RateLimiter

Simple Python module providing rate limiting.

Overview

This package provides the ratelimiter module, which ensures that an operation will not be executed more than a given number of times on a given period. This can prove useful when working with third parties APIs which require for example a maximum of 10 requests per second.

Usage

Decorator

from ratelimiter import RateLimiter

@RateLimiter(max_calls=10, period=1)
def do_something():
    pass

Context Manager

from ratelimiter import RateLimiter

rate_limiter = RateLimiter(max_calls=10, period=1)

for i in range(100):
    with rate_limiter:
        do_something()

Consume

For the case of limiting the rate of a specific unit metric rather than the execution of an operation as a whole, the ratelimiter module provides the consume attribute. This allows to limit our execution at a rate of bytes/s instead of block-operations/s. Note that bytes/s is just an example, similar to any other unit such as database capacitiy per second etc. The consume attribute can be modified during execution to account for varying unit sizes.

from ratelimiter import RateLimiter

rate_limiter = RateLimiter(max_calls=10, period=1, consume=2)
# Time duration of the following operation will be doubled
for i in range(100):
    with rate_limiter:
        do_something()

from ratelimiter import RateLimiter

rate_limiter = RateLimiter(max_calls=1024, period=1)
# Stream of data
packets = [ bytearray(512), bytearray(2048), bytearray(1024), bytearray(512) ]

for packet in packets:
    with rate_limiter:
        send(packet)
        # Consume the length of the packet
        rate_limiter.consume = packet.length

Callback

The callback is called in its own thread, so your callback may use sleep without delaying the rate limiter.

import time

from ratelimiter import RateLimiter

def limited(until):
    duration = int(round(until - time.time()))
    print('Rate limited, sleeping for {:d} seconds'.format(duration))

rate_limiter = RateLimiter(max_calls=2, period=3, callback=limited)

for i in range(3):
    with rate_limiter:
        print('Iteration', i)

Output:

Iteration 0
Iteration 1
Rate limited, sleeping for 3 seconds
Iteration 2

asyncio

The RateLimiter object can be used in an async with statement on Python 3.5+. Note that the callback must be a coroutine in this context. The coroutine callback is not called in a separate thread.

import asyncio
import time

from ratelimiter import RateLimiter

async def limited(until):
    duration = int(round(until - time.time()))
    print('Rate limited, sleeping for {:d} seconds'.format(duration))

async def coro():
    rate_limiter = RateLimiter(max_calls=2, period=3, callback=limited)
    for i in range(3):
        async with rate_limiter:
            print('Iteration', i)

loop = asyncio.get_event_loop()
loop.run_until_complete(coro())

License

Original work Copyright 2013 Arnaud Porterie

Modified work Copyright 2016 Frazer McLean

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.