[GitHub] lucene-solr pull request #313: SOLR-11924: Added a way to create collection ...

[dennisgove <gi...@git.apache.org>]

Github user dennisgove commented on a diff in the pull request:

    https://github.com/apache/lucene-solr/pull/313#discussion_r176611511
  
    --- Diff: solr/solrj/src/java/org/apache/solr/common/cloud/CollectionSetWatcher.java ---
    @@ -0,0 +1,41 @@
    +/*
    + * 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#registerCollectionSetWatcher(CollectionSetWatcher)}
    + * and called whenever the cluster's collection set changes.
    + */
    +public interface CollectionSetWatcher {
    +
    +  /**
    +   * Called when a collection is created, a collection is deleted or a watched collection's state changes.
    +   *
    +   * Note that, due to the way Zookeeper watchers are implemented, a single call may be
    +   * the result of several collection set changes. Also, multiple calls to this method can be made
    +   * with the same colllection set, ie. without any new updates.
    +   *
    +   * @param collections       the set of collections
    +   *
    +   * @return true if the watcher should be removed
    --- End diff --
    
    What's the case here for removing a watcher, and why is `true` the best option? I'm not totally against it, but a boolean seems an odd choice here. If boolean is used would returning `true` to continue watching be a better choice?


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