This PR refactors xds_client to support multiples watches. Those watches can be for the same type and same resource_name.
There's upper level `Client` and lower level `v2client`. Before this change, all logic was in `v2client`, and `Client` was a thin wrapper.
This PR moves some of the functionality from `v2client` to `Client`. New layers:
- Upper level `Client`
- keeps a list of watchers
- provides method `func WatchXXX() (cancel func())`
- has `WatchService()` which involves `LDS` and `RDS`
- handles resources from the xDS responses and dispatch to the watchers
- including multiple watchers for the same resource_name
- keeps cache
- and checks cache for new watches
- Lower level `v2client`
- is a dumb client that
- manages ADS stream
- sends a new xDS request when add/remove watch
- parses xDS responses
- It doesn't call watchers, but forwards all parsed results to upper Client
- handles ACK/NACK
- supports `addWatch(type, name)` and `removeWatch(type, name)`
- instead of `func watchCDS() func()`, which is now moved up to upper `Client`
Also includes other changes:
- Corresponding test changes (some tests for `v2client` were moved to `Client`)
- Method and type renaming
- CDS/EDS -> Cluster/Endpoints
- callback functions all accept updates as non-pointers
Menghan Li
Zou Nengren