fetchers with function body

Fetcher functions exhibit different behavior based on whether they have a body or not. If a fetcher function does not have a body, it acts as a proxy, transmitting all provided arguments directly to the remote callback without any modification. On the other hand, if a fetcher function has a body, only the arguments returned from the function will be transmitted to the remote callback. This allows for additional intermediate logic to be executed before sending the arguments to the remote location.

Arguments can be returned as tuple or using special Args class.

class based approachdecorator based approach

calculator_service.py content:

import logging
from daffi import Global
from daffi.registry import Callback

logging.basicConfig(level=logging.INFO)


class CalculatorService(Callback):
    auto_init = True

    def calculate_sum(self, num1, num2):
        return num1 + num2

    def calculate_difference(self, num1, num2):
        return num1 - num2


if __name__ == '__main__':
    Global(init_controller=True, host="localhost", port=8888).join()

calculator_client.py content:

import logging
from daffi import Global
from daffi.registry import Fetcher, Args

logging.basicConfig(level=logging.INFO)


class CalculatorClient(Fetcher):

    def __post_init__(self):
        self.multiplier = 2

    def calculate_sum(self, num1, num2):
        """Return arguments as tuple"""
        num1 *= self.multiplier
        num2 *= self.multiplier
        return num1, num2


    def calculate_difference(self, num1, num2):
        """Return arguments as `Args` class"""
        num1 *= self.multiplier
        num2 *= self.multiplier
        return Args(num1=num1, num2=num2)


if __name__ == '__main__':
    g = Global(host="localhost", port=8888)

    calc_client = CalculatorClient()
    result = calc_client.calculate_sum(1, 2)
    print(result)

    result = calc_client.calculate_difference(50, 20)
    print(result)

    g.stop()

Execute in two separate terminals:

python3 calculator_service.py
python3 calculator_client.py

calculator_service.py content:

import logging
from daffi import Global
from daffi.decorators import callback

logging.basicConfig(level=logging.INFO)


@callback
def calculate_sum(num1, num2):
    return num1 + num2


@callback
def calculate_difference(num1, num2):
    return num1 - num2


if __name__ == '__main__':
    Global(init_controller=True, host="localhost", port=8888).join()

calculator_client.py content:

import logging
from daffi import Global
from daffi.decorators import fetcher
from daffi.registry import Args

logging.basicConfig(level=logging.INFO)

multiplier = 2


@fetcher
def calculate_sum(num1, num2):
    """Return arguments as tuple"""
    num1 *= multiplier
    num2 *= multiplier
    return num1, num2


@fetcher
def calculate_difference(num1, num2):
    """Return arguments as `Args` class"""
    num1 *= multiplier
    num2 *= multiplier
    return Args(num1=num1, num2=num2)


if __name__ == '__main__':
    g = Global(host="localhost", port=8888)

    result = calculate_sum(1, 2)
    print(result)

    result = calculate_difference(50, 20)
    print(result)

    g.stop()

Execute in two separate terminals:

python3 calculator_service.py
python3 calculator_client.py

Note

To use UNIX socket instead of TCP for communication, you should remove the host and port parameters from the initialization of the Global object, and optionally include the unix_sock_path parameter.