Relay HA
High Availability of Relay Server with the following two approaches:
Two or more Relay Servers read from the Source Data Source
Two or more Relay Servers read from the Source Data Source. The clients connect to Relay Servers via a HTTP LB. Since the requests from clients are over HTTP one of the Relay Servers or both can be serving the request based on the configuration in the LB. When one Relay goes down the other can still handle the requests.
Relay Chaining with HA using Leader Follower model.
A producer "Relay Producer" can be built that reads from another Relay. A Relay with this producer can act as normal Relay for Clients. This Relay can have both producers, Source Producer and Relay Producer, but only one is active at a time. There can be two Relays, Leader Relay and Follower Relay. On Leader Relay the source producer is active. On follower relay the relay producer is active. Clients can read from either relay via a LB. Leader/Follower election is done via Helix Leader/Follower algorithm. In fact we can have total of N relays with k leaders and n-k followers. The clients can either read from each relay via a LB or act as spectators so that they know which relay is the leader and connect to that Relay. This approach is yet been implemented.
