:lock: The asyncio implemetation of Redis distributed locks
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The asyncio redlock_ algorithm implementation.
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+.
.. code-block:: python
from aioredlock import Aioredlock, LockError, Sentinel
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'), ]
lock_manager = Aioredlock(redis_instances)
assert not await lock_manager.is_locked("resource_name")
try: lock = await lock_manager.lock("resource_name", lock_timeout=10) except LockError: print('Lock not acquired') raise
assert lock.valid assert await lock_manager.is_locked("resource_name")
await lock_manager.extend(lock, lock_timeout=10)
await lock_manager.unlock(lock)
assert not lock.valid assert not await lock_manager.is_locked("resource_name")
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
await lock_manager.destroy()
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.
.. _redlock: https://redis.io/topics/distlock .. _Redis: https://redis.io .. _asyncio: https://docs.python.org/3/library/asyncio.html