zookeeper集群的python代码测试

上一篇已经讲解了如何安装zookeeper的python客户端，接下来是我在网上搜到的例子，举例应用环境是：

1.当有两个或者多个服务运行，并且同意时间只有一个服务接受请求(工作)，其他服务待命。

2.当接受请求(工作)的服务异常挂掉时，会从剩下的待命服务中选举出一个服务来接受请求(工作)。

下面直接上例子，有两个文件组成1.zkclient.py 2.zktest.py

# coding: utf-8
# modfied from https://github.com/phunt/zk-smoketest/blob/master/zkclient.py # zkclient.py

import zookeeper, time, threading
from collections import namedtuple

DEFAULT_TIMEOUT = 30000
VERBOSE = True

ZOO_OPEN_ACL_UNSAFE = {"perms":0x1f, "scheme":"world", "id" :"anyone"}

# Mapping of connection state values to human strings.
STATE_NAME_MAPPING = {
zookeeper.ASSOCIATING_STATE: "associating",
zookeeper.AUTH_FAILED_STATE: "auth-failed",
zookeeper.CONNECTED_STATE: "connected",
zookeeper.CONNECTING_STATE: "connecting",
zookeeper.EXPIRED_SESSION_STATE: "expired",
}

# Mapping of event type to human string.
TYPE_NAME_MAPPING = {
zookeeper.NOTWATCHING_EVENT: "not-watching",
zookeeper.SESSION_EVENT: "session",
zookeeper.CREATED_EVENT: "created",
zookeeper.DELETED_EVENT: "deleted",
zookeeper.CHANGED_EVENT: "changed",
zookeeper.CHILD_EVENT: "child",
}

class ZKClientError(Exception):
def __init__(self, value):
self.value = value
def __str__(self):
return repr(self.value)

class ClientEvent(namedtuple("ClientEvent", 'type, connection_state, path')):
"""
A client event is returned when a watch deferred fires. It denotes
some event on the zookeeper client that the watch was requested on.
"""

@property
def type_name(self):
return TYPE_NAME_MAPPING[self.type]

@property
def state_name(self):
return STATE_NAME_MAPPING[self.connection_state]

def __repr__(self):
return  "<ClientEvent %s at %r state: %s>" % (
self.type_name, self.path, self.state_name)

def watchmethod(func):
def decorated(handle, atype, state, path):
event = ClientEvent(atype, state, path)
return func(event)
return decorated

class ZKClient(object):
def __init__(self, servers, timeout=DEFAULT_TIMEOUT):
self.timeout = timeout
self.connected = False
self.conn_cv = threading.Condition( )
self.handle = -1

self.conn_cv.acquire()
if VERBOSE: print("Connecting to %s" % (servers))
start = time.time()
self.handle = zookeeper.init(servers, self.connection_watcher, timeout)
self.conn_cv.wait(timeout/1000)
self.conn_cv.release()

if not self.connected:
raise ZKClientError("Unable to connect to %s" % (servers))

if VERBOSE:
print("Connected in %d ms, handle is %d"
% (int((time.time() - start) * 1000), self.handle))

def connection_watcher(self, h, type, state, path):
self.handle = h
self.conn_cv.acquire()
self.connected = True
self.conn_cv.notifyAll()
self.conn_cv.release()

def close(self):
return zookeeper.close(self.handle)

def create(self, path, data="", flags=0, acl=[ZOO_OPEN_ACL_UNSAFE]):
start = time.time()
result = zookeeper.create(self.handle, path, data, acl, flags)
if VERBOSE:
print("Node %s created in %d ms"
% (path, int((time.time() - start) * 1000)))
return result

def delete(self, path, version=-1):
start = time.time()
result = zookeeper.delete(self.handle, path, version)
if VERBOSE:
print("Node %s deleted in %d ms"
% (path, int((time.time() - start) * 1000)))
return result

def get(self, path, watcher=None):
return zookeeper.get(self.handle, path, watcher)

def exists(self, path, watcher=None):
return zookeeper.exists(self.handle, path, watcher)

def set(self, path, data="", version=-1):
return zookeeper.set(self.handle, path, data, version)

def set2(self, path, data="", version=-1):
return zookeeper.set2(self.handle, path, data, version)

def get_children(self, path, watcher=None):
return zookeeper.get_children(self.handle, path, watcher)

def async(self, path = "/"):
return zookeeper.async(self.handle, path)

def acreate(self, path, callback, data="", flags=0, acl=[ZOO_OPEN_ACL_UNSAFE]):
result = zookeeper.acreate(self.handle, path, data, acl, flags, callback)
return result

def adelete(self, path, callback, version=-1):
return zookeeper.adelete(self.handle, path, version, callback)

def aget(self, path, callback, watcher=None):
return zookeeper.aget(self.handle, path, watcher, callback)

def aexists(self, path, callback, watcher=None):
return zookeeper.aexists(self.handle, path, watcher, callback)

def aset(self, path, callback, data="", version=-1):
return zookeeper.aset(self.handle, path, data, version, callback)

watch_count = 0

"""Callable watcher that counts the number of notifications"""
class CountingWatcher(object):
def __init__(self):
self.count = 0
global watch_count
self.id = watch_count
watch_count += 1

def waitForExpected(self, count, maxwait):
"""Wait up to maxwait for the specified count,
return the count whether or not maxwait reached.

