Add new dynamic cluster handling about cdrs-tokio

[conorbros]

Could you elaborate on this?

[krojew]

Available node list should be dynamically updated from server events.

[conorbros]

I am currently working on a PR for that :)

[krojew]

I was planning to rework event handling for that to work first in #32 . Current iterator-based approach works very poorly with async/await.

[conorbros]

Would you be able to give more implementation details? I can look at completing that before I submit my PR if required.

[krojew]

At the moment, no work has been started on this topic, but I'm thinking of replacing whole existing implementation with automatically managing a dedicated extra connection for receiving events, and publishing them via tokio::sync::broadcast.

[conorbros]

At the moment I have the connections stored in an ArcSwap so they can be updated, it is similar to the Scylla driver.

[krojew]

Ok, we can try to merge that first and rework the event system later.

[krojew]

I managed to find time to rework event handling and add cluster metadata handling skeleton. You can take a look at ClusterMetadataManager which should manage contained cluster metadata, which is then passed to load balancers.

[conorbros]

I've done some work on the topology refresh branch of my fork but yours will probably end up being better. There's code for a TopologyReader which you might find useful.

[conorbros]

Or I can take this code and reintegrate my solution?

[krojew]

Sure, rebase your changes on current master. Will welcome a PR with dynamic topology.

[krojew]

Dynamic topology is pretty much done. Now I need to add a load balancer taking advantage of this in #33 .