Zookeeper深入理解（三）kazoo接口

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-pip

pip 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 time

from kazoo.client import KazooClient

from kazoo.client import KazooState

def 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, time

from kazoo.client import KazooClient

from kazoo.client import KazooState

from kazoo.recipe.lock import Lock

class 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。

参考链接：

http://kazoo.readthedocs.org/en/latest/basic_usage.html

http://yunjianfei.iteye.com/blog/2164888