Arguments:
- `count`: expected count
- `maxwait`: max milliseconds to wait
"""
waited = 0
while (waited < maxwait):
if self.count >= count:
return self.count
time.sleep(1.0);
waited += 1000
return self.count

def __call__(self, handle, typ, state, path):
self.count += 1
if VERBOSE:
print("handle %d got watch for %s in watcher %d, count %d" %
(handle, path, self.id, self.count))

"""Callable watcher that counts the number of notifications
and verifies that the paths are sequential"""
class SequentialCountingWatcher(CountingWatcher):
def __init__(self, child_path):
CountingWatcher.__init__(self)
self.child_path = child_path

def __call__(self, handle, typ, state, path):
if not self.child_path(self.count) == path:
raise ZKClientError("handle %d invalid path order %s" % (handle, path))
CountingWatcher.__call__(self, handle, typ, state, path)

class Callback(object):
def __init__(self):
self.cv = threading.Condition()
self.callback_flag = False
self.rc = -1

def callback(self, handle, rc, handler):
self.cv.acquire()
self.callback_flag = True
self.handle = handle
self.rc = rc
handler()
self.cv.notify()
self.cv.release()

def waitForSuccess(self):
while not self.callback_flag:
self.cv.wait()
self.cv.release()

if not self.callback_flag == True:
raise ZKClientError("asynchronous operation timed out on handle %d" %
(self.handle))
if not self.rc == zookeeper.OK:
raise ZKClientError(
"asynchronous operation failed on handle %d with rc %d" %
(self.handle, self.rc))

class GetCallback(Callback):
def __init__(self):
Callback.__init__(self)

def __call__(self, handle, rc, value, stat):
def handler():
self.value = value
self.stat = stat
self.callback(handle, rc, handler)

class SetCallback(Callback):
def __init__(self):
Callback.__init__(self)

def __call__(self, handle, rc, stat):
def handler():
self.stat = stat
self.callback(handle, rc, handler)

class ExistsCallback(SetCallback):
pass

class CreateCallback(Callback):
def __init__(self):
Callback.__init__(self)

def __call__(self, handle, rc, path):
def handler():
self.path = path
self.callback(handle, rc, handler)

class DeleteCallback(Callback):
def __init__(self):
Callback.__init__(self)

def __call__(self, handle, rc):
def handler():
pass
self.callback(handle, rc, handler)

上面的文件是别人封装好的zookeeper接口，下面是测试代码，需要依赖上面的包：

# coding: utf-8
# zktest.py

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)

下面在两台机器(也可以在同一台)上运行上面的脚本可以看到如下信息：

[2013-07-03 14:26:12,192] INFO     login ok!
Node /app/workers/worker created in 1 ms
[2013-07-03 14:26:12,195] INFO     [ worker0000000016(slave) ] register ok! I'm worker0000000016
[2013-07-03 14:26:12,196] INFO     [ worker0000000016(slave) ] /app/workers's children: ['worker0000000016']
[2013-07-03 14:26:12,196] INFO     [ worker0000000016(master) ] I've become master!

和

[2013-07-03 14:26:58,277] INFO     login ok!
Node /app/workers/worker created in 2 ms
[2013-07-03 14:26:58,281] INFO     [ worker0000000017(slave) ] register ok! I'm worker0000000017
[2013-07-03 14:26:58,282] INFO     [ worker0000000017(slave) ] /app/workers's children: ['worker0000000016', 'worker0000000017']
[2013-07-03 14:26:58,282] INFO     [ worker0000000017(slave) ] ['worker0000000016'] is masters, I'm slave

先然第一台机器做了master。

下面我们关掉第一个进程，第二台在timeout(10s)时间后,会出现如下信息：

[2013-07-03 14:28:02,204] INFO     [ worker0000000017(slave) ] child changed, try to get master again.
[2013-07-03 14:28:02,205] INFO     [ worker0000000017(slave) ] /app/workers's children: ['worker0000000017']
[2013-07-03 14:28:02,206] INFO     [ worker0000000017(master) ] I've become master!

显然，第二台机器上的程序变成了master，这就是我们想要实现的功能。

当然开启多个进程也是可以的，并且可以在程序中选择master的数量，同时本人建议timeout时间可以取小一点，我们先上环境用的是2s。

之后会更新更多zookeeper的其他应用环境的例子。