Dispatching

Dispatching in tinyrpc is very similiar to url-routing in web frameworks. Functions are registered with a specific name and made public, i.e. callable, to remote clients.

Examples

Exposing a few functions:

from tinyrpc.dispatch import RPCDispatcher

dispatch = RPCDispatcher()

@dispatch.public
def foo():
    # ...

@dispatch.public
def bar(arg):
    # ...

# later on, assuming we know we want to call foo(*args, **kwargs):

f = dispatch.get_method('foo')
f(*args, **kwargs)

Using prefixes and instance registration:

from tinyrpc.dispatch import public

class SomeWebsite(object):
    def __init__(self, ...):
        # note: this method will not be exposed

    def secret(self):
        # another unexposed method

    @public
    def get_user_info(self, user):
        # ...

    # using a different name
    @public('get_user_comment')
    def get_comment(self, comment_id):
        # ...

The code above declares an RPC interface for SomeWebsite objects, consisting of two visible methods: get_user_info(user) and get_user_comment(commend_id).

These can be used with a dispatcher now:

def hello():
    # ...

website1 = SomeWebsite(...)
website2 = SomeWebsite(...)

from tinyrpc.dispatch import RPCDispatcher

dispatcher = RPCDispatcher()

# directly register version method
@dispatcher.public
def version():
    # ...

# add earlier defined method
dispatcher.add_method(hello)

# register the two website instances
dispatcher.register_instance(website1, 'sitea.')
dispatcher.register_instance(website2, 'siteb.')

In the example above, the RPCDispatcher now knows a total of six registered methods: version, hello, sitea.get_user_info, sitea.get_user_comment, siteb.get_user_info, siteb.get_user_comment.

Automatic dispatching

When writing a server application, a higher level dispatching method is available with dispatch():

from tinyrpc.dispatch import RPCDispatcher

dispatcher = RPCDispatcher()

# register methods like in the examples above
# ...
# now assumes that a valid RPCRequest has been obtained, as `request`

response = dispatcher.dispatch(request)

# response can be directly processed back to the client, all Exceptions have
# been handled already

API reference

class tinyrpc.dispatch.RPCDispatcher

Stores name-to-method mappings.

add_method(f, name=None)

Add a method to the dispatcher.

Parameters:
  • f – Callable to be added.
  • name – Name to register it with. If None, f.__name__ will be used.
add_subdispatch(dispatcher, prefix='')

Adds a subdispatcher, possibly in its own namespace.

Parameters:
  • dispatcher – The dispatcher to add as a subdispatcher.
  • prefix – A prefix. All of the new subdispatchers methods will be available as prefix + their original name.
dispatch(request)

Fully handle request.

The dispatch method determines which method to call, calls it and returns a response containing a result.

No exceptions will be thrown, rather, every exception will be turned into a response using error_respond().

If a method isn’t found, a MethodNotFoundError response will be returned. If any error occurs outside of the requested method, a ServerError without any error information will be returend.

If the method is found and called but throws an exception, the exception thrown is used as a response instead. This is the only case in which information from the exception is possibly propagated back to the client, as the exception is part of the requested method.

RPCBatchRequest instances are handled by handling all its children in order and collecting the results, then returning an RPCBatchResponse with the results.

Parameters:request – An RPCRequest().
Returns:An RPCResponse().
get_method(name)

Retrieve a previously registered method.

Checks if a method matching name has been registered.

If get_method() cannot find a method, every subdispatcher with a prefix matching the method name is checked as well.

If a method isn’t found, a KeyError is thrown.

Parameters:
  • name – Callable to find.
  • return – The callable.
public(name=None)

Convenient decorator.

Allows easy registering of functions to this dispatcher. Example:

dispatch = RPCDispatcher()

@dispatch.public
def foo(bar):
    # ...

class Baz(object):
    def not_exposed(self):
        # ...

    @dispatch.public(name='do_something')
    def visible_method(arg1)
        # ...
Parameters:name – Name to register callable with
register_instance(obj, prefix='')

Create new subdispatcher and register all public object methods on it.

To be used in conjunction with the tinyrpc.dispatch.public() decorator (not tinyrpc.dispatch.RPCDispatcher.public()).

Parameters:
  • obj – The object whose public methods should be made available.
  • prefix – A prefix for the new subdispatcher.

Classes can be made to support an RPC interface without coupling it to a dispatcher using a decorator:

tinyrpc.dispatch.public(name=None)

Set RPC name on function.

This function decorator will set the _rpc_public_name attribute on a function, causing it to be picked up if an instance of its parent class is registered using register_instance().

@public is a shortcut for @public().

Parameters:name – The name to register the function with.