nd_service_registry 0.2.1

Installation

To install, run

python setup.py install

or

pip install nd_service_registry

Instantiating a KazooServiceRegistry module

Create a logger object:

>>> import logging
>>> logger = logging.getLogger()
>>> logger.setLevel(logging.DEBUG)
>>> handler = logging.StreamHandler()
>>> logger.addHandler(handler)

To create your initial connection object:

>>> from nd_service_registry import KazooServiceRegistry
>>> nd = KazooServiceRegistry()

The KazooServiceRegistry object is a child of nd_service_registry that conforms to our ServiceRegistry specs, whlie leveraging Kazoo as the backend. The object handles all of your connection states - there is no need to start/stop or monitor the connection state at all.

Basic use

To register the host as providing a particular service:

>>> nd.set_node('/services/ssh/server1:22', data={ 'foo': 'bar'})

Getting a list of servers at a path:

>>> nd.get('/services/ssh')
{'children': {u'server1:22': {u'foo': u'bar',
                              u'created': u'2012-12-15 00:45:03',
                              u'pid': 10733}},
 'data': None,
 'path': '/services/ssh',
 'stat': ZnodeStat(czxid=6, mzxid=6, ctime=1355532303688,
                   mtime=1355532303688, version=0, cversion=1,
                   aversion=0, ephemeralOwner=0, dataLength=0,
                   numChildren=1, pzxid=7)}

Failure Handling

The goal of this module is to be as self-contained as possible and require as little code in your app as possible. To that end, we almost never raise an Exception once the module is loaded up and connected.

We do raise a few exceptions, and each one is documented here. Whenever we can though, we instead just return False as a way of indicating that we were unable to perform your command now … but that we will take care of it later. Whenever we do this, we throw a WARNING log message as well.

nd_service_registry.exceptions.NoConnection

Thrown if you attempt any operation that requires immediate access to the backend Zookeeper service. Either a set() operation, or a get() operation on a path for the first time.

Also thrown during initial connection to Zookeeper, if lazy=False.

(It should be noted, a get() will actually return the cached results even if Zookeeper is down. This allows the service to fail temporarily in the background but your app is still able to get the ‘last known’ results.)

nd_service_registry.exceptions.ReadOnly

If readonly=True, any operation that would result in a ‘write’ will throw this exception. Most notably, a set() operation will fail with this exception if readonly=True.

API Documentation

Detailed implementation details and instructions are in the individual library files.