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limits

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limits is a python library to perform rate limiting with commonly used storage backends (Redis, Memcached & MongoDB).

Supported Strategies

Fixed Window <https://limits.readthedocs.io/en/latest/strategies.html#fixed-window>_ This strategy resets at a fixed interval (start of minute, hour, day etc). For example, given a rate limit of 10/minute the strategy will:

• Allow 10 requests between 00:01:00 and 00:02:00
• Allow 10 requests at 00:00:59 and 10 more requests at 00:01:00

Fixed Window (Elastic) <https://limits.readthedocs.io/en/latest/strategies.html#fixed-window-with-elastic-expiry>_ Identical to Fixed window, except every breach of rate limit results in an extension to the time out. For example a rate limit of 1/minute hit twice within a minute will result in a lock-out for two minutes.

Moving Window <https://limits.readthedocs.io/en/latest/strategies.html#moving-window>_ Sliding window strategy enforces a rate limit of N/(m time units) on the last m time units at the second granularity.

For example, with a rate limit of 10/minute:

• Allow 9 requests that arrive at 00:00:59
• Allow another request that arrives at 00:01:00
• Reject the request that arrives at 00:01:01

Storage backends

• Redis <https://limits.readthedocs.io/en/latest/storage.html#redis>_
• Memcached <https://limits.readthedocs.io/en/latest/storage.html#memcached>_
• In-Memory <https://limits.readthedocs.io/en/latest/storage.html#in-memory>_
• MongoDB <https://limits.readthedocs.io/en/latest/storage.html#mongodb>_

Dive right in

Initialize the storage backend

.. code-block:: python

from limits import storage memory_storage = storage.MemoryStorage()

or memcached

memcached_storage = storage.MemcachedStorage("memcached://localhost:11211")

or redis

redis_storage = storage.RedisStorage("redis://localhost:6379")

or leave it to fate

some_storage = storage.storage.from_string(fate)

Initialize a rate limiter with the Moving Window Strategy

.. code-block:: python

from limits import strategies moving_window = strategies.MovingWindowRateLimiter(memory_storage)

Initialize a rate limit

.. code-block:: python

from limits import parse
one_per_minute = parse("1/minute")

Initialize a rate limit explicitly

.. code-block:: python

from limits import RateLimitItemPerSecond
one_per_second = RateLimitItemPerSecond(1, 1)

Test the limits

.. code-block:: python

assert True == moving_window.hit(one_per_minute, "test_namespace", "foo")
assert False == moving_window.hit(one_per_minute, "test_namespace", "foo")
assert True == moving_window.hit(one_per_minute, "test_namespace", "bar")

assert True == moving_window.hit(one_per_second, "test_namespace", "foo")
assert False == moving_window.hit(one_per_second, "test_namespace", "foo")
time.sleep(1)
assert True == moving_window.hit(one_per_second, "test_namespace", "foo")

Check specific limits without hitting them

.. code-block:: python

assert True == moving_window.hit(one_per_second, "test_namespace", "foo")
while not moving_window.test(one_per_second, "test_namespace", "foo"):
    time.sleep(0.01)
assert True == moving_window.hit(one_per_second, "test_namespace", "foo")

Links

• Documentation <http://limits.readthedocs.org/en/latest>_
• Changelog <http://limits.readthedocs.org/en/stable/changelog.html>_