Python编写memcached启动脚本代码实例_Python

memcached是一套分布式的高速缓存系统，由LiveJournal的Brad Fitzpatrick开发，但被许多网站使用。这是一套开放源代码软件，以BSD license授权发布。

memcached缺乏认证以及安全管制，这代表应该将memcached服务器放置在防火墙后。

memcached的API使用三十二比特的循环冗余校验（CRC-32）计算键值后，将数据分散在不同的机器上。当表格满了以后，接下来新增的数据会以LRU机制替换掉。由于memcached通常只是当作缓存系统使用，所以使用memcached的应用程序在写回较慢的系统时（像是后端的数据库）需要额外的代码更新memcached内的数据。

memcached作为缓存文件服务，默认是操作系统里面是可以直接yum -y install memcached进行安装的。

/etc/init.d/memcached 是属于系统shell编写的管理脚本，下面这个脚本是python脚本编写出来的memcached管理脚本，和shell编写的脚本实现的效果一样。

代码如下

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									#!/usr/bin/python

									import sys

									import os

									from subprocess import Popen,PIPE

									class Process(object):

									  '''memached rc script'''

									  args = {'USER':'memcached',

									      'PORT':11211,

									      'MAXCONN':1024,

									      'CACHESIZE':64,

									      'OPTION':''}

									  def __init__(self,name,program,workdir):

									    self.name = name

									    self.program = program

									    self.workdir = workdir

									  def _init(self):

									    '''/var/tmp/memcached'''

									    if not os.path.exists(self.workdir):

									      os.mkdir(self.workdir)

									      os.chdir(self.workdir)

									  def _pidFile(self):

									    '''/var/tmp/memcached/memcached.pid'''

									    return os.path.join(self.workdir, "%s.pid" % self.name)

									  def _writePid(self):

									    if self.pid:

									      with open(self._pidFile(),'w') as fd:

									        fd.write(str(self.pid))

									  def _readConf(self,f):

									    with open(f) as fd:

									      lines = fd.readlines()

									      return dict([ i.strip().replace('"','').split('=') for i in lines])

									  def _parseArgs(self):

									    conf = self._readConf('/etc/sysconfig/memcached')       

									    if 'USER' in conf:

									      self.args['USER'] = conf['USER']

									    if 'PORT' in conf:

									      self.args['PORT'] = conf['PORT']

									    if 'MAXCONN' in conf:

									      self.args['MAXCONN'] = conf['MAXCONN']

									    if 'CACHESIZE' in conf:

									      self.args['CACHESIZE'] = conf['CACHESIZE']

									    options = ['-u',self.args['USER'],

									          '-p',self.args['PORT'],

									          '-m',self.args['CACHESIZE'],

									          '-c',self.args['MAXCONN']]

									    os.system("chown %s %s" % (self.args['USER'],self.workdir))

									    return options

									  def start(self):

									    pid = self._getPid()

									    if pid:

									      print "%s is running..." % self.name

									      sys.exit()

									    self._init()

									    cmd = [self.program] + self._parseArgs() + ['-d','-P',self._pidFile()]

									    p = Popen(cmd,stdout=PIPE)

									    #self.pid = p.pid

									    #self._writePid()

									    print "%s start Sucessful \t\t [OK]" % self.name

									  def _getPid(self):

									    p = Popen(['pidof',self.name],stdout=PIPE)

									    pid = p.stdout.read().strip()

									    return pid

									  def stop(self):

									    pid = self._getPid()

									    if pid:

									      os.kill(int(pid),15)

									      if os.path.exists(self._pidFile()):

									        os.remove(self._pidFile())

									      print "%s is stopped \t\t\t [OK]" % self.name

									  def restart(self):

									    self.stop()

									    self.start()

									  def status(self):

									    pid = self._getPid()

									    if pid:

									      print "%s is already running" % self.name

									    else:

									      print "%s is not running" % self.name

									  def help(self):

									    print "Usage:%s {start|stop|status|restart|} " % __file__

									def main():

									  name = 'memcached'

									  prog = '/usr/bin/memcached'

									  args = '-u nobody -p 11211 -c 1024 -m 64'

									  wd = '/var/tmp/memcached'

									  pm = Process(name = name,

									         program = prog,

									         workdir = wd)

									  try:

									    cmd = sys.argv[1]

									  except IndexError,e:

									    print "Option error"

									    sys.exit()

									  if cmd == 'start':

									    pm.start()

									  elif cmd == 'stop':

									    pm.stop()

									  elif cmd == 'restart':

									    pm.restart()

									  elif cmd == 'status':

									    pm.status()

									  else:

									    pm.help()

									if __name__ == '__main__':

									  main()