murblanc commented on a change in pull request #1684: URL: https://github.com/apache/lucene-solr/pull/1684#discussion_r466727764
########## File path: solr/core/src/java/org/apache/solr/cluster/placement/PropertyKeyFactory.java ########## @@ -0,0 +1,61 @@ +/* + * 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.placement; + +/** + * Factory used by the plugin to create property keys to request property values from Solr.<p> + * + * Building of a {@link PropertyKey} requires specifying the target (context) from which the value of that key should be + * obtained. This is done by specifying the appropriate {@link PropertyValueSource}.<br> + * For clarity, when only a single type of target is acceptable, the corresponding subtype of {@link PropertyValueSource} is used instead + * (for example {@link Node}). + */ +public interface PropertyKeyFactory { + /** + * Returns a property key to request the number of cores on a {@link Node}. + */ + PropertyKey createCoreCountKey(Node node); Review comment: If we add new types of `PropertyKeys` we will have to add implementations for these new keys. Wouldn't we need to touch the Solr codebase anyway? Clients (plugins) using the interface would have to know about the new implementation classes and update their code to use them. Technically they could pass a class name through config or other means to use new implementations without code change, but is it a realistic scenario? What would they do with these keys? What are the values these keys will fetch and how will they be used? I'm not against making generic and highly flexible code but only if it's really needed. So if you have a real use case in mind that we should support, I'm open. Otherwise I'd rather keep things strongly typed for now (and as long as we only add stuff to these interfaces we're not breaking anything so we can add later). ---------------------------------------------------------------- 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
