WIP: node: Update p2panda to new API #195
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jsparber
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| let abort_handle = spawn(async move { | ||
| while let Ok(event) = topic_rx.recv().await { | ||
| while let Some(Ok(event)) = topic_rx.next().await { |
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What's the error that can happen on each item of the stream? Is the error something persistent, or can we just go to the next item in the stream when we see an error?
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Same thing for the GossipSubscription
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Looking at the code GossipSubscription error is only https://docs.rs/tokio-stream/latest/tokio_stream/wrappers/errors/enum.BroadcastStreamRecvError.html and it will be fine to keep reading after an error. I think the item stream should return the specific error not an enum of all errors.
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Now looked also at the SyncSubscription is the same as the GossipSubscription. So the only error that can happen is https://docs.rs/tokio-stream/latest/tokio_stream/wrappers/errors/enum.BroadcastStreamRecvError.html. I wonder if that error couldn't be handled internally.
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Now looked also at the
SyncSubscriptionis the same as theGossipSubscription. So the only error that can happen ishttps://docs.rs/tokio-stream/latest/tokio_stream/wrappers/errors/enum.BroadcastStreamRecvError.html. I wonder if that error couldn't be handled internally.
I'm actually touching on this area for my work to remove the unwanted trait leakage from p2panda-sync. I will make it so that BroadcastStreamReccError is returned from the sync subscription. I could do the same with gossip as well.
What did you mean by handling the error internally though?
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The error indicates that messages have been dropped, which I believe is important to know, even though the user doesn't have a chance to recover from this in the gossip case?
However, this is an issue with this particular mpmc channel implementation of tokio. We could switch to flume or something else which offers bounded channels who will instead apply backpressure rather than dropping items. I believe we can then also hide the https://docs.rs/flume/latest/flume/enum.RecvError.html error since it'll be equal to a Stream termination (yielding None). Looks like they implement it exactly like that: https://docs.rs/flume/latest/src/flume/async.rs.html#573
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What did you mean by handling the error internally though?
I mean not exposing the error to the consumer at all, and make sure internally that it doesn't happen or that it's handled. For the consumer it's quite unclear how to handle the error, is there a way to request missed operations because of the slow read?
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Here's an issue @sandreae and I found while testing this together:
Any ideas, @jsparber ? |
Could make sense even though it might make entering a document slower. Anyhow, this doesn't seam relevant here. |
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