requests-ratelimiter 0.3.1

Rate-limiting for the requests library

Requests-Ratelimiter

This package is a simple wrapper around pyrate-limiter that adds convenient integration with the requests library.

Full project documentation can be found at requests-ratelimiter.readthedocs.io.

Features

• pyrate-limiter is a general-purpose rate limiting library that implements the leaky bucket algorithm, supports multiple rate limits, and has optional persistence with SQLite and Redis backends
• requests-ratelimiter adds some extra conveniences specific to sending HTTP requests with the requests library
• It can be used as a transport adapter, session, or session mixin for compatibility with other requests-based libraries
• Rate limits are tracked separately per host
• Different rate limits can optionally be applied to different hosts

Installation

pip install requests-ratelimiter

Usage

Sessions

Example with LimiterSession:

from requests import Session
from requests_ratelimiter import LimiterSession

# Apply a rate-limit (5 requests per second) to all requests
session = LimiterSession(per_second=5)

# Make rate-limited requests that stay within 5 requests per second
for _ in range(10):
    response = session.get('https://httpbin.org/get')
    print(response.json())

Adapters

Example with LimiterAdapter:

from requests import Session
from requests_ratelimiter import LimiterAdapter

session = Session()

# Apply a rate-limit (5 requests per second) to all requests
adapter = LimiterAdapter(per_second=5)
session.mount('http://', adapter)
session.mount('https://', adapter)

# Make rate-limited requests
for user_id in range(100):
    response = session.get(f'https://api.some_site.com/v1/users/{user_id}')
    print(response.json())

Per-Host Rate Limit Tracking

With either LimiterSession or LimiterAdapter, rate limits are tracked separately for each host. In other words, requests sent to one host will not count against the rate limit for any other hosts:

session = LimiterSession(per_second=5)

# Make requests for two different hosts
for _ in range(10):
    response = session.get(f'https://httpbin.org/get')
    print(response.json())
    session.get(f'https://httpbingo.org/get')
    print(response.json())

If you have a case where multiple hosts share the same rate limit, you can disable this behavior with the per_host option:

session = LimiterSession(per_second=5, per_host=False)

Per-Host Rate Limit Definitions

With LimiterAdapter, you can apply different rate limits to different hosts or URLs:

# Apply different rate limits (2/second and 100/minute) to a specific host
adapter_2 = LimiterAdapter(per_second=2, per_minute=100)
session.mount('https://api.some_site.com', adapter_2)

Behavior for matching requests is the same as other transport adapters: requests will use the adapter with the most specific (i.e., longest) URL prefix for a given request. For example:

session.mount('https://api.some_site.com/v1', adapter_3)
session.mount('https://api.some_site.com/v1/users', adapter_4)

# This request will use adapter_3
session.get('https://api.some_site.com/v1/')

# This request will use adapter_4
session.get('https://api.some_site.com/v1/users/1234')

Server-Side Rate Limit Behavior

Sometimes, server-side rate limiting may not behave exactly as documented (or may not be documented at all). Or you might encounter other scenarios where your client-side limit gets out of sync with the server-side limit. In most cases, a server will send a 429: Too Many Requests response for an exceeded rate limit.

When this happens, requests-ratelimiter will attempt to catch up to the server-side limit by adding an extra delay before the next request. This will use the smallest rate limit interval you've defined. For example, if you have a per-minute and per-hour limit, up to 1 minute of delay time will be added before the next request.

If a server sends a different status code to indicate an exceeded limit, you can set this via limit_statuses:

session = LimiterSession(per_second=5, limit_statuses=[429, 500])

Or if you would prefer to disable this behavior and handle it yourself:

session = LimiterSession(per_second=5, limit_statuses=[])

Backends

By default, rate limits are tracked in memory and are not persistent. You can optionally use either SQLite or Redis to persist rate limits across threads, processes, and/or application restarts. See pyrate-limiter docs for more details.

Compatibility

There are many other useful libraries out there that add features to requests, most commonly by extending or modifying requests.Session or requests.HTTPAdapter.

To use requests-ratelimiter with one of these libraries, you have a few different options:

1. If the library provides a custom Session class, mount a LimiterAdapter on it
2. Or use LimiterMixin to create a custom Session class with features from both libraries
3. If the library provides a custom Adapter class, use LimiterMixin to create a custom Adapter class with features from both libraries

Custom Session Example: Requests-Cache

For example, to combine with requests-cache, which also includes a separate mixin class:

from requests import Session
from requests_cache import CacheMixin, RedisCache
from requests_ratelimiter import LimiterMixin, RedisBucket


class CachedLimiterSession(CacheMixin, LimiterMixin, Session):
    """Session class with caching and rate-limiting behavior. Accepts arguments for both
    LimiterSession and CachedSession.
    """


# Optionally use Redis as both the bucket backend and the cache backend
session = CachedLimiterSession(
    per_second=5,
    bucket_class=RedisBucket,
    backend=RedisCache(),
)

This example has an extra benefit: cache hits won't count against your rate limit!