Izeren commented on code in PR #27187: URL: https://github.com/apache/flink/pull/27187#discussion_r2812753476
########## flink-filesystems/flink-s3-fs-native/src/main/java/org/apache/flink/fs/s3native/NativeS3BulkCopyHelper.java: ########## @@ -0,0 +1,199 @@ +/* + * 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.flink.fs.s3native; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.core.fs.ICloseableRegistry; +import org.apache.flink.core.fs.PathsCopyingFileSystem; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import software.amazon.awssdk.transfer.s3.S3TransferManager; +import software.amazon.awssdk.transfer.s3.model.CompletedCopy; +import software.amazon.awssdk.transfer.s3.model.DownloadFileRequest; +import software.amazon.awssdk.transfer.s3.model.FileDownload; + +import java.io.File; +import java.io.IOException; +import java.nio.file.Files; +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.ExecutionException; + +/** + * Helper class for performing bulk S3 to local file system copies using S3TransferManager. + * + * <p><b>Concurrency Model:</b> Uses batch-based concurrency control with {@code + * maxConcurrentCopies} to limit parallel downloads. The current implementation waits for each batch + * to complete before starting the next batch. A future enhancement could use a bounded thread pool + * (e.g., {@link java.util.concurrent.Semaphore} or bounded executor) to allow continuous submission + * of new downloads as slots become available, which would provide better throughput by avoiding the + * "slowest task in batch" bottleneck. + * + * <p><b>Retry Handling:</b> Relies on the S3TransferManager's built-in retry mechanism for + * transient failures. If a download fails after retries: + * + * <ul> + * <li>The entire bulk copy operation fails with an IOException + * <li>Successfully downloaded files are NOT cleaned up (they remain on disk) + * <li>Partial downloads may leave incomplete files that should be cleaned up by the caller + * </ul> + * + * <p><b>Cleanup:</b> No automatic cleanup is performed on failure. Callers are responsible for + * cleaning up destination files if the bulk copy fails. Consider wrapping in a try-finally or using + * a temp directory that can be deleted on failure. + * + * <p><b>TODO:</b> Consider extracting URI parsing logic to a shared S3UriUtils utility class to + * consolidate S3 URI handling across the codebase. + */ +@Internal +public class NativeS3BulkCopyHelper { + + private static final Logger LOG = LoggerFactory.getLogger(NativeS3BulkCopyHelper.class); + + private final S3TransferManager transferManager; + private final int maxConcurrentCopies; + + public NativeS3BulkCopyHelper(S3TransferManager transferManager, int maxConcurrentCopies) { + this.transferManager = transferManager; + this.maxConcurrentCopies = maxConcurrentCopies; + } + + /** + * Copies files from S3 to local filesystem in batches. + * + * @param requests List of copy requests (source S3 path to destination local path) + * @param closeableRegistry Registry for cleanup (currently unused, reserved for future use) + * @throws IOException if any copy operation fails + */ + public void copyFiles( + List<PathsCopyingFileSystem.CopyRequest> requests, ICloseableRegistry closeableRegistry) + throws IOException { + + if (requests.isEmpty()) { + return; + } + + LOG.info("Starting bulk copy of {} files using S3TransferManager", requests.size()); + + List<CompletableFuture<CompletedCopy>> copyFutures = new ArrayList<>(); + + for (int i = 0; i < requests.size(); i++) { + PathsCopyingFileSystem.CopyRequest request = requests.get(i); + String sourceUri = request.getSource().toUri().toString(); + if (sourceUri.startsWith("s3://") || sourceUri.startsWith("s3a://")) { + CompletableFuture<CompletedCopy> future = copyS3ToLocal(request); Review Comment: !nit, ``` CompletableFuture<CompletedCopy> future = copyS3ToLocal(request); copyFutures.add(future); ``` could be inlined -- This is an automated message from the Apache Git Service. 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