mridulm commented on a change in pull request #28618: URL: https://github.com/apache/spark/pull/28618#discussion_r487555163
########## File path: core/src/main/java/org/apache/spark/shuffle/api/metadata/ShuffleOutputTracker.java ########## @@ -0,0 +1,56 @@ +/* + * 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.spark.shuffle.api.metadata; + +/** + * :: Private :: + * + * A plugin that can monitor the storage of shuffle data from map tasks, and can provide + * metadata to shuffle readers to aid their reading of shuffle blocks in reduce tasks. + * <p> + * {@link MapOutputMetadata} instances provided from the plugin tree's implementation of + * {@link org.apache.spark.shuffle.api.ShuffleMapOutputWriter} are sent to + * <p> + * Implementations MUST be thread-safe. Spark will invoke methods in this module in parallel. Review comment: I was not referring to how implementations manage their state/locking (if they have additional state/coordination required, you are right, it has to be handled there - state managed across shuffles as an example for some custom impl). I was referring to what guarantees/expectations that implementations have from spark (`MapOutputTracker` currently) when these methods are invoked. We have to document this, so that implementation can be both aware of the MT-safety guarantees we provide (and at what granularity) - so that they can make reasonable assumptions about what can/cant be done in an implementation. For example, as mentioned above, `registerShuffle` is invoked only with write lock is held for a particular shuffle. While `unregisterShuffle` does not have that guarantee. ---------------------------------------------------------------- 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: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
