/*
* Copyright (c) 2008-2017, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.core;
import com.hazelcast.monitor.LocalTopicStats;
import com.hazelcast.topic.TopicOverloadException;
/**
* Hazelcast provides distribution mechanism for publishing messages that are delivered to multiple subscribers,
* which is also known as a publish/subscribe (pub/sub) messaging model. Publish and subscriptions are cluster-wide.
* When a member subscribes for a topic, it is actually registering for messages published by any member in the cluster,
* including the new members joined after you added the listener.
* <p/>Messages are ordered, meaning that listeners(subscribers)
* will process the messages in the order they are actually published. If cluster member M publishes messages
* m1, m2, m3...mn to a topic T, then Hazelcast makes sure that all of the subscribers of topic T will receive
* and process m1, m2, m3...mn in order.
*
* Since Hazelcast 3.5 it is possible to have reliable topics. Normally all topics rely on the a shared eventing system and
* shared threads. With Hazelcast 3.5 it is possible to configure a topic to be reliable and to gets its own
* {@link com.hazelcast.ringbuffer.Ringbuffer} to store events and to gets its own executor to process events. The events
* in the ringbuffer are replicated, so they won't get lost when a node goes down.
*/
public interface ITopic<E> extends DistributedObject {
/**
* Returns the name of this ITopic instance
*
* @return name of this ITopic instance
*/
String getName();
/**
* Publishes the message to all subscribers of this topic
*
* @param message the message to publish to all subscribers of this topic
* @throws TopicOverloadException if the consumer is too slow. Only works in combination with
* reliable topic.
*/
void publish(E message);
/**
* Subscribes to this topic. When someone publishes a message on this topic.
* onMessage() function of the given MessageListener is called. More than one message listener can be
* added on one instance.
*
* @param listener the MessageListener to add.
*
* @return returns the registration id.
* @throws java.lang.NullPointerException if listener is null.
*/
String addMessageListener(MessageListener<E> listener);
/**
* Stops receiving messages for the given message listener. If the given listener already removed,
* this method does nothing.
*
* @param registrationId Id of listener registration.
*
* @return true if registration is removed, false otherwise
*/
boolean removeMessageListener(String registrationId);
/**
* Returns statistics about this topic, like total number of publishes/receives
*
* @return statistics about this topic
*/
LocalTopicStats getLocalTopicStats();
}