aiohttp: set maximum number of requests per second

Question

How can I set maximum number of requests per second (limit them) in client side using aiohttp?

Answer 1

You could set a delay per request or group the URLs in batches and throttle the batches to meet desired frequency.

1. Delay per request

Force the script to wait in between requests using asyncio.sleep

import asyncio
import aiohttp

delay_per_request = 0.5
urls = [
   # put some URLs here...
]

async def app():
    tasks = []
    for url in urls:
        tasks.append(asyncio.ensure_future(make_request(url)))
        await asyncio.sleep(delay_per_request)

    results = await asyncio.gather(*tasks)
    return results

async def make_request(url):
    print('$$$ making request')
    async with aiohttp.ClientSession() as sess:
        async with sess.get(url) as resp:
            status = resp.status
            text = await resp.text()
            print('### got page data')
            return url, status, text

This can be run with e.g. results = asyncio.run(app()).

2. Batch throttle

Using make_request from above, you can request and throttle batches of URLs like this:

import asyncio
import aiohttp
import time

max_requests_per_second = 0.5
urls = [[
   # put a few URLs here...
],[
   # put a few more URLs here...
]]

async def app():
    results = []
    for i, batch in enumerate(urls):
        t_0 = time.time()
        print(f'batch {i}')
        tasks = [asyncio.ensure_future(make_request(url)) for url in batch]
        for t in tasks:
            d = await t
            results.append(d)
        t_1 = time.time()

        # Throttle requests
        batch_time = (t_1 - t_0)
        batch_size = len(batch)
        wait_time = (batch_size / max_requests_per_second) - batch_time
        if wait_time > 0:
            print(f'Too fast! Waiting {wait_time} seconds')
            time.sleep(wait_time)

    return results

Again, this can be run with asyncio.run(app()).