package org.infinispan.notifications.cachelistener.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.infinispan.distribution.DistributionManager;
import org.infinispan.distribution.ch.ConsistentHash;
import org.infinispan.notifications.IncorrectListenerException;
import org.infinispan.notifications.cachelistener.event.Event;
import org.infinispan.notifications.cachelistener.event.TopologyChangedEvent;

/**
 * This annotation should be used on methods that need to be notified when the {@link ConsistentHash} implementation
 * in use by the {@link DistributionManager} changes due to a change in cluster topology.  This is only fired
 * in a {@link org.infinispan.configuration.cache.CacheMode#DIST_SYNC} or {@link org.infinispan.configuration.cache.CacheMode#DIST_ASYNC} configured cache.
 * <p/>
 * Methods annotated with this annotation should accept a single parameter, a {@link TopologyChangedEvent} otherwise a
 * {@link IncorrectListenerException} will be thrown when registering your listener.
 * <p/>
 * Note that methods marked with this annotation will be fired <i>before</i> and <i>after</i> the updated {@link ConsistentHash}
 * is installed, i.e., your method will be called twice, with {@link Event#isPre()} being set to <tt>true</tt> as well
 * as <tt>false</tt>.
 * <p/>
 *
 * @author Manik Surtani
 * @see org.infinispan.notifications.Listener
 * @since 5.0
 */
// ensure this annotation is available at runtime.
@Retention(RetentionPolicy.RUNTIME)
// ensure that this annotation is applied to classes.
@Target(ElementType.METHOD)
public @interface TopologyChanged {
}
