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Supervisors cannot be stopped (formerly "Supervisor causes panic") #27

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hoodie opened this issue Sep 26, 2020 · 1 comment · Fixed by #28 · May be fixed by #48
Open

Supervisors cannot be stopped (formerly "Supervisor causes panic") #27

hoodie opened this issue Sep 26, 2020 · 1 comment · Fixed by #28 · May be fixed by #48

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@hoodie
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hoodie commented Sep 26, 2020

Hi there,
thanks for the nice crate 👍
I was trying out Supervisors though and I don't quite understand how to use them. I seem to always get a panic inside of futures-channels mpcs code when I launch one.

here is a minimal example

use xactor::Actor;

pub struct ServiceA {
    pub session_id: u32,
}

#[async_trait::async_trait]
impl Actor for ServiceA { }

#[async_std::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    xactor::Supervisor::start(|| ServiceA { session_id: 4 }).await?;

    Ok(())
}

this causes a panic with the following messages for me

thread 'async-std/runtime' panicked at 'Receiver::next_message called after `None`', /home/hoodie/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-channel-0.3.5/src/mpsc/mod.rs:1141:41

do you have any idea what could be the reason for this?

thank you
@hoodie
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hoodie commented Sep 27, 2020

Hi there, seems I was holding it wrong.
Of course what I forgot to hold and await the Addr that is being returned from start like this:

    let service_supervisor = xactor::Supervisor::start(|| ServiceA { session_id: 4 }).await?;
    service_supervisor.wait_for_stop().await;

how every this reveals another issue, namely that supervisors cannot be stopped 😉 and if they are dropped (as in my original example) they simply cause the Receiver::next_message in futures-channel mpsc to panic.

@hoodie hoodie changed the title Supervisor causes panic Supervisors cannot be stopped (formerly "Supervisor causes panic") Sep 27, 2020
@payload payload mentioned this issue Sep 27, 2020
Merged
sunli829 added a commit that referenced this issue Sep 28, 2020
@sunli829
Merge pull request #28 from payload/fix/supervisor-panic
f36533d 
Don't call rx.next after receiving None, fixes #27
@sunli829 sunli829 reopened this Sep 28, 2020
@hoodie hoodie linked a pull request Oct 10, 2021 that will close this issue
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@hoodie @sunli829