Package com.onec.cluster

Interface ClusterEventBus

All Known Implementing Classes:

NoOpClusterEventBus, PostgresClusterEventBus

public interface ClusterEventBus

Pluggable SPI for delivering ClusterEvents across the nodes of a horizontally-scaled deployment — the mechanism that keeps live-UI updates in sync when more than one instance runs behind a load balancer.

It is swappable exactly like com.onec.ui.media.MediaStorage: the framework wires a NoOpClusterEventBus when nothing better is available, onec-cluster-starter supplies a Postgres LISTEN/NOTIFY default on a Postgres datasource, and a commercial build can replace either by exposing its own ClusterEventBus bean (e.g. Kafka- or Redis-backed), which the auto-configuration's @ConditionalOnMissingBean default then steps aside for.

This is a best-effort live-UI signal, not a guaranteed-delivery event log. An event dropped during a reconnect is acceptable — the browser re-fetches the affected surface on its next interaction. Durable, exactly-once domain-event distribution is the job of the outbox relay (com.onec.messaging.OutboxWriter + onec-kafka-starter), not this bus.

Method Summary

Modifier and Type	Method	Description
default boolean	isDistributed()	Whether this bus actually crosses node boundaries.
void	publish(ClusterEvent event)	Publish a change to peer nodes.
void	subscribe(Consumer<ClusterEvent> sink)	Register a sink invoked for events that originated on other nodes.

Method Details

publish

void publish(ClusterEvent event)

Publish a change to peer nodes. Fan-out to the publishing node's own SSE clients has already happened synchronously on the local event path, so an implementation that echoes the event back to its own subscribers must let them filter it by ClusterEvent.originNodeId().

The implementation stamps the event's ClusterEvent.originNodeId() with its own node id before sending (see ClusterEvent.withOrigin(java.lang.String)); callers may leave that field null (as ClusterEvent.entityChanged(java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String) does).

subscribe

void subscribe(Consumer<ClusterEvent> sink)

Register a sink invoked for events that originated on other nodes. A bus must not invoke the sink for the local node's own events (see ClusterEvent.originNodeId()). May be called more than once to attach multiple sinks.

isDistributed

default boolean isDistributed()

Whether this bus actually crosses node boundaries. false for NoOpClusterEventBus (single-node / non-Postgres dev), true for a real distributed implementation. Useful for diagnostics and for callers that want to log the active topology at startup.