| /* |
| * 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 there is a change in the collection state |
| * <em>or</em> in the list of liveNodes. |
| * |
| * @see DocCollectionWatcher |
| */ |
| public interface CollectionStateWatcher { |
| |
| /** |
| * Called when either the collection we are registered against has a change of state <em>or</em> |
| * there is a change to the live nodes of our collection. |
| * |
| * <p>Note that, due to the way Zookeeper watchers are implemented, a single call may be the |
| * result of several state changes. Also, multiple calls to this method can be made with the same |
| * state, ie. without any new updates. |
| * |
| * @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); |
| } |
