How to run background jobs? (lemmy.world)

submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]

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Is there any library for the queueing mechanism?

What's used by the most - Cron? But a task or rather script executed by Cron won't access to the context of an application. Meaning, a task will have be an independent unit. Whereas I want is a library to use inside a project such that it'll have access to everything.

Anything similar to Sidekiq exist in Rust?

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[-] [email protected] 1 points 1 year ago* (last edited 1 year ago)

For my project I just run them. I'm using async so it is just spawning a task in the background, but you can do the same with threads. Don't underestimate the number of threads that you can run on a modern computer.

If you want some sort of throttling you can stuff tasks into a queue and just run N background threads pulling them off an processing them.

If you need durability then you start to have more trouble. This is where I would start looking at a library. IDK if there are any libraries that handle logging, retries and similar, but if not you can probably get the basics down pretty easily.

[-] [email protected] 0 points 1 year ago* (last edited 1 year ago)

For my project I just run them.

How would you "just run" a task every 30 minutes? Every 5 hours? Once a day?

[-] [email protected] 2 points 1 year ago

std::thread::spawn(|| {
    loop {
        std::thread::sleep(std::time::Duration::from_secs(30*60));
        do_job();
    }
});

Works pretty well. Maybe add a bit of code to crash the whole process on panic or some other logging. Wastes a few KiB of memory per loop but probably not a major issue. Doing this with async will waste only the tiniest amount of memory.

[-] [email protected] 1 points 1 year ago

@kevincox How do you stop the job? Do you use channels like in Go?

[-] [email protected] 1 points 1 year ago

It depends. Sometimes you can just put an exit call at the end of main to kill the thread. If you want to attempt graceful shutdown then usually I just use a boolean shutdown flag. Then the loop becomes while !shutdown.get() {

[-] [email protected] 0 points 1 year ago* (last edited 1 year ago)

what if one of the calls crashes? how would you re-run it?

[-] [email protected] 1 points 1 year ago

Best option is probably to add a wrapper around the thread that re-spawns it. But you can also just catch panics in the loop.

[-] [email protected] 0 points 1 year ago* (last edited 1 year ago)

How would you re-run it multiple times then? An internal should be progressively greater. How would you terminate it if it continues to produce an exception?

this post was submitted on 18 Sep 2023

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