pie-lock 0.1.7

A library for python distributed lock, optimistic lock and limiter

Pie-lock

All lock module using redis for control.

Installation

With Pypi:

pip install pie-lock

With Github:

pip install git+https://github.com/bacsiTuan/pielock.git

Usage Distributed Lock

key = "test1"
success, msg = redis_lock.acquire(key)
print(msg)
if not success:
    print(msg)
redis_lock.release(key)

Usage Optimistic Lock

def test_optimistic_lock(self):
    is_locked1, msg = redis_lock.acquire("key1")
    if not is_locked1:
        print(msg)
    is_locked2, msg = redis_lock.acquire("key1")
    if not is_locked2:
        print(msg)
    is_locked3, msg = redis_lock.acquire("key1")
    if not is_locked3:
        print(msg)
    release, msg = redis_lock.release("key1")
    if not release:
        print(msg)
    is_locked4, msg = redis_lock.acquire("key1")
    if not is_locked4:
        print(msg)

Configuration

Redis configuration

from pie_lock.backends import DistributedLock

redis_lock = DistributedLock(
    expires=5,
    timeout=5,
    retry_after=1, # seconds between retries
    tries=32,  # max number of tries
)
redis_lock.get_client(
    host="localhost",
    port=19821,
    password="passsword",
    username="default"
)

Note: all fields after the scheme are optional, and will default to localhost on port 6379, using database 0.

DEFAULT_TIMEOUT (default: 60)

If another client has already obtained the lock, sleep for a maximum of this many seconds before giving up. A value of 0 means no wait (give up right away).

The default timeout can be overridden when instantiating the lock.

Limiter

Based on sliding window algorithm

from pie_lock.backends import Limiter, TimeUnit

redis = Limiter(
    host="localhost",
    port=19821,
    password="passsword",
    username="default",
    socket_timeout=2,
)

for i in range(6):
    allow, msg = redis.allow(redis_key="mylist", per=TimeUnit.SECOND, count=2)
    if not allow:
        print(msg)
time.sleep(1)
allow, msg = redis.allow(redis_key="mylist", per=TimeUnit.SECOND, count=2)
if not allow:
    print(msg)

We consider any existing lock older than this many seconds to be invalid
in order to detect crashed clients. This value must be higher than it
takes the critical section to execute.

The default expires can be overridden when instantiating the lock.