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Python编写memcached启动脚本代码实例

    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

    
    #!/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()

    以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持lingkb。