/*
* 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.common.cloud;
import java.util.Set;
/**
* Callback registered with {@link ZkStateReader#registerCollectionStateWatcher(String, CollectionStateWatcher)}
* and called whenever the collection state changes.
*/
public interface CollectionStateWatcher {
/**
* Called when the collection we are registered against has a change of state
*
* Note that, due to the way Zookeeper watchers are implemented, a single call may be
* the result of several state changes
*
* @param liveNodes the set of live nodes
* @param collectionState the new collection state (may be null if the collection has been
* deleted)
*
* @return true if the watcher should be removed
*/
boolean onStateChanged(Set<String> liveNodes, DocCollection collectionState);
}