Lock - Getting Started with Locks in Py-Cachify¶

Starting slow¶

Let's write the following code:

import asyncio

from py_cachify import init_cachify, lock


# here we initializing a py-cachify to use an in-memory cache, as usual
init_cachify()


async def main() -> None:

    # this is a sync lock
    with lock(key='cool-sync-lock'):
        print('this code is locked')

    # and this is an async lock
    async with lock(key='cool-async-lock'):
        print('this code is locked, but using async cache')


if __name__ == '__main__':
    asyncio.run(main())

If we run the example:

# Run our examplepython main.py# The output will bethis code is locked
this code is locked, but using async cache

As you can see, we just had both of our prints printed out without any exceptions.

Notice how we utilized both sync and async context managers from a single lock object, by doing this py-cachify allows you to use the lock in any environment your application might work in (sync or async), without splitting those into for example async_lock and sync_lock.

From now on we will do everything in async, but you can also follow the tutorial writing the same sync code :)

Let's break it¶

Now, we'll adjust our previous example:

import asyncio

from py_cachify import init_cachify, lock


# here we initializing a py-cachify to use an in-memory cache, as usual
init_cachify()


async def main() -> None:

    # and this is an async lock
    async with lock(key='cool-async-lock'):
        print('this code is locked and will be executed')

        async with lock(key='cool-async-lock'):
            print('we are attempting to acquire a new lock with the same key and will not make it to this print')


if __name__ == '__main__':
    asyncio.run(main())

After running this piece:

python main.py# The output will bepoetry run python main.py
this code is locked and will be executed
cool-async-lock is already locked! # this is a .warning from log
# traceback of an errorTraceback (most recent call last):
...
File "/py_cachify/backend/lock.py", line 199, in _raise_if_cached
raise CachifyLockError(msg)
py_cachify.backend.exceptions.CachifyLockError: cool-async-lock is already locked!

And as expected, at the line where we are trying to acquire a lock with the same name - we get an error that this key is already locked.

This was a showcase of the very basic piece of locks (or mutexes) and everything else everywhere is built on top of this basic concept.

What's next¶

We will see what parameters does lock object has and what cases can we cover with the help of those.