public void handle(ObservableQueue queue, Message msg) {
        List<EventExecution> transientFailures = null;
        boolean executionFailed = false;
        try {
            if (isEventMessageIndexingEnabled) {
                executionService.addMessage(queue.getName(), msg);
            }
            String event = queue.getType() + ":" + queue.getName();
            LOGGER.debug("Evaluating message: {} for event: {}", msg.getId(), event);
            transientFailures = executeEvent(event, msg);
        } catch (Exception e) {
            executionFailed = true;
            LOGGER.error("Error handling message: {} on queue:{}", msg, queue.getName(), e);
            Monitors.recordEventQueueMessagesError(queue.getType(), queue.getName());
        } finally {
            if (!executionFailed && CollectionUtils.isEmpty(transientFailures)) {
                queue.ack(Collections.singletonList(msg));
                LOGGER.debug("Message: {} acked on queue: {}", msg.getId(), queue.getName());
            } else if (queue.rePublishIfNoAck() || !CollectionUtils.isEmpty(transientFailures)) {
                // re-submit this message to the queue, to be retried later
                // This is needed for queues with no unack timeout, since messages are removed
                // from the queue
                queue.publish(Collections.singletonList(msg));
                LOGGER.debug("Message: {} published to queue: {}", msg.getId(), queue.getName());
            } else {
                queue.nack(Collections.singletonList(msg));
                LOGGER.debug("Message: {} nacked on queue: {}", msg.getId(), queue.getName());
            }
            Monitors.recordEventQueueMessagesHandled(queue.getType(), queue.getName());
        }
    }
Event Processor is used to dispatch actions configured in the event handlers, based on incoming
events to the event queues.

<p><code>Set conductor.default-event-processor.enabled=false</code> to disable event processing.
core/src/main/java/com/netflix/conductor/core/events/DefaultEventProcessor.java