Does LRU caching prevent sentry from creating multiple instances?

Question

I am using sentry to monitor my application. The initialization is done like thus:

from functools import lru_cache
import sentry_sdk

@lru_cache
def start_sentry():
    sentry_instance = sentry_sdk.init(DSN)
    return sentry_instance

Now, if i were to execute start_sentry multiple times, the multiple sentry_instances created are actually all pointing to the same object in memory. Without using the lru_cache decorator, new sentry instances are crated in memory. So my question is: is using lru caching doing what I am expecting, that is - will it only initialize sentry once even though i attempt to do it multiple times?

i am on python3.6.7 sentry-sdk==0.10.2

score 1 · Accepted Answer · answered Jul 14 '23 at 01:57

It will work like that provided it's called within the same process.

That's a big if. Depending on your web application, workers might be pre-forked, and in this case the cache doesn't work across processes.

A minimal example to reproduce that is:

from functools import lru_cache
from multiprocessing import Process


@lru_cache
def start_sentry():
    print("starting sentry")
    ...
    return


if __name__ == "__main__":
    proc1 = Process(target=start_sentry)
    proc1.start()
    proc1.join()
    proc2 = Process(target=start_sentry)
    proc2.start()
    proc2.join()

You will see "starting sentry" printed twice with this code, because each process got its own cache and they have no way of talking to eachother.

Does LRU caching prevent sentry from creating multiple instances?

1 Answers1