nameko with dynamic call of service

shell

>>> n.rpc.service.for_who('service_a', 'foobar')
'i'm in read_data of <class 'test.ServiceA'> with payload foobar
error handling worker <WorkerContext [service.for_who] at 0x7f714960c5c0>: 'EventDispatcher' object is not callable
Traceback (most recent call last):
  File "/home/foxmask/DjangoVirtualEnv/namekotst/lib/python3.6/site-packages/nameko/containers.py", line 388, in _run_worker
    result = method(*worker_ctx.args, **worker_ctx.kwargs)
  File "./test.py", line 28, in for_who
    t.read_data(payload)
  File "./test.py", line 40, in read_data
    self.dispatch("save_data", payload)
TypeError: 'EventDispatcher' object is not callable
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/foxmask/DjangoVirtualEnv/namekotst/lib/python3.6/site-packages/nameko/rpc.py", line 374, in __call__
    return reply.result()
  File "/home/foxmask/DjangoVirtualEnv/namekotst/lib/python3.6/site-packages/nameko/rpc.py", line 332, in result
    raise deserialize(error)
nameko.exceptions.RemoteError: TypeError 'EventDispatcher' object is not callable

test.py

from nameko.events import EventDispatcher, event_handler
from nameko.rpc import rpc


class ServiceFactory:

    def factory(service_name):
        if service_name == "service_a":
            return ServiceA()
        if service_name == "service_b":
            return ServiceB()
        if service_name == "service_c":
            return ServiceC()
        assert 0, "Bad service_name : " + service_name

    factory = staticmethod(factory)


class Service(ServiceFactory):

    name = "service"

    dispatch = EventDispatcher()

    @rpc
    def for_who(self, service_name, payload):
        t = ServiceFactory.factory(service_name)
        t.read_data(payload)


class ServiceA:
    """ Event dispatching service. """
    name = "service_a"

    dispatch = EventDispatcher()

    @rpc
    def read_data(self, payload):
        print("'i'm in read_data of {} with payload {}".format(self.__class__, payload))
        self.dispatch("save_data", payload)

    @event_handler("service", "save_data")
    def handle_event(self, payload):
        print("service A received:", payload)


class ServiceB:
    """ Event listening service. """
    name = "service_b"

    @rpc
    def read_data(self, payload):
        self.dispatch("save_data", payload)

    @event_handler("service", "save_data")
    def handle_event(self, payload):
        print("service b received:", payload)

class ServiceC:
    """ Event dispatching service. """
    name = "service_c"

    dispatch = EventDispatcher()

    @rpc
    def read_data(self, payload):
        self.dispatch("save_data", payload)

    @event_handler("service", "save_data")
    def handle_event(self, payload):
        print("service C received:", payload)

Nameko uses Python classes to describe services. Instantiating one is not sufficient to make it run as a service, so the object you're returning from your ServiceFactory are not services.

You could achieve your desired outcome by maintaining multiple RPC proxies:

class Service(ServiceFactory):

    name = "service"

    service_a_rpc = RpcProxy('a')
    service_b_rpc = RpcProxy('b')
    service_c_rpc = RpcProxy('c')

    @rpc
    def for_who(self, service_name, payload):
        proxy = getattr(self, f'{service_name}_rpc')
        proxy(payload)

Note that this does not dynamically start the downstream services.