[pixels-daemon, common, proto] Implement Retina Heartbeat Tracking and consistent hash

[AntiO2]

Features:

• gRPC Service Implementation: Implement the NodeServiceGrpc.NodeServiceImplBase to handle node management requests.

• Etcd Integration: Use Etcd to store and monitor heartbeat keys (Constants.HEARTBEAT_RETINA_LITERAL).

• Heartbeat Watcher: Implement a scheduled task (startEtcdWatcher) that periodically checks the state of Retina nodes registered in Etcd.

• Consistent Hashing Ring Management:

  • Initialize the hashRing (TreeMap) upon startup by loading existing Retina nodes from Etcd.
  • Dynamically update the hashRing (add/remove virtual nodes) based on Etcd watcher changes (node addition/failure).
  • Implement addNodeInternal and removeNodeInternal using the configured bucketNum as the number of virtual nodes, mapping them onto the discrete hash ring.

RPC Endpoint Implementation:

• Implement GetRetinaList to return the list of currently active Retina nodes in the hash ring.
• Implement GetRetinaByBucket to use the consistent hashing logic (tailMap and firstKey) to assign a data key (bucket ID) to the appropriate Retina node.

[bianhq]

Done.