Zookeeper接口kazoo实例解析

技术  /  管理员 发布于 7年前   208

本文主要研究的是Zookeeper接口kazoo的相关内容，具体介绍如下。

zookeeper的开发接口以前主要以java和c为主，随着python项目越来越多的使用zookeeper作为分布式集群实现，python的zookeeper接口也出现了很多，现在主流的纯python的zookeeper接口是kazoo。因此如何使用kazoo开发基于python的分布式程序是必须掌握的。

1.安装kazoo

yum install python-pippip install kazoo

安装过程中会出现一些python依赖包未安装的情况，安装即可。

2.运行kazoo基础例子kazoo_basic.py

import timefrom kazoo.client import KazooClientfrom kazoo.client import KazooStatedef main(): zk=KazooClient(hosts='127.0.0.1:2182') zk.start()  @zk.add_listener def my_listener(state): if state == KazooState.LOST:  print("LOST") elif state == KazooState.SUSPENDED:  print("SUSPENDED") else:  print("Connected") #Creating Nodes # Ensure a path, create if necessary zk.ensure_path("/my/favorite") # Create a node with data zk.create("/my/favorite/node", b"") zk.create("/my/favorite/node/a", b"A") #Reading Data # Determine if a node exists if zk.exists("/my/favorite"): print("/my/favorite is existed") @zk.ChildrenWatch("/my/favorite/node") def watch_children(children): print("Children are now: %s" % children) # Above function called immediately, and from then on @zk.DataWatch("/my/favorite/node") def watch_node(data, stat): print("Version: %s, data: %s" % (stat.version, data.decode("utf-8"))) # Print the version of a node and its data data, stat = zk.get("/my/favorite/node") print("Version: %s, data: %s" % (stat.version, data.decode("utf-8"))) # List the children children = zk.get_children("/my/favorite/node") print("There are %s children with names %s" % (len(children), children)) #Updating Data zk.set("/my/favorite", b"some data") #Deleting Nodes zk.delete("/my/favorite/node/a") #Transactions transaction = zk.transaction() transaction.check('/my/favorite/node', version=-1) transaction.create('/my/favorite/node/b', b"B") results = transaction.commit() print ("Transaction results is %s" % results) zk.delete("/my/favorite/node/b") zk.delete("/my", recursive=True) time.sleep(2) zk.stop()if __name__ == "__main__": try: main() except Exception, ex: print "Ocurred Exception: %s" % str(ex) quit()

运行结果：

Children are now: [u'a']Version: 0, data: Version: 0, data: There are 1 children with names [u'a']Children are now: []Transaction results is [True, u'/my/favorite/node/b']Children are now: [u'b']Children are now: []No handlers could be found for logger "kazoo.recipe.watchers"LOST

以上程序运行了基本kazoo接口命令，包括创建删除加watcher等操作，通过调试并对比zookeeper服务节点znode目录结构的变化，就可以理解具体的操作结果。

3.运行通过kazoo实现的分布式锁程序kazoo_lock.py

import logging, os, timefrom kazoo.client import KazooClientfrom kazoo.client import KazooStatefrom kazoo.recipe.lock import Lockclass ZooKeeperLock(): def __init__(self, hosts, id_str, lock_name, logger=None, timeout=1): self.hosts = hosts self.id_str = id_str self.zk_client = None self.timeout = timeout self.logger = logger self.name = lock_name self.lock_handle = None self.create_lock() def create_lock(self): try: self.zk_client = KazooClient(hosts=self.hosts, logger=self.logger, timeout=self.timeout) self.zk_client.start(timeout=self.timeout) except Exception, ex: self.init_ret = False self.err_str = "Create KazooClient failed! Exception: %s" % str(ex) logging.error(self.err_str) return try: lock_path = os.path.join("/", "locks", self.name) self.lock_handle = Lock(self.zk_client, lock_path) except Exception, ex: self.init_ret = False self.err_str = "Create lock failed! Exception: %s" % str(ex) logging.error(self.err_str) return def destroy_lock(self): #self.release() if self.zk_client != None: self.zk_client.stop() self.zk_client = None def acquire(self, blocking=True, timeout=None): if self.lock_handle == None: return None try: return self.lock_handle.acquire(blocking=blocking, timeout=timeout) except Exception, ex: self.err_str = "Acquire lock failed! Exception: %s" % str(ex) logging.error(self.err_str) return None def release(self): if self.lock_handle == None: return None return self.lock_handle.release() def __del__(self): self.destroy_lock()def main(): logger = logging.getLogger() logger.setLevel(logging.INFO) sh = logging.StreamHandler() formatter = logging.Formatter('%(asctime)s -%(module)s:%(filename)s-L%(lineno)d-%(levelname)s: %(message)s') sh.setFormatter(formatter) logger.addHandler(sh) zookeeper_hosts = "127.0.0.1:2182" lock_name = "test" lock = ZooKeeperLock(zookeeper_hosts, "myid is 1", lock_name, logger=logger) ret = lock.acquire() if not ret: logging.info("Can't get lock! Ret: %s", ret) return logging.info("Get lock! Do something! Sleep 10 secs!") for i in range(1, 11): time.sleep(1) print str(i) lock.release()if __name__ == "__main__": try: main() except Exception, ex: print "Ocurred Exception: %s" % str(ex) quit()

将该测试文件copy到多个服务器，同时运行，就可以看到分布式锁的效果了。

总结

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