2.6. Context

Services can require each other’s data. In this case, you should use Context.

Context is a repository associated with the running entrypoint.

Context-object will be created when entrypoint starts and linked to the running event loop.

Cross-dependent services might await or set each other’s data via the context.

For service instances self.context is available since entrypoint started. In other cases get_context() function returns current context.

import asyncio
from random import random, randint

from aiomisc import entrypoint, get_context, Service


class LoggingService(Service):
    async def start(self):
        context = get_context()

        wait_time = await context['wait_time']

        print('Wait time is', wait_time)
        self.start_event.set()

        while True:
            print('Hello from service', self.name)
            await asyncio.sleep(wait_time)


class RemoteConfiguration(Service):
    async def start(self):
        # querying from remote server
        await asyncio.sleep(random())

        self.context['wait_time'] = randint(1, 5)


services = (
    LoggingService(name='#1'),
    LoggingService(name='#2'),
    LoggingService(name='#3'),
    RemoteConfiguration()
)

with entrypoint(*services) as loop:
    pass

Note

It’s not a silver bullet. In base case services can be configured by passing kwargs to the service __init__ method.