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zktest.py
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zktest.py
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# coding: utf-8
# zktest.py
'''
这个简单的demo所做的事情,就是通过在zookeeper的/app/workers节点下建立临时的子节点( flags=zookeeper.EPHEMERAL | zookeeper.SEQUENCE ),每次create完成之后检查自己是不是在最小的MASTERS_NUM(例子中为1,即单master)里。如果是的话,作为master运行,否则的话,作为slave运行。
这样的话,当我们的master挂掉以后,与zookeeper之间的连接也会中断,过了指定的TIMEOUT以后,master之前在worker下的子节点就会被删除,于是slave节点之前设置的watcher会被触发,再次检查自己是否为master,如果是的话则完成切换。
zkCli.sh
[zk: localhost:2181(CONNECTED) 8] ls /app/workers
[worker0000000007, worker0000000006]
'''
import logging
from os.path import basename, join
from zkclient import ZKClient, zookeeper, watchmethod
logging.basicConfig(
level = logging.DEBUG,
format = "[%(asctime)s] %(levelname)-8s %(message)s"
)
log = logging
class GJZookeeper(object):
ZK_HOST = "localhost:2181"
ROOT = "/app"
WORKERS_PATH = join(ROOT, "workers")
MASTERS_NUM = 1
TIMEOUT = 10000
def __init__(self, verbose = True):
self.VERBOSE = verbose
self.masters = []
self.is_master = False
self.path = None
self.zk = ZKClient(self.ZK_HOST, timeout = self.TIMEOUT)
self.say("login ok!")
# init
self.__init_zk()
# register
self.register()
def __init_zk(self):
"""
create the zookeeper node if not exist
"""
nodes = (self.ROOT, self.WORKERS_PATH)
for node in nodes:
if not self.zk.exists(node):
try:
self.zk.create(node, "")
except:
pass
@property
def is_slave(self):
return not self.is_master
def register(self):
"""
register a node for this worker
"""
self.path = self.zk.create(self.WORKERS_PATH + "/worker", "1", flags=zookeeper.EPHEMERAL | zookeeper.SEQUENCE)
self.path = basename(self.path)
self.say("register ok! I'm %s" % self.path)
# check who is the master
self.get_master()
def get_master(self):
"""
get children, and check who is the smallest child
"""
@watchmethod
def watcher(event):
self.say("child changed, try to get master again.")
self.get_master()
children = self.zk.get_children(self.WORKERS_PATH, watcher)
children.sort()
self.say("%s's children: %s" % (self.WORKERS_PATH, children))
# check if I'm master
self.masters = children[:self.MASTERS_NUM]
if self.path in self.masters:
self.is_master = True
self.say("I've become master!")
else:
self.say("%s is masters, I'm slave" % self.masters)
def say(self, msg):
"""
print messages to screen
"""
if self.VERBOSE:
if self.path:
if self.is_master:
log.info("[ %s(%s) ] %s" % (self.path, "master" , msg))
else:
log.info("[ %s(%s) ] %s" % (self.path, "slave", msg))
else:
log.info(msg)
def main():
gj_zookeeper = GJZookeeper()
if __name__ == "__main__":
main()
import time
time.sleep(1000)