alibaba/nacos · error · IllegalStateException

Publisher does not start

Error message

Publisher does not start

What it means

Thrown by DefaultPublisher.checkIsStart() when the publisher's initialized flag is still false — i.e. start() was never called, or the object was constructed but not started before an event was published. It is an IllegalStateException (not a runtime Nacos exception) signalling the event-dispatch thread is not alive.

Source

Thrown at common/src/main/java/com/alibaba/nacos/common/notify/DefaultPublisher.java:154

    }
    
    @Override
    public boolean publish(Event event) {
        checkIsStart();
        boolean success = this.queue.offer(event);
        if (!success) {
            LOGGER.warn(
                "Unable to plug in due to interruption, synchronize sending time, event : {}",
                event);
            receiveEvent(event);
            return true;
        }
        return true;
    }
    
    void checkIsStart() {
        if (!initialized) {
            throw new IllegalStateException("Publisher does not start");
        }
    }
    
    @Override
    public void shutdown() {
        this.shutdown = true;
        this.queue.clear();
        // Interrupt the thread to stop processing events: queue.take().
        this.interrupt();
    }
    
    public boolean isInitialized() {
        return initialized;
    }
    
    /**
     * Receive and notifySubscriber to process the event.
     *

View on GitHub (pinned to 9b989acdf1)

Solutions

1. Ensure publisher.start() is called (and returns) before any publish; in normal usage, rely on NotifyCenter which manages publisher lifecycle.
2. Do not construct DefaultPublisher directly — register subscribers through NotifyCenter.addSubscriber so the framework starts the publisher.
3. In tests, call publisher.start() in @Before and publish only after the thread is alive; check publisher.isInitialized() if unsure.
4. Avoid publishing after shutdown(); guard with a lifecycle check or recreate the publisher.

Example fix

// before
DefaultPublisher pub = new DefaultPublisher(name, listener);
pub.publish(event); // IllegalStateException: not started

// after
DefaultPublisher pub = new DefaultPublisher(name, listener);
pub.start();
pub.publish(event);

if (!publisher.isInitialized()) {
    publisher.start();
}
publisher.publish(event);

boolean isPublisherReady(DefaultPublisher p) {
    return p != null && p.isInitialized();
}

try {
    publisher.publish(event);
} catch (IllegalStateException e) {
    log.error("Publisher {} not started", publisher.getName(), e);
    throw e;
}

When it happens

Trigger: Calling publisher.publish(event) or any path that calls checkIsStart() on a DefaultPublisher that was constructed via new DefaultPublisher(...) but whose start() was never invoked; using a publisher after shutdown() reset its thread state; accessing a publisher from NotifyCenter before its lazy init completed.

Common situations: Custom Event/Subscriber wiring that creates a DefaultPublisher directly instead of going through NotifyCenter; a race where shutdown() runs concurrently; a unit test that instantiates a publisher and immediately publishes without start(); the NotifyCenter publisher pool not yet initialized at boot.

Related errors

• The subscriber has no event publisher
• PARAMETER_MISSING
• RESOURCE_CONFLICT
• 20005
• NacosLockService has been shut down

AI-assisted analysis of alibaba/nacos@9b989acdf1 (2026-08-14). Data as JSON: /api/errors/e45f1b6631ba568e. Report an issue: GitHub.