Service Discovery Tasks

[kingster]

Based on #76 the following tasks are the next steps

Enables auto discover of active slaves for clients and active masters for slaves to replication from
Enables Issue - #73

More details and LLD here

keywords

1. region - an isolated data space. a node can have multiple regions belonging to multiple databases or multiple shards within a database. a node can be leader of 1 region, follower of another and slave of yet another
2. leader - raft leader
3. master - node being replication from by a slave. could be a leader / follower or another slave too for all practical purposes

Next steps

• Envoy and XDS changes to serve data from SD #89
• RaftGroups : Enable multiple regions in a node #92
• Enable accurate/local-dc leader / follower identification
• DKV Async Slaves - Autodiscover / Autoswitch Repl Master #73
• Enable slaves to switch masters when masters are temporarily unavailable #82
• Refactor interfaces to seperate grpc interface from internal dkv data plane, leader/follower, master, slave to avoid making apis like getStatus, prefixMultiGet public and to create better contracts across these types of DKVServer
• Jepsen tests on linearizable / sequential / eventual consistent reads