Quilkin integration #1293
Description
While the Corrosion PRs and the previous subissues have/will added/add code to the repo, nothing is actually integrated with quilkin.
There are two main pieces to integration.
- Mutation - Cluster/config changes need to be applied to the database, either locally, or in the agent case, sent to a relay and applied to its database, notifying any subscribers
- Subscription - Proxies either subscribe to a relay or to the local database, updating their in-memory cache as they receive subscription events
IMO, since this is a large chunk of new code being integrated, it will make sense to run this in parallel with xDS for some period of time, both to test/compare the implementations that should mostly agree at all times, as well as to just get numbers on timings, eg. how long does an agent sending a cluster update take to be received by all proxy subscribers, as well as I/O numbers eg. how many bytes are being sent to proxies for corrosion vs xDS.
This part will be the most complicated since it introduces runtime overhead of having both corrosion and xDS active in parallel, but again, it's such a large change I would rather take the hit and be confident rather than moving to quickly to remove xDS, the question will be just how long we want/need to run them in parallel before we are confident xDS can be removed.