kazoo 0.6

Higher Level Zookeeper Client

kazoo implements a higher level API to Apache Zookeeper for Python clients.

See the full docs for more information.

License

kazoo is offered under the Apache License 2.0.

Authors

kazoo started under the Nimbus Project and through collaboration with the open-source community has been merged with code from Mozilla and the Zope Corporation.

Current Development CI Status

Changelog

0.6 (2012-09-27)

API Changes

• Node paths are assumed to be Unicode objects. Under Python 2 pure-ascii strings will also be accepted. Node values are considered bytes. The byte type is an alias for str under Python 2.

• New KeeperState.CONNECTED_RO state for Zookeeper servers connected in read-only mode.

• New NotReadOnlyCallError exception when issuing a write change against a server thats currently read-only.

Features

• Add support for Python 3.2, 3.3 and PyPy (only for the threading handler).

• Handles connecting to Zookeeper 3.4+ read-only servers.

• Automatic background scanning for a Read/Write server when connected to a server in read-only mode.

• Add new Semaphore recipe.

• Add a new retry_max_delay argument to the client and by default limit the retry delay to at most an hour regardless of exponential backoff settings.

• Add new randomize_hosts argument to KazooClient, allowing one to disable host randomization.

Bug Handling

• Fix bug with locks not handling intermediary lock contenders disappearing.

• Fix bug with set_data type check failing to catch unicode values.

• Fix bug with gevent 0.13.x backport of peekable queue.

• Fix PatientChildrenWatch to use handler specific sleep function.

0.5 (2012-09-06)

Skipping a version to reflect the magnitude of the change. Kazoo is now a pure Python client with no C bindings. This release should run without a problem on alternate Python implementations such as PyPy and Jython. Porting to Python 3 in the future should also be much easier.

Documentation

• Docs have been restructured to handle the new classes and locations of the methods from the pure Python refactor.

Bug Handling

This change may introduce new bugs, however there is no longer the possibility of a complete Python segfault due to errors in the C library and/or the C binding.

• Possible segfaults from the C lib are gone.

• Password mangling due to the C lib is gone.

• The party recipes didn’t set their participating flag to False after leaving.

Features

• New client.command and client.server_version API, exposing Zookeeper’s four letter commands and giving access to structured version information.

• Added ‘include_data’ option for get_children to include the node’s Stat object.

• Substantial increase in logging data with debug mode. All correspondence with the Zookeeper server can now be seen to help in debugging.

API Changes

• The testing helpers have been moved from testing.__init__ into a testing.harness module. The official API’s of KazooTestCase and KazooTestHarness can still be directly imported from testing.

• The kazoo.handlers.util module was removed.

• Backwards compatible exception class aliases are provided for now in kazoo exceptions for the prior C exception names.

• Unicode strings now work fine for node names and are properly converted to and from unicode objects.

• The data value argument for the create and create_async methods of the client was made optional and defaults to an empty byte string. The data value must be a byte string. Unicode values are no longer allowed and will raise a TypeError.

0.3 (2012-08-23)

API Changes

• Handler interface now has an rlock_object for use by recipes.

Bug Handling

• Fixed password bug with updated zc-zookeeper-static release, which retains null bytes in the password properly.

• Fixed reconnect hammering, so that the reconnection follows retry jitter and retry backoff’s.

• Fixed possible bug with using a threading.Condition in the set partitioner. Set partitioner uses new rlock_object handler API to get an appropriate RLock for gevent.

• Issue #17 fixed: Wrap timeout exceptions with staticmethod so they can be used directly as intended. Patch by Bob Van Zant.

• Fixed bug with client reconnection looping indefinitely using an expired session id.

0.2 (2012-08-12)

Documentation

• Fixed doc references to start_async using an AsyncResult object, it uses an Event object.

Bug Handling

• Issue #16 fixed: gevent zookeeper logging failed to handle a monkey patched logging setup. Logging is now setup such that a greenlet is used for logging messages under gevent, and the thread one is used otherwise.

• Fixed bug similar to #14 for ChildrenWatch on the session listener.

• Issue #14 fixed: DataWatch had inconsistent handling of the node it was watching not existing. DataWatch also properly spawns its _get_data function to avoid blocking session events.

• Issue #15 fixed: sleep_func for SequentialGeventHandler was not set on the class appropriately leading to additional arguments being passed to gevent.sleep.

• Issue #9 fixed: Threads/greenlets didn’t gracefully shut down. Handler now has a start/stop that is used by the client when calling start and stop that shuts down the handler workers. This addresses errors and warnings that could be emitted upon process shutdown regarding a clean exit of the workers.

• Issue #12 fixed: gevent 0.13 doesn’t use the same start_new_thread as gevent 1.0 which resulted in a fully monkey-patched environment halting due to the wrong thread. Updated to use the older kazoo method of getting the real thread module object.

API Changes

• The KazooClient handler is now officially exposed as KazooClient.handler so that the appropriate sync objects can be used by end-users.

• Refactored ChildrenWatcher used by SetPartitioner into a publicly exposed PatientChildrenWatch under recipe.watchers.

Deprecations

• connect/connect_async has been renamed to start/start_async to better match the stop to indicate connection handling. The prior names are aliased for the time being.

Recipes

• Added Barrier and DoubleBarrier implementation.

0.2b1 (2012-07-27)

Bug Handling

• ZOOKEEPER-1318: SystemError is caught and rethrown as the proper invalid state exception in older zookeeper python bindings where this issue is still valid.

• ZOOKEEPER-1431: Install the latest zc-zookeeper-static library or use the packaged ubuntu one for ubuntu 12.04 or later.

• ZOOKEEPER-553: State handling isn’t checked via this method, we track it in a simpler manner with the watcher to ensure we know the right state.

Features

• Exponential backoff with jitter for retrying commands.

• Gevent 0.13 and 1.0b support.

• Lock, Party, SetPartitioner, and Election recipe implementations.

• Data and Children watching API’s.

• State transition handling with listener registering to handle session state changes (choose to fatal the app on session expiration, etc.)

• Zookeeper logging stream redirected into Python logging channel under the name ‘Zookeeper’.

• Base client library with handler support for threading and gevent async environments.