misc: handle receiver errors in the event bus #367
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ffarall
approved these changes
Feb 13, 2025
| } | ||
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| pub struct EventBusListener<T: EventBusMessage, E: EventHandler<T>> { | ||
| spawner: TaskSpawner, | ||
| receiver: broadcast::Receiver<T>, | ||
| event_handler: E, | ||
| // Indicate if the event is critical or not and if the receiver can drop it safely or have to panic. |
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Really appreciate the comment here. If you can add comments to other parts of the code here, much appreciated. But I do admit that this whole file is lacking docs.
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In this PR, we handle errors coming from the event bus receiver. It also changes the way we behave in case of
Laggederror.There is 2 possible errors return from the receiver :
Lagged- In this scenario we print a warning message saying that messages have been skipped and we keep reading from the receiver for new messages. This error should only happened when handling events that are p2p. If a peer fill the channel older messages will be dropped and newer will be read. The limit is 2000 events so it will limit the number of tasks being spawned at once avoiding risk of DoS by a peer.Closed- This error will happen if there is no more available sender. It shouldn't happen normally. In this case we print a warning message and leave function.In the scenario the event bus is handling event from the runtime, we are assuming that the limit 2000 is more than enough to never fill the channel because we can handle events faster that the blockchain can accept new transactions.