Author: mahadev
Date: Tue Jul 27 15:11:04 2010
New Revision: 979742
URL: http://svn.apache.org/viewvc?rev=979742&view=rev
Log:
ZOOKEEPER-765. Add python example script (Travis and Andrei via mahadev)
Added:
hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/
hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/README
hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/watch_znode_for_changes.py
Modified:
hadoop/zookeeper/trunk/CHANGES.txt
Modified: hadoop/zookeeper/trunk/CHANGES.txt
URL:
http://svn.apache.org/viewvc/hadoop/zookeeper/trunk/CHANGES.txt?rev=979742&r1=979741&r2=979742&view=diff
==============================================================================
--- hadoop/zookeeper/trunk/CHANGES.txt (original)
+++ hadoop/zookeeper/trunk/CHANGES.txt Tue Jul 27 15:11:04 2010
@@ -97,6 +97,8 @@ IMPROVEMENTS:
ZOOKEEPER-821. Add ZooKeeper version information to zkpython (Rich
Schumacher via mahadev)
+ ZOOKEEPER-765. Add python example script (Travis and Andrei via mahadev)
+
NEW FEATURES:
ZOOKEEPER-729. Java client API to recursively delete a subtree.
(Kay Kay via henry)
Added: hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/README
URL:
http://svn.apache.org/viewvc/hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/README?rev=979742&view=auto
==============================================================================
--- hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/README (added)
+++ hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/README Tue Jul 27
15:11:04 2010
@@ -0,0 +1,8 @@
+
+This folder contains sample showing how you can use ZooKeeper from Python.
+
+You should also check the following projects:
+
+* http://github.com/phunt/zk-smoketest
+* http://github.com/henryr/pyzk-recipes
+
Added:
hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/watch_znode_for_changes.py
URL:
http://svn.apache.org/viewvc/hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/watch_znode_for_changes.py?rev=979742&view=auto
==============================================================================
---
hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/watch_znode_for_changes.py
(added)
+++
hadoop/zookeeper/trunk/src/contrib/zkpython/src/examples/watch_znode_for_changes.py
Tue Jul 27 15:11:04 2010
@@ -0,0 +1,202 @@
+#!/usr/bin/env python2.6
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+
+# http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+""" ZNode Change Watcher Skeleton Script
+
+This script shows you how to write a python program that watches a specific
+znode for changes and reacts to them.
+
+Steps to understand how this script works:
+
+1. start a standalone ZooKeeper server (by default it listens on
localhost:2181)
+
+Did you know you can deploy "local clusters" by using zkconf[1]?
+[1] http://github.com/phunt/zkconf
+
+2. enter the command line console
+
+3. create the test node:
+ [zk: (CONNECTED) 1] create /watch-test dummy-data
+ Created /watch-test
+
+4. in another shell start this script in verbose mode
+ $ python watch_znode_for_changes.py -v
+
+ # you should see a lot of log messages. have a look over them because
+ # you can easily understand how zookeeper works
+
+5. update the node data:
+
+ [zk: (CONNECTED) 2] set /watch-test new-data
+ cZxid = 0xa0000001a
+ ctime = Fri Jul 09 19:14:45 EEST 2010
+ mZxid = 0xa0000001e
+ mtime = Fri Jul 09 19:18:18 EEST 2010
+ pZxid = 0xa0000001a
+ cversion = 0
+ dataVersion = 1
+ aclVersion = 0
+ ephemeralOwner = 0x0
+ dataLength = 8
+ numChildren = 0
+
+ ... and you should see similar log messages:
+
+ 2010-07-09
19:18:18,537:11542(0xb6ea5b70):zoo_de...@process_completions@1765: Calling a
watcher for node [/watch-test], type = -1 event=ZOO_CHANGED_EVENT
+ 2010-07-09 19:18:18,537 watch_znode_for_changes.py:83 - Running watcher:
zh=0 event=3 state=3 path=/watch-test
+ 2010-07-09 19:18:18,537:11542(0xb6ea5b70):zoo_de...@zoo_awget@2400:
Sending request xid=0x4c374b33 for path [/watch-test] to 127.0.0.1:2181
+ 2010-07-09
19:18:18,545:11542(0xb76a6b70):zoo_de...@zookeeper_process@1980: Queueing
asynchronous response
+ 2010-07-09
19:18:18,545:11542(0xb6ea5b70):zoo_de...@process_completions@1772: Calling
COMPLETION_DATA for xid=0x4c374b33 rc=0
+ 2010-07-09 19:18:18,545 watch_znode_for_changes.py:54 - This is where your
application does work.
