Lifecycle Hooks

Lifecycle hooks expose Rabbit Relay operational events.

They are useful for logging, metrics, OpenTelemetry, debugging, and production visibility.

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Basic usage

const broker = new RabbitMQBroker("orders-service");

broker.on("consumer.started", (event) => {
  console.log("consumer started", event.queue);
});

broker.on("retry.scheduled", (event) => {
  console.log("retry scheduled", event.retryCount, event.delayMs);
});

Returned broker interfaces also support lifecycle hooks:

const sub = await broker.queue("orders.q").exchange("orders.ex");

sub.on("consumer.started", (event) => {
  console.log(event.queue);
});

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Supported events

Event	Meaning
reconnect	Broker reconnected
topology.asserted	Exchange/queue/binding topology was asserted
consumer.started	Consumer started
consumer.stopped	Consumer stopped
publish.failed	Publish failed after retry attempt
retry.scheduled	A retry was scheduled
broker.closed	Broker was closed

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Retry scheduled example

broker.on("retry.scheduled", (event) => {
  console.log({
    queue: event.queue,
    exchange: event.exchange,
    routingKey: event.routingKey,
    retryCount: event.retryCount,
    attempts: event.attempts,
    delayMs: event.delayMs,
  });
});

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Publish failed example

broker.on("publish.failed", (event) => {
  console.error("publish failed", {
    exchange: event.exchange,
    routingKey: event.routingKey,
    eventName: event.eventName,
    error: event.error,
  });
});

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Lifecycle hooks vs plugins

Feature	Lifecycle Hooks	Plugins
Scope	Broker instance	Process-wide
Focus	Operations events	Message lifecycle
API	broker.on(...)	pluginManager.register(...)
Best for	logging, metrics, tracing, operations	cross-cutting message behavior

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Error behavior

If a lifecycle hook throws:

• the error is caught and logged
• Rabbit Relay continues running
• the broker operation is not blocked

Keep hooks lightweight and non-blocking.

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Summary

• Lifecycle hooks expose broker operations
• Useful for logging, metrics, and tracing
• Local to a broker instance
• Safe failure behavior
• Foundation for the OpenTelemetry adapter