Background

The Apache Ratis HA module currently identifies peers positionally:

• HA_SERVER_LIST is a comma-separated list of host:raftPort:httpPort:priority entries
• Each node's slot is derived from the numeric suffix of HA_SERVER_NAME (e.g. ArcadeDB_0 -> peer index 0)
• Display names shown in logs and Studio are synthesized as <localPrefix><sep><index> using the local node's name prefix

This works well for K8s StatefulSet deployments (arcadedb-0, arcadedb-1, ...) but is confusing in two cases:

1. Operators who deploy with heterogeneous names (e.g. frankfurt, london, nyc) must still embed a numeric suffix, and the displayed peer names get rebuilt from the local prefix and don't reflect the configured names.
2. The mapping between HA_SERVER_NAME and the position in HA_SERVER_LIST is implicit. If they get out of sync, a node claims the wrong slot.

Proposal

Add an optional name@ prefix to each entry in HA_SERVER_LIST. Fully backward compatible: entries without @ keep their current behavior; mixed clusters work; @ does not appear in any current valid format so detection is unambiguous.

HA_SERVER_LIST=frankfurt@10.0.0.1:2424:2480,london@10.0.0.2:2424:2480,nyc@10.0.0.3:2424:2480

Resolution rules:

• If a peer entry has name@, the local node identifies its slot by matching HA_SERVER_NAME against the peer name first.
• If no name match is found, fall back to the existing prefix_N / prefix-N suffix resolution.
• Display names use the configured peer name when present; otherwise the existing positional synthesis is used.
• Names must be unique within the cluster (validated at parse time).

Affected components

• HA_SERVER_LIST parser (RaftPeerAddressResolver.parsePeerList)
• Local peer resolution (RaftPeerAddressResolver.findLocalPeerId)
• Display-name building (RaftHAServer constructor + getPeerDisplayName)
• Dynamic membership: optional name parameter on addPeer admin command (POST payload field) so peers added at runtime also get a friendly name in logs/Studio
• HAServerPlugin interface: optional 3-arg addPeer(peerId, address, name) default that delegates to the 2-arg version, so non-Raft implementations keep working

Out of scope

• No wire-level name exchange between nodes is needed: HA_SERVER_LIST is already a cluster-wide setting, so each node already knows the configured names.
• HA_SERVER_NAME itself does not need to change. With named peers, its numeric suffix simply becomes optional.