+
+ You can repeat this step multiple times.
+
+6. that's all. in the end you can delete the node and you should see a
ZOO_DELETED_EVENT
+
+"""
+
+import logging
+import logging.handlers
+import signal
+import sys
+import time
+import threading
+import zookeeper
+
+from optparse import OptionParser
+
+logger = logging.getLogger()
+
+class MyClass(threading.Thread):
+ znode = '/watch-test'
+
+ def __init__(self, options, args):
+ threading.Thread.__init__(self)
+
+ logger.debug('Initializing MyClass thread.')
+ if options.verbose:
+ zookeeper.set_debug_level(zookeeper.LOG_LEVEL_DEBUG)
+
+ self.zh = zookeeper.init(options.servers)
+ if zookeeper.OK != zookeeper.aget(self.zh, self.znode,
+ self.watcher, self.handler):
+ logger.critical('Unable to get znode! Exiting.')
+ sys.exit(1)
+
+ def __del__(self):
+ zookeeper.close(self.zh)
+
+ def aget(self):
+ return zookeeper.aget(self.zh, self.znode, self.watcher, self.handler)
+
+ def handler(self, zh, rc, data, stat):
+ """Handle zookeeper.aget() responses.
+
+ This code handles the zookeeper.aget callback. It does not handle watches.
+
+ Numeric arguments map to constants. See ``DATA`` in ``help(zookeeper)``
+ for more information.
+
+ Args:
+ zh Zookeeper handle that made this request.
+ rc Return code.
+ data Data stored in the znode.
+
+ Does not provide a return value.
+ """
+ if zookeeper.OK == rc:
+ logger.debug('This is where your application does work.')
+ else:
+ if zookeeper.NONODE == rc:
+ # avoid sending too many requests if the node does not yet exists
+ logger.info('Node not found. Trying again to set the watch.')
+ time.sleep(1)
+
+ if zookeeper.OK != self.aget():
+ logger.critical('Unable to get znode! Exiting.')
+ sys.exit(1)
+
+ def watcher(self, zh, event, state, path):
+ """Handle zookeeper.aget() watches.
+
+ This code is called when a znode changes and triggers a data watch.
+ It is not called to handle the zookeeper.aget call itself.
+
+ Numeric arguments map to constants. See ``DATA`` in ``help(zookeeper)``
+ for more information.
+
+ Args:
+ zh Zookeeper handle that set this watch.
+ event Event that caused the watch (often called ``type`` elsewhere).
+ state Connection state.
+ path Znode that triggered this watch.
+
+ Does not provide a return value.
+ """
+ out = ['Running watcher:',
+ 'zh=%d' % zh,
+ 'event=%d' % event,
+ 'state=%d' % state,
+ 'path=%s' % path]
+ logger.debug(' '.join(out))
+ if event == zookeeper.CHANGED_EVENT and \
+ state == zookeeper.CONNECTED_STATE and \
+ self.znode == path:
+ if zookeeper.OK != self.aget():
+ logger.critical('Unable to get znode! Exiting.')
+ sys.exit(1)
+
+ def run(self):
+ while True:
+ time.sleep(86400)
+
+
+def main(argv=None):
+ # Allow Ctrl-C
+ signal.signal(signal.SIGINT, signal.SIG_DFL)
+
+ parser = OptionParser()
+ parser.add_option('-v', '--verbose',
+ dest='verbose',
+ default=False,
+ action='store_true',
+ help='Verbose logging. (default: %default)')
+ parser.add_option('-s', '--servers',
+ dest='servers',
+ default='localhost:2181',
+ help='Comma-separated list of host:port pairs. (default: %default)')
+
+ (options, args) = parser.parse_args()
+
+ if options.verbose:
+ logger.setLevel(logging.DEBUG)
+ else:
+ logger.setLevel(logging.INFO)
+
+ formatter = logging.Formatter("%(asctime)s %(filename)s:%(lineno)d -
%(message)s")
+ stream_handler = logging.StreamHandler()
+ stream_handler.setFormatter(formatter)
+ logger.addHandler(stream_handler)
+
+ logger.info('Starting Zookeeper python example: %s' % ' '.join(sys.argv))
+
+ mc = MyClass(options, args)
+ mc.start()
+ mc.join()
+
+
+if __name__ == '__main__':
+ main()
