murblanc commented on a change in pull request #1758: URL: https://github.com/apache/lucene-solr/pull/1758#discussion_r498957288
########## File path: solr/core/src/java/org/apache/solr/cluster/events/ClusterEventProducer.java ########## @@ -0,0 +1,100 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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 org.apache.solr.cluster.events; + +import org.apache.solr.cloud.ClusterSingleton; + +import java.util.Collections; +import java.util.Map; +import java.util.Objects; +import java.util.Set; +import java.util.concurrent.ConcurrentHashMap; + +/** + * Component that produces {@link ClusterEvent} instances. + */ +public interface ClusterEventProducer extends ClusterSingleton { + + String PLUGIN_NAME = "clusterEventProducer"; + + default String getName() { + return PLUGIN_NAME; + } + + /** + * Returns a modifiable map of event types and listeners to process events + * of a given type. + */ + Map<ClusterEvent.EventType, Set<ClusterEventListener>> getEventListeners(); + + /** + * Register an event listener for processing the specified event types. + * @param listener non-null listener. If the same instance of the listener is + * already registered it will be ignored. + * @param eventTypes non-empty array of event types that this listener + * is being registered for. If this is null or empty then all types will be used. + */ + default void registerListener(ClusterEventListener listener, ClusterEvent.EventType... eventTypes) throws Exception { + Objects.requireNonNull(listener); + if (eventTypes == null || eventTypes.length == 0) { + eventTypes = ClusterEvent.EventType.values(); + } + for (ClusterEvent.EventType type : eventTypes) { + Set<ClusterEventListener> perType = getEventListeners().computeIfAbsent(type, t -> ConcurrentHashMap.newKeySet()); + perType.add(listener); + } + } + + /** + * Unregister an event listener. + * @param listener non-null listener. + */ + default void unregisterListener(ClusterEventListener listener) { + Objects.requireNonNull(listener); + getEventListeners().forEach((type, listeners) -> { + listeners.remove(listener); + }); + } + + /** + * Unregister an event listener for specified event types. + * @param listener non-null listener. + * @param eventTypes event types from which the listener will be unregistered. If this + * is null or empty then all event types will be used + */ + default void unregisterListener(ClusterEventListener listener, ClusterEvent.EventType... eventTypes) { + Objects.requireNonNull(listener); + if (eventTypes == null || eventTypes.length == 0) { + eventTypes = ClusterEvent.EventType.values(); + } + for (ClusterEvent.EventType type : eventTypes) { + getEventListeners() + .getOrDefault(type, Collections.emptySet()) + .remove(listener); + } + } + + /** + * Fire an event. This method will call registered listeners that subscribed to the + * type of event being passed. + * @param event cluster event + */ + default void fireEvent(ClusterEvent event) { Review comment: Firing (publishing) events is definitely needed in solr core where events are created. Do we need to couple the publishing of events and managing the consumption of events as done here, or maybe have a simple publishing interface (with this single method) and a separate one for implementing the even distribution logic? This could eventually allow keeping in Solr core the things that really belong there (creating events related to solr internal state change and publishing them) while allowing to move the event bus logic outside of solr core. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
