Package com.onec.cluster.pg

Class PostgresClusterEventBus

java.lang.Object

com.onec.cluster.pg.PostgresClusterEventBus

All Implemented Interfaces:

ClusterEventBus, org.springframework.beans.factory.DisposableBean, org.springframework.beans.factory.InitializingBean

public class PostgresClusterEventBus
extends Object
implements ClusterEventBus, org.springframework.beans.factory.InitializingBean, org.springframework.beans.factory.DisposableBean

ClusterEventBus backed by Postgres LISTEN/NOTIFY — the default cross-node transport, needing no infrastructure beyond the database the app already uses.

Publish is a short pooled SELECT pg_notify(channel, json). Receive runs on one daemon thread holding a dedicated connection that LISTENs on the channel and blocks in PGConnection.getNotifications(int); on a dropped connection it reconnects with capped exponential backoff. Events the node published itself are filtered out by ClusterEvent.originNodeId() (Postgres echoes a NOTIFY back to the publisher's own LISTEN, and the publisher already fanned the change out to its local SSE clients).

This is a best-effort live-UI signal: a notice missed during a reconnect is acceptable (browsers re-fetch on their next interaction). The held listener connection costs one slot from the datasource pool for the bus's lifetime.

Constructor Summary

Constructors

Constructor	Description
PostgresClusterEventBus(DataSource dataSource, com.fasterxml.jackson.databind.ObjectMapper mapper, OnecClusterProperties props)

Method Summary

Modifier and Type	Method	Description
void	afterPropertiesSet()
void	destroy()
String	nodeId()	The id this node stamps on published events and filters incoming echoes against.
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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.onec.cluster.ClusterEventBus

isDistributed

Constructor Details

PostgresClusterEventBus

public PostgresClusterEventBus(DataSource dataSource,
 com.fasterxml.jackson.databind.ObjectMapper mapper,
 OnecClusterProperties props)

Method Details

afterPropertiesSet

public void afterPropertiesSet()

Specified by:

afterPropertiesSet in interface org.springframework.beans.factory.InitializingBean

publish

public void publish(ClusterEvent event)

Description copied from interface: ClusterEventBus

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).

Specified by:

publish in interface ClusterEventBus

subscribe

public void subscribe(Consumer<ClusterEvent> sink)

Description copied from interface: ClusterEventBus

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.

Specified by:

subscribe in interface ClusterEventBus

nodeId

public String nodeId()

The id this node stamps on published events and filters incoming echoes against.

destroy

public void destroy()

Specified by:

destroy in interface org.springframework.beans.factory.DisposableBean