client_listener: Explicitly queue outgoing messages to guarantee order #28
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progval
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Spawning a task on each event to send implicitly used tokio as an unbounded queue that doesn't actually preserve order. This could cause issues, such as ConnectionData being sent after the first message, which violates assumptions down the line.
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Aug 25, 2023
| @@ -106,6 +103,16 @@ impl ListenerProcess { | |||
| } | |||
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| select! { | |||
| event = self.event_out_buffer_rx.recv() => | |||
| { | |||
| let event_sender = Arc::clone(&self.event_sender); | |||
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No need for these clone operations if you're not spawning a subtask
| { | ||
| let event_sender = Arc::clone(&self.event_sender); | ||
| let shutdown_flag = Arc::clone(&self.shutdown_flag); | ||
| if let Err(e) = event_sender.send(&event.unwrap()).await { |
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Sending here will still block the main task if send() blocks, which brings back the deadlock issue that caused me to spawn sends in the first place.
If we're going to use an unbounded channel to make sure that this task never blocks, then there needs to be a separate task that reads it and forwards to the socket; if we're doing the socket writes in this task then we can do them directly and don't need the extra channel.
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Rewritten in #29 (from scratch, though they turned out to look quite similar) |
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Spawning a task on each event to send implicitly used tokio as an unbounded queue that doesn't actually preserve order.
This could cause issues, such as ConnectionData being sent after the first message, which violates assumptions down the line.