Understanding aiohttp.ClientSession

keep_alive.py

from time import time
import asyncio

import aiohttp
from aiohttp import web


async def web_handler(request):
    n = int(request.GET.get('n', 0))
    return web.Response(text=str(n+1))


async def init_app(loop):
    app = web.Application(loop=loop)
    app.router.add_route('GET', '/', web_handler)
    return app


class TaskPool:
    def __init__(self, tasks, max_threads=10, loop=None):
        self.semaphore = asyncio.Semaphore(max_threads)
        self.loop = loop or asyncio.get_event_loop()
        self.coros = [self.add_task(task) for task in tasks]

    def run(self):
        self.loop.run_until_complete(asyncio.wait(self.coros))

    async def add_task(self, task):
        with (await self.semaphore):
            await self.process_task(task)

    async def process_task(self, task):
        raise NotImplementedError


class Client(TaskPool):
    session = aiohttp

    async def process_task(self, n):
        async with self.session.get('http://127.0.0.1:8000',
                                    params={'n': n}) as r:
            result = int(await r.text())
            assert result == n + 1


class SessionClient(Client):
    session = aiohttp.ClientSession()


def bench(client_cls, num_requests, num_threads):
    client = client_cls(range(num_requests), num_threads)
    started = time()
    client.run()
    took = time() - started
    print('{:15} made {} requests with {:2} threads in {} seconds'.format(
        client_cls.__name__, num_requests, num_threads, took))


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    app = loop.run_until_complete(init_app(loop))
    handler = app.make_handler()
    srv = loop.run_until_complete(
        loop.create_server(handler, '127.0.0.1', 8000))
    print('Serving at http://{}:{}/'.format(*srv.sockets[0].getsockname()))

    bench(Client, 100, 1)
    bench(SessionClient, 100, 1)
    bench(Client, 100, 10)
    bench(SessionClient, 100, 10)

    SessionClient.session.close()
    loop.run_until_complete(handler.finish_connections(1.0))
    srv.close()
    loop.run_until_complete(srv.wait_closed())
    loop.run_until_complete(app.finish())
    loop.close()

result.txt

Client          made 100 requests with  1 threads in 0.3546574115753174 seconds
SessionClient   made 100 requests with  1 threads in 3.984743595123291 seconds
Client          made 100 requests with 10 threads in 0.32209348678588867 seconds
SessionClient   made 100 requests with 10 threads in 0.42948365211486816 seconds