Implement stream listener #20
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| E: std::fmt::Debug + Send, | ||
| S: Unpin + Send + Stream<Item = Result<I, E>> + 'static, | ||
| { | ||
| let cancelation_token = CancellationToken::new(); |
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I had the idea of creating the CancellationToken in the GenServer on initialization. And every time a listener or a timer is spawned to interact with the GenServer it should request it for the CancellationToken to reuse the same one.
Then, it's the GenServer responsibility to cancel the token on termination. That way, graceful cancellation is transparent for the external process.
Anyway, we can try to implement that on this PR, or ticket it for a future improvement.
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I agree that it'd be a good idea to have the cancellation token inside of the gen server, considering this change would also requiere a change in the timer implementation, I believe we should make this change on a separate PR.
I'll branch from this one and start work on it ASAP.
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Yeah, given GenServer is just a Trait, I guess we should put the token in the GenServerHandler, right?
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Yes, I've taken an approach of that kind, see the PR here
concurrency/src/tasks/stream.rs
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| let cloned_token = cancelation_token.clone(); | ||
| let join_handle = spawned_rt::tasks::spawn(async move { | ||
| loop { | ||
| if cloned_token.is_cancelled() { |
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This is not the way an async CancellationToken is supposed to be used:
stream.next() is a future and execution can be held at that point, even when the token gets cancelled. We should use futures::future::select like we do on timer module (or tokio::select! if we decide to allow macros) to await on both futures at the same time. See graceful shutdown
| @@ -8,5 +8,9 @@ spawned-rt = { workspace = true } | |||
| tracing = { workspace = true } | |||
| futures = "0.3.1" | |||
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| [dev-dependencies] | |||
| tokio-stream = { version = "0.1.17" } | |||
| tokio = { version = "1", features = ["full"] } | |||
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One hidden goal we have is not to depend on tokio in more than one place. This deps should be in rt crate, and reexported so we can use them in concurrency crate
(that way, if we ever plan to replace the runtime, we do it in a single place, ideally)
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This imports are only used for testing (inside of the streaming tests more specifically). They are meant to show intercompatibility with tokio (e.g we receive a broadcast channel and need to make use of it inside of spawned).
Add
spawn_listenerfunction to crate, this function is used to enable communication betweenGenServers andStreams.In this PR adds a new re-export:
BroadcastStreamWhich is used to convert (wrap) their kind of receiving channel into a stream compatible with
spawn_listener.Threads implementation is no longer maintained, so there's nothing added to that concurrenc method.
Closes #17