 
		os.umask(0) 
		#创建子进程
		try: 
			pid = os.fork()
			if pid > 0:
				sys.exit(0) 
		except OSError, e: 
			print "fork failed!\nError is:",e.strerror
			sys.exit(1) 
		#创建processid文件
		atexit.register(self.delpid)
		pid = str(os.getpid())
		file(self.pidfile,'w+').write('%s\n' % pid)
	def delpid(self):
		os.remove(self.pidfile)
	def start(self):
		#检查pid文件是否存在以探测是否存在进程
		try:
			pf = file(self.pidfile,'r')
			pid = int(pf.read().strip())
			pf.close()
		except IOError:
			pid = None
		if pid:
			print "pidfile %s already exist. SqyDaemon already running?\n" % self.pidfile
			sys.exit(1)
		#启动监控
		self._daemonize()
		self._run()
	def stop(self):
		#从pid文件中获取pid
		try:
			pf = file(self.pidfile,'r')
			pid = int(pf.read().strip())
			pf.close()
		except IOError:
			pid = None
		if not pid:
			if "-r" == sys.argv[1]:
				print "SqyDaemon restart and monitor related process!"
			else :
				message = 'pidfile %s does not exist. SqyDaemon not running?\n'
				sys.stderr.write(message % self.pidfile)
			return #重启不报错
		elif "-r" == sys.argv[1]:
			print "%s is runing,now restart!" % sys.argv[0]
		elif "-k" == sys.argv[1]:
			print "all processes are killed!"
		#杀进程
		try:
			while 1:
				os.kill(pid, SIGTERM)
				time.sleep(0.1)
				for tmpprocees in self.monitorProcess:
					processname = os.path.basename(tmpprocees)
					os.system("killall %s" % processname)
		except OSError, err:
			err = str(err)
			if err.find('No such process') > 0:
				if os.path.exists(self.pidfile):
					os.remove(self.pidfile)
			else:
				print str(err)
				sys.exit(1)
	def restart(self):
		self.stop()
		self.start()
	def _run(self):
		while True:
			for tmpprocees in self.monitorProcess:
				processname = os.path.basename(tmpprocees)
				fullpath = os.path.abspath(tmpprocees)
				count = commands.getoutput("ps -elf | grep %s | grep -v %s | wc -l" % (processname,"grep"))
				if 0 == int(count):
					os.system(tmpprocees+" 1>/dev/null 2>/dev/null &") #标准输出和错误输出重定向到/dev/null
				else :
					continue
			time.sleep(2)
def help():
	print "Usage:"
	print "%s -m 			---monitor all processes" % sys.argv[0]
	print "%s -k 			---kill all processes" % sys.argv[0]
	print "%s -r 			---restart all processes" % sys.argv[0]
if __name__ == '__main__':
	daemon = Daemon(CONFIG_FILE,PID_FILE)
	if len(sys.argv) == 2:
		if '-m' == sys.argv[1]:
			daemon.start()
		elif '-k' == sys.argv[1]:
			daemon.stop()
		elif '-r' == sys.argv[1]:
			daemon.restart()
		else:
			print 'Unknown command'
			help()
			sys.exit(2)
		sys.exit(0)
	else:
		help()
		sys.exit(2)