Explore: Task scheduling API

[casperisfine]

A not so uncommon optimization technique used by apps, it to use a background thread to regularly poll some data and keep a copy always accessible in memory.

Or similarly, it's not uncommon to have a background thread collect and emit metrics at common interval.

With Pitchfork this isn't ideal because you have to be very careful that all background threads are either shutdown or at a safe point when a worker is promoted or when the mold forks a new child.

Idea

Maybe not for 100% of use case, but I believe that in many cases such threads don't actually need to be in the mold nor workers, and could instead be in a separate process.

They also very often don't need an actual dedicated thread, they simply sleep in a loop to perform some action at regular interval.

As such, if we provided a task scheduling API similar to rufus-scheduler (e.g. every 10s), we could run these tasks on a single thread (or a low number of threads) in a dedicated worker, that's never used for promotion, hence for which forking at random points isn't a concern.

For the tasks that need to expose data to workers, they can use a variety of IPC solutions, such as a local key value store, shared memory (with Raindrops), write into file, sqlite3 database etc etc.

[nlicalzi]

Upvoting that this is important, and happy to help where needed/possible

[danmayer]

yes, this could be very useful for a number of things the caching folk are interested in.

[elaineylchan]

Hi @casperisfine hope you are well, want to just ensure that this ticket is still on your radar aiming towards end of the month? :)