Help with multi threaded code | Rust Programming Language Community | Page 1

thorn violet Nov 28, 2023, 4:12 PM

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https://github.com/dev-ardi/HN_aggregator

I have some questions about this:

General advice of things that could be done better
why is creating a reqwest::Client so slow (7-9ms)?
Having to manually drop tx and rx feels like I've done an anti pattern somewhere
If I don't call exit(0) the program hangs for a few seconds

I wonder if instead of

    while let Ok(story) = rx.recv() {
        sorted_stories.push(Pair(story.score.unwrap_or_default(), story.id));
        stories.insert(story.id, story);
    }
    drop(rx);

I could do it in another task (for some reason)

    let (sorted_stories, stories) = tokio::spawn(async move {
        while let Ok(story) = rx.recv() {
            sorted_stories.push(Pair(story.score.unwrap_or_default(), story.id));
            stories.insert(story.id, story);
        }
        (sorted_stories, stories)
    })
    .await
    .unwrap();

I don't know how to get rid of the drop(tx) though (I could use a {} block but that's not what I mean

GitHub

GitHub - dev-ardi/HN_aggregator: Hacker News Client

Hacker News Client. Contribute to dev-ardi/HN_aggregator development by creating an account on GitHub.

thorn violet Dec 1, 2023, 6:20 PM

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I'm especially confused about the call to exit()

shrewd beacon Dec 1, 2023, 6:33 PM

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my guess is that a task is still running that has not been closed, so the runtime can't finish

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the code finishes for me without the exit

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you might be able to get how many tasks are in flight with https://docs.rs/tokio/latest/tokio/runtime/struct.RuntimeMetrics.html

RuntimeMetrics in tokio::runtime - Rust

Handle to the runtime’s metrics.

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it might be more natural to make the for where you do the setup and the while where you receive the results in different functions, so the sender/receiver will go out of the scope at the end of it, so no manual drop

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I have no good evidence for this, but on my system at least Client::new does a bunch of calls to openssl, which reads some certificates from the system, so that could be why it takes so much?

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that being said it's not the end of the world, you're not supposed to have too many clients anyway

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