[Bug] Pubsub events go missing

[mzimbres]

I am writing a benchmark for different Redis clients where I know exactly how many pubsub events will be received. When that number is reached the benchmark ends and the app exits. The fred-rs implementation works well up to a certain number of events. After a certain limit not all events are arrive, I guess they go some missing.

The app I wrote which you can use to reproduce the problem can be found here.

Please let me know if fred is being used correctly and efficiently. In the same project you can find the same app implemented with other clients languages, including rust. All of them receive the correct number of events. Thanks.

[aembke]

I'd recommend checking for issues related to lagged receivers: https://docs.rs/tokio/latest/tokio/sync/broadcast/index.html#lagging

You'll need to check the response from rx.recv() for https://docs.rs/tokio/latest/tokio/sync/broadcast/error/enum.RecvError.html#variant.Lagged

If that's the issue you'll likely want to increase the broadcast channel capacity, or you could just try that first and see if it helps, but it's a bit of a numbers game and you'll likely want the lagged error signal either way.

[mzimbres]

There is only one receiver in the app i.e. only one call too

let mut rx = sub.message_rx();

and the events sent to rx are consumed eagerly by the app (there is no way for it to be blocked by any other task)

    let mut n: usize = 0;
    while n++ < EXPECTED_PUSHES {
        let _ = rx.recv().await;
    }

Regardless of the load I guess there should be a way of consuming all events in rx, even if broadcast_channel_capacity is set to 1. How could that be a lagged receiver problem?