eric-maynard commented on code in PR #922: URL: https://github.com/apache/polaris/pull/922#discussion_r1988472892
########## service/common/src/main/java/org/apache/polaris/service/events/PolarisEventListener.java: ########## @@ -0,0 +1,49 @@ +/* + * 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.polaris.service.events; + +/** + * Represents an event listener that can respond to notable moments during Polaris's execution. + * Users can either extend this interface and implement handlers for all events or, for ease, extend + * DefaultPolarisEventListener and only have to handle a subset of events. Event details are + * documented under the event objects themselves. + */ +public interface PolarisEventListener { Review Comment: [SparkListenerInterface](https://github.com/apache/spark/blob/3a872b7ca11faa128a2667de55f6dca13807057a/core/src/main/scala/org/apache/spark/scheduler/SparkListener.scala#L304) is actually `private[spark]` in Scala, but Scala's private is pretty fake anyway. Java or Scala callers can easily access it. > Does it? If the interface PolarisEventListener is public, it's part of the API. If it's part of the API, you cannot add regular methods to it, even if you implement them in DefaultPolarisEventListener. The current implementation gives you both the options to: 1. Implement a listener that extends `PolarisEventListener` and must implement exactly the methods that appear there or fail at build time (or runtime to some ClassNotFoundException if you don't build against the dependency you actually run against). 2. Implement a listener that extends `DefaultPolarisEventListener` and can optionally override various methods of that class. If new methods appear, your already-built artifact may continue working against a different version of polaris than the one you built against. In both cases, you also have the option to go into the code, add new events, and handle those events in your listener(s). <hr> In the end I think @flyrain's suggestion that we "hide" the interface like Spark does is fine; expert users who want it can break glass via fork or something and use it anyway. If the DefaultPolarisEventListener being the more accessible extension point turns out to be problematic in the future (e.g. users are surprised by new events being ignored) then we can always expose the interface and update our guidance. In general, I expect anyone deploying a custom listener to be a power-user. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
