aio

aioredlock

🔒 The asyncio implemetation of Redis distributed locks

Showing:

Popularity

Downloads/wk

0

GitHub Stars

200

Maintenance

Last Commit

3mos ago

Contributors

18

Package

Dependencies

12

License

MIT

Categories

Readme

aioredlock

.. image:: https://github.com/joanvila/aioredlock/workflows/Tests/badge.svg :target: https://travis-ci.org/joanvila/aioredlock

.. image:: https://codecov.io/gh/joanvila/aioredlock/branch/master/graph/badge.svg :target: https://codecov.io/gh/joanvila/aioredlock

.. image:: https://badge.fury.io/py/aioredlock.svg :target: https://pypi.python.org/pypi/aioredlock

The asyncio redlock_ algorithm implementation.

Redlock and asyncio

The redlock algorithm is a distributed lock implementation for Redis. There are many implementations of it in several languages. In this case, this is the asyncio compatible implementation for python 3.5+.

Usage

.. code-block:: python

from aioredlock import Aioredlock, LockError, Sentinel

Define a list of connections to your Redis instances:

redis_instances = [ ('localhost', 6379), {'host': 'localhost', 'port': 6379, 'db': 1}, 'redis://localhost:6379/2', Sentinel(('localhost', 26379), master='leader', db=3), Sentinel('redis://localhost:26379/4?master=leader&encoding=utf-8'), Sentinel('rediss://:password@localhost:26379/5?master=leader&encoding=utf-8&ssl_cert_reqs=CERT_NONE'), ]

Create a lock manager:

lock_manager = Aioredlock(redis_instances)

Check wether a resourece acquired by any other redlock instance:

assert not await lock_manager.is_locked("resource_name")

Try to acquire the lock:

try: lock = await lock_manager.lock("resource_name", lock_timeout=10) except LockError: print('Lock not acquired') raise

Now the lock is acquired:

assert lock.valid assert await lock_manager.is_locked("resource_name")

Extend lifetime of the lock:

await lock_manager.extend(lock, lock_timeout=10)

Raises LockError if the lock manager can not extend the lock lifetime

on more then half of the Redis instances.

Release the lock:

await lock_manager.unlock(lock)

Raises LockError if the lock manager can not release the lock

on more then half of redis instances.

The released lock become invalid:

assert not lock.valid assert not await lock_manager.is_locked("resource_name")

Or you can use the lock as async context manager:

try: async with await lock_manager.lock("resource_name") as lock: assert lock.valid is True

      # Do your stuff having the lock
      await lock.extend()  # alias for lock_manager.extend(lock)
      # Do more stuff having the lock
  assert lock.valid is False # lock will be released by context manager

except LockError: print('Lock not acquired') raise

Clear the connections with Redis:

await lock_manager.destroy()

How it works

The Aioredlock constructor accepts the following optional parameters:

  • redis_connections: A list of connections (dictionary of host and port and kwargs for aioredis.create_redis_pool(), or tuple (host, port), or string Redis URI) where the Redis instances are running. The default value is [{'host': 'localhost', 'port': 6379}].
  • retry_count: An integer representing number of maximum allowed retries to acquire the lock. The default value is 3 times.
  • retry_delay_min and retry_delay_max: Float values representing waiting time (in seconds) before the next retry attempt. The default values are 0.1 and 0.3, respectively.

In order to acquire the lock, the lock function should be called. If the lock operation is successful, lock.valid will be true, if the lock is not acquired then the LockError will be raised.

From that moment, the lock is valid until the unlock function is called or when the lock_timeout is reached.

Call the extend function to reset lifetime of the lock to lock_timeout interval.

Use the is_locked function to check if the resource is locked by other redlock instance.

In order to clear all the connections with Redis, the lock_manager destroy method can be called.

To-do

.. _redlock: https://redis.io/topics/distlock .. _Redis: https://redis.io .. _asyncio: https://docs.python.org/3/library/asyncio.html

Rate & Review

Great Documentation0
Easy to Use0
Performant0
Highly Customizable0
Bleeding Edge0
Responsive Maintainers0
Poor Documentation0
Hard to Use0
Slow0
Buggy0
Abandoned0
Unwelcoming Community0
100