remotipy

Remote RPC over HTTP for python (v0.1.2) - With remote exceptions support

Setup:

pip install remotipy

Step 1: Define the DTO (Client & Server)

In module data.dto (example) describe the transfer objects (DTO):

@serializable
class UserInfo(object):
    def __init__(self, params={}):
        self.first_name = params.get('first_name')
        self.last_name = params.get('last_name')
        self.email = params.get('email')
        
@serializable
class Result(object):
    def __init__(self, msg = None):
        self.message = msg

Note: share this file both on the client and the server

Step 2: Define empty stub client side (Client)

Use the decorator @remote to specify the rest endpoint and the module containing the models:

from data import models

@remote("http://localhost:5000/method_dispatcher", models)
class RemoteController(object):

    def my_remote_method(self, user):
        pass

Note: @remote supports custom HTTP headers using this format:

@remote("http://localhost:5000/method_dispatcher", data.models, headers={
            'X-Authentication-token': TokenGenerator.generate({'key': 123456789})
          })

Step 3: Define the remote logic (Server)

Implement the actual logic

class Controller(object):

    def my_remote_method(self, user):
        # all your logic here
        return Result(user.email + ' DONE!')

Step 4: Define the rest endpoint (Server)

You can use any python rest server to dispatch the body of the request to the invoked method. In this example we are using the Flask format.

@app.route('/method_dispatcher', methods=['POST'])
def query():
    # check http header, cookies, etc
    # dispatch format: controller_class, models_module, raw_body 
    result = rpc.dispatch(Controller, models, request.get_data())
    return response(result)

Note: the function response is required to serialize back the response

Step 5: Enjoy

On the client now you can call:

result = Controller().my_remote_method(user)

---

More info:

Just check the tests module for different test cases.

Known limitations:

The constructor def __init__(self, [ params={}, ... ] ) of the serializable objects (step 1) MUST support the empty call.

FAQ:

1. How can I handle a remote exception? Remote exception are raised on the client side with type remotipy.rpc.RemoteException and you have access to the original message (.message) and the original class name (.cls)
2. I get MethodNotFound: <my_remote_method>. Why? Check the interface on the client side and the implementation on the server side have the same methods signatures: steps 2/3. (You could even copy same file on the client because the methods body is ignored)
3. I'm using App Engine and I get TypeError('expected httplib.Message). Why? This is a known issue of urllib3&Python 2.7, to fix this go in <lib_dir_>/urllib3/util/response.py and remove from line 47 to 49.