zookeeper python接口实例详解

本文主要讲python支持zookeeper的接口库安装和使用。zk的python接口库有zkpython，还有kazoo，下面是zkpython，是基于zk的C库的python接口。

zkpython安装

前提是zookeeper安装包已经在/usr/local/zookeeper下

cd /usr/local/zookeeper/src/c
./configure
make
make install

wget --no-check-certificate http://pypi.python.org/packages/source/z/zkpython/zkpython-0.4.tar.gz
tar -zxvf zkpython-0.4.tar.gz
cd zkpython-0.4
sudo python setup.py install

zkpython应用

下面是网上一个zkpython的类，用的时候只要import进去就行
vim zkclient.py

#!/usr/bin/env python2.7
# -*- coding: UTF-8 -*-

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)

总结

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