murblanc commented on a change in pull request #1684: URL: https://github.com/apache/lucene-solr/pull/1684#discussion_r482463350
########## 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: @sigram Keep in mind it's not subclassing just for the pleasure of subclassing. In this example of `createCoreCountKey()`, we end up building an `AbstractNodePropertyKey.CoreCountImpl` and that's where the definition is that this key will correspond to `ImplicitSnitch.CORES`. If we make creation code generic, we'll have to move the actual differences in implementation to somewhere else. Another key create by `createMetricKey` does even more in `AbstractNodePropertyKey.NodeMetricImpl` since it translates the abstracted registry (from `NodeMetricRegistry`) into the actual registry and assembles the metric name. In other words, there's specific code to write regardless for each new key type assuming we don't want to expose the internal implementation of Solr (and parameters such as `"metrics:"` and `"totaldisk"` etc used in messages). ---------------------------------------------------------------- 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
