wampy 0.9.4

WAMP RPC and Pub/Sub for python apps and microservices

wampy

WAMP RPC and Pub/Sub for your Python apps and microservices

This is a Python implementation of WAMP not requiring Twisted or asyncio, enabling use within classic blocking Python applications. It is a light-weight alternative to autobahn.

With wampy you can quickly and easily create your own WAMP clients, whether this is in a web app, a microservice, a script or just in a Python shell.

wampy tries to provide an intuitive API for your WAMP messaging.

See ReadTheDocs for more detailed documentation.

Quickstart: wampy from the command line

Before any messaging can happen you do need that Router I mentioned. Messages are then routed between Clients over an administrative domain on the Router called a Realm.

For the quickest of starts I suggest that you use Crossbar.io and start it up on the default host and port, and with the default realm and roles. See the Crossbar.io docs for the instructions on this or alternatively run with wampy’s testing setup.

$ pip install --editable .[dev]

$ crossbar start --config ./wampy/testing/configs/crossbar.config.ipv4.json

By default a wampy client connects to localhost on port 8080, but this is of course configurable, and is done so on client initialisation.

wampy RPC

Now open your preferred text editor and we’ll write a few lines of Python constructing a simple WAMP service that takes a decimal number and returns the binary representation of it - wowzers!

In [1]: from wampy.peers.clients import Client

In [2]: from wampy.roles import callee

In [3]: class BinaryNumberService(Client):

            @callee
            def get_binary_number(self, number):
                return bin(number)

Save this module somewhere on your Python path and we’ll use a wampy command line interface tool to start the service.

$ wampy run path.to.your.module.including.module_name:BinaryNumberService

For example, running one of the wampy example applications.

$ wampy run docs.examples.services:DateService --config './path/to/crossbar.config.json'

Okay, no need to write any code: execute this:

$ wampy run docs.examples.services:BinaryNumberService --config './wampy/testing/configs/crossbar.config.ipv4.json'

Now, open a Python console in a new terminal, allowing the BinaryNumberService to run uninterupted in your original terminal (but once you’re done with it Ctrl-C is required).

In [1]: from wampy.peers.clients import Client

In [2]: from wampy.peers.routers import Crossbar

In [3]: with Client(router=Crossbar()) as client:
            result = client.rpc.get_binary_number(number=100)

In [4]: result
Out[4]: u'0b1100100'

wampy RPC for Crossbar.io

The RPC pattern above was inspired by the nameko project, but this pattern may not feel intuitive for those familiar with Crossbar.io, the primary Router used by wampy.

For this reason there also exists the CallProxy object which implements the call API by more loosely wrapping wampy’s Call Message. In this pattern, applications and their endpoints are identified by dot delimented strings rather than a single API name, e.g.

"com.example.endpoint"

Just like the rpc API, the call API is directly available on every wampy client. Lets look at the two examples side by side.

>>> client.rpc.get_foo_bar(eggs, foo=bar, spam=ham)
>>> client.call("get_foo_bar", eggs, foo=bar, spam=ham)

Noted these are very similar and achieve the same, but the intention here is for the call API to behave more like a classic Crossbar.io application and the rpc to be used in nameko_wamp.

The call API however does allow calls of the form…

>>> client.call("com.myapp.foo.bar", eggs, foo=bar, spam=ham)

…which you will not be able to do with the rpc API.

Publishing and Subscribing is equally as simple

To demonstrate, first of all you need a Subscriber. You can either create one yourself in a Python module (as a subclass of a wampy Client) or use the example Client already for you in docs.examples.services.

Here we use the said example service, but all a Subscriber is is a wampy Client with a method decorated by subscribe. Take a look and see for yourself in the examples.

Let’s start up that example service.

$ wampy run docs.examples.services:SubscribingService --config './wampy/testing/configs/crossbar.config.ipv4.json'

Now we have a service running that subscribes to the topic “foo”.

In another terminal, with a wampy virtualenv, you can create a Publisher - which is no different to any other wampy Client.

In [1]: from wampy.peers.clients import Client

In [2]: from wampy.peers.routers import Crossbar

In [3]: with Client(router=Crossbar()) as client:
            result = client.publish(topic="foo", message="spam")

Hopefully you’ll see any message you send printed to the screen where the example service is running. You’ll also see the meta data that wampy chooses to send.

See ReadTheDocs for more detailed documentation.

Running the tests

$ pip install --editable .[dev]
$ py.test ./test -v

Build the docs

$ pip install -r rtd_requirements.txt
$ sphinx-build -E -b html ./docs/ ./docs/_build/

If you like this project, then Thank You, and you’re welcome to get involved.