mccheah commented on a change in pull request #25007: [SPARK-28209][CORE][SHUFFLE] Proposed new shuffle writer API URL: https://github.com/apache/spark/pull/25007#discussion_r307061612
########## File path: core/src/main/java/org/apache/spark/shuffle/api/TransferrableWritableByteChannel.java ########## @@ -0,0 +1,59 @@ +/* + * 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; + +import java.io.Closeable; +import java.io.IOException; + +import java.nio.channels.FileChannel; +import java.nio.channels.WritableByteChannel; +import org.apache.spark.annotation.Private; + +/** + * :: Private :: + * Represents an output byte channel that can copy bytes from input file channels to some + * arbitrary storage system. + * <p> + * This API is provided for advanced users who can transfer bytes from a file channel to + * some output sink without copying data into memory. Most users should not need to use + * this functionality; this is primarily provided for the built-in shuffle storage backends + * that persist shuffle files on local disk. + * <p> + * For a simpler alternative, see {@link ShufflePartitionWriter}. + * + * @since 3.0.0 + */ +@Private +public interface TransferrableWritableByteChannel extends Closeable { + + /** + * Copy all bytes from the source readable byte channel into this byte channel. + * <p> + * This method should block until all of the bytes from the source (that is, up until + * numBytesToTransfer) are available in the output storage layer. + * + * @param source File to transfer bytes from. Do not call anything on this channel other than Review comment: Ah I didn't see your follow-up comment. I'm not as fond of passing the resource back to the plugin to ask the plugin to close it? I'm not sure, that isn't a very common programming idiom with respect to streams and resources - usually the `close` method is attached to the closeable resource itself. I liked the channel wrapper abstraction. We used to have the `close` method attached to the `ShufflePartitionWriter` and only closed the partition writer itself and not the channel, but that seemed prone to error on the plugin writer's side - since the partition writer returns a closeable resource itself, should the plugin expect the closeable resource it returns to be closed, or should it expect `ShufflePartitionWriter#close` to close the resource? Making `openStream` and `openChannel` return closeable resources is clearer with respect to the lifecycle of the returned resource. ---------------------------------------------------------------- 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] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
