Introduction to Event Engine Cluster Plugin

@sullux/event-engine-cluster-plugin delivers leaderless, fault-tolerant replication across distributed @sullux/event-engine instances.

Built on a 2-of-3 Quorum Mesh Consensus model combined with tamper-evident SHA-256 Hash Chaining, it guarantees strong consistency, partition tolerance, and automatic catch-up recovery across peer nodes without requiring heavy external coordination services like Raft or ZooKeeper.

Architectural Principles

• Leaderless 2-of-3 Quorum: Any node in the cluster can accept ingress requests. Ingress succeeds as soon as a quorum of peers (e.g. 2 out of 3 nodes) acknowledge the proposed event.
• Cryptographic Hash Chain: Every replicated event computes an immutable SHA-256 hash chaining back to the previous committed event hash (event.prevHash), making tampering or out-of-order execution immediately detectable.
• Partition Resilience: Isolated nodes that cannot achieve quorum reject local writes safely, preserving ledger integrity until network partitions resolve.
• Streamlined Catch-Up: Offline or reconnected nodes query missing hash ranges via cluster.sync.requested and roll forward automatically.

The Quorum Replication Cycle

  Node A (Coordinator)                Node B (Peer)                  Node C (Peer)
         │                                  │                              │
         ├────── 1. Proposal (event) ───────┼─────────────────────────────►│
         │                                  │                              │
         │◄───── 2. Ack (hash) ─────────────┤                              │
         │                                  │                              │
  [Quorum 2/3 Met!]                         │                              │
         │                                  │                              │
         ├────── 3. Commit Ingress ─────────┼─────────────────────────────►│
         │                                  │                              │