httpx-rate-limiter-transport 0.1.0

Async transport for httpx to implement various rate limiting (using a centralized redis as backend)

httpx-rate-limiter-transport

What is it?

This project provides an async transport for httpx to implement various rate limiting (using a centralized redis as backend).

Features

• Global semaphore to limit the number of concurrent requests to all hosts
• Optional second level of semaphore to limit the number of concurrent requests (you can provide your own logic)
  • for example: you can limit the number of concurrent requests by host, by HTTP method or only for some given hosts...
• TTL to avoid blocking the semaphore forever (in some special cases like computer crash or network issues at the very wrong moment)
• Can wrap another transport (if you already use one)

Roadmap

• Add a "request per minute" rate limiting

Installation

pip install httpx-rate-limiter-transport

Quickstart

import asyncio
import httpx
from httpx_rate_limiter_transport.backend.adapters.redis import (
    RedisRateLimiterBackendAdapter,
)
from httpx_rate_limiter_transport.transport import ConcurrencyRateLimiterTransport


def get_httpx_client() -> httpx.AsyncClient:
    transport = ConcurrencyRateLimiterTransport(
        global_concurrency=2,
        backend_adapter=RedisRateLimiterBackendAdapter(
            redis_url="redis://localhost:6379", ttl=300
        ),
    )
    return httpx.AsyncClient(transport=transport, timeout=300)


async def request(n: int):
    client = get_httpx_client()
    async with client:
        futures = [client.get("https://www.google.com/") for _ in range(n)]
        res = await asyncio.gather(*futures)
        for r in res:
            print(r.status_code)


if __name__ == "__main__":
    asyncio.run(request(10))

How-to

How to get a concurrency limit by host?

To get a "concurrency limit by host", you can provide 2 hooks to define a custom/second level of concurrency limit.

import httpx
from httpx_rate_limiter_transport.backend.adapters.redis import (
    RedisRateLimiterBackendAdapter,
)
from httpx_rate_limiter_transport.transport import ConcurrencyRateLimiterTransport


def get_httpx_client() -> httpx.AsyncClient:
    transport = ConcurrencyRateLimiterTransport(
        global_concurrency=100,  # global concurrency limit (for all requests)
        backend_adapter=RedisRateLimiterBackendAdapter(
            redis_url="redis://localhost:6379", ttl=300
        ),
        get_concurrency_hook=lambda request: 10,  # set a second level of concurrency limit of 10
        get_key_hook=lambda request: request.url.host,  # use the host as key for the second level of concurrency limit
    )
    return httpx.AsyncClient(transport=transport, timeout=300)

How to get a concurrency limit for only one given host?

To get a concurrency limit only for a given host, you can return None from your custom hooks to deactivate the concurrency control for this specific request.

import httpx
from httpx_rate_limiter_transport.backend.adapters.redis import (
    RedisRateLimiterBackendAdapter,
)
from httpx_rate_limiter_transport.transport import ConcurrencyRateLimiterTransport


def get_key_cb(request: httpx.Request) -> str | None:
    host = request.url.host
    if host == "www.google.com":
        # For google, no concurrency limit
        return None
    return host


def get_concurrency_cb(request: httpx.Request) -> int | None:
    # Let's return a constant concurrency limit of 10
    # (but of course, you can build your own logic here)
    return 10


def get_httpx_client() -> httpx.AsyncClient:
    transport = ConcurrencyRateLimiterTransport(
        global_concurrency=None,  # No global concurrency limit
        backend_adapter=RedisRateLimiterBackendAdapter(
            redis_url="redis://localhost:6379", ttl=300
        ),
        get_concurrency_hook=get_concurrency_cb,
        get_key_hook=get_key_cb,
    )
    return httpx.AsyncClient(transport=transport, timeout=300)

How to wrap another httpx transport?

If you already use a specific httpx transport, you can wrap it inside this one.

import httpx
from httpx_rate_limiter_transport.backend.adapters.redis import (
    RedisRateLimiterBackendAdapter,
)
from httpx_rate_limiter_transport.transport import ConcurrencyRateLimiterTransport


def get_httpx_client() -> httpx.AsyncClient:
    original_transport = httpx.AsyncHTTPTransport(retries=3)
    transport = ConcurrencyRateLimiterTransport(
        inner_transport=original_transport,  # let's wrap the original transport
        global_concurrency=10,
        backend_adapter=RedisRateLimiterBackendAdapter(
            redis_url="redis://localhost:6379", ttl=300
        ),
    )
    return httpx.AsyncClient(transport=transport, timeout=300)