limitor 0.5.0

Rate limiting package

Rate Limiting Algorithms

This project adheres to Semantic Versioning

Algorithms

Algorithms	Sync	Async
Leaky Bucket	Yes	Yes
Token Bucket	Yes	Yes
Generic Cell Rate Algorithm	Yes	Yes
LLM-Token	Yes	Yes

[!NOTE]
Implementations will be single-threaded, blocking requests (or the equivalent) with burst capabilities. With asyncio, we use non-blocking cooperative multitasking, not preemptive multi-threading

Development

Setup uv-based virtual environment

# Install uv
# for a mac or linux
brew install uv
# OPTIONAL: or
curl -LsSf https://astral.sh/uv/install.sh | sh

# python version are automatically downloaded as needed or: uv python install 3.12
uv venv rate --python 3.12


# to activate the virtual environment
source .venv/bin/activate

# to deactivate the virtual environment
deactivate

Create lock file + requirements.txt

# after pyproject.toml is created
uv lock

uv export -o requirements.txt --quiet

Upgrade dependencies

# can use sync or lock
uv sync --upgrade

or 

# to upgrade a specific package
uv lock --upgrade-package requests

Usage

[!IMPORTANT] These are special use cases. The general use cases are in the examples/ folder

LLM Token-Based Rate Limiting

[!NOTE] This decorator assumes that the user will pass any necessary params. If you want to make these optional, see limitor/__init__.py

from functools import wraps
import random
import time
from typing import Callable

from limitor.base import SyncRateLimit
from limitor.configs import BucketConfig
from limitor.leaky_bucket.core import SyncLeakyBucket


def rate_limit(capacity: int = 10, seconds: float = 1, bucket_cls: type[SyncRateLimit] = SyncLeakyBucket) -> Callable:
    bucket = bucket_cls(BucketConfig(capacity=capacity, seconds=seconds))

    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            amount = kwargs.get("amount", 1)
            bucket.acquire(amount=amount)
            return func(*args, **kwargs)
        return wrapper

    return decorator

# limit of 100,000 tokens per second

@rate_limit(capacity=100_000, seconds=1)
def process_request(amount=1):
    print(f"This is a rate-limited function: {time.strftime('%X')} - {amount} tokens")

for _ in range(100):
    # generate random prompt tokens between 5,000 and 30,000 for 100 sample requests
    llm_prompt_tokens = random.randint(5_000, 30_000)
    try:
        process_request(amount=llm_prompt_tokens)
    except Exception as error:
        print(f"Rate limit exceeded: {error}")

With User-Specific Rate Limits + Cache

from functools import wraps
import time
from typing import Optional

from cachetools import LRUCache, TTLCache

from limitor.base import SyncRateLimit
from limitor.configs import BucketConfig
from limitor.leaky_bucket.core import (
    AsyncLeakyBucket,
    SyncLeakyBucket,
)


def _get_user_cache(max_users, ttl):
    if ttl is not None:
        return TTLCache(maxsize=max_users, ttl=ttl)
    return LRUCache(maxsize=max_users)

def rate_limit_per_user(capacity=10, seconds=1, max_users=1000, ttl=None, bucket_cls: type[SyncRateLimit] = SyncLeakyBucket):
    buckets = _get_user_cache(max_users, ttl)
    global_bucket = bucket_cls(BucketConfig(capacity=capacity, seconds=seconds))

    def decorator(func):
        # optional use_id. if not set, it will default to a regular global rate limiter
        # if user_id is not set, this means the max_users / ttl parameters will be ignored
        @wraps(func)
        def wrapper(*args, user_id=None, **kwargs):
            if user_id is None:
                bucket = global_bucket
            else:
                if user_id not in buckets:
                    buckets[user_id] = bucket_cls(BucketConfig(capacity=capacity, seconds=seconds))
                bucket = buckets[user_id]
            with bucket:
                return func(user_id, *args, **kwargs)

        return wrapper

    return decorator

@rate_limit_per_user(capacity=2, seconds=1, max_users=3, ttl=600)  # TTLCache: 10 min/user
def something_user(user_id):
    print(f"User {user_id} called at {time.strftime('%X')}")

for _ in range(20):
    try:
        x = 1 if _ % 2 == 0 else 0
        something_user(user_id=x)
    except Exception as error:
        print(f"Rate limit exceeded: {error}")