Samrat002 commented on code in PR #27187: URL: https://github.com/apache/flink/pull/27187#discussion_r2935123320
########## flink-filesystems/flink-s3-fs-native/src/main/java/org/apache/flink/fs/s3native/writer/NativeS3RecoverableFsDataOutputStream.java: ########## @@ -0,0 +1,291 @@ +/* + * 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.writer; + +import org.apache.flink.core.fs.RecoverableFsDataOutputStream; +import org.apache.flink.core.fs.RecoverableWriter; +import org.apache.flink.fs.s3native.writer.NativeS3Recoverable.PartETag; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.concurrent.NotThreadSafe; + +import java.io.BufferedOutputStream; +import java.io.File; +import java.io.FileOutputStream; +import java.io.IOException; +import java.nio.file.Files; +import java.util.ArrayList; +import java.util.List; +import java.util.UUID; +import java.util.concurrent.locks.ReentrantLock; + +/** + * A recoverable output stream writes data to S3 using multipart uploads. + * + * <p>This class is NOT thread-safe. All write operations ({@link #write}, {@link #flush}, {@link + * #persist}, {@link #closeForCommit}) must be called from a single thread (the Flink operator + * thread). This is consistent with Flink's {@link RecoverableFsDataOutputStream} contract where + * output streams are confined to a single task thread. + * + * <p>The {@link #close()} method may be called concurrently (e.g., during task cancellation). A + * {@link ReentrantLock} guards the critical sections in {@link #close()}, {@link + * #closeForCommit()}, and {@link #persist()} to ensure safe cleanup of local resources without + * corrupting S3 state. + */ +@NotThreadSafe +public class NativeS3RecoverableFsDataOutputStream extends RecoverableFsDataOutputStream { + + private static final Logger LOG = + LoggerFactory.getLogger(NativeS3RecoverableFsDataOutputStream.class); + + private static final int BUFFER_SIZE = 64 * 1024; + private final ReentrantLock lock = new ReentrantLock(); + + private final NativeS3AccessHelper s3AccessHelper; + private final String key; + private final String uploadId; + private final String localTmpDir; + private final long minPartSize; + + private final List<PartETag> completedParts; + private long numBytesInParts; + + private File currentTempFile; + private FileOutputStream currentFileStream; + private BufferedOutputStream currentOutputStream; + private long currentPartSize; + private int nextPartNumber; + + private volatile boolean closed; + + public NativeS3RecoverableFsDataOutputStream( + NativeS3AccessHelper s3AccessHelper, + String key, + String uploadId, + String localTmpDir, + long minPartSize) + throws IOException { + this(s3AccessHelper, key, uploadId, localTmpDir, minPartSize, new ArrayList<>(), 0L); + } + + public NativeS3RecoverableFsDataOutputStream( + NativeS3AccessHelper s3AccessHelper, + String key, + String uploadId, + String localTmpDir, + long minPartSize, + List<PartETag> existingParts, + long numBytesInParts) + throws IOException { + this.s3AccessHelper = s3AccessHelper; + this.key = key; + this.uploadId = uploadId; + this.localTmpDir = localTmpDir; + this.minPartSize = minPartSize; + this.completedParts = new ArrayList<>(existingParts); + this.numBytesInParts = numBytesInParts; + this.nextPartNumber = existingParts.size() + 1; + this.currentPartSize = 0; + this.closed = false; + + createNewTempFile(); + } + + private void createNewTempFile() throws IOException { + File tmpDir = new File(localTmpDir); + if (!tmpDir.exists()) { + tmpDir.mkdirs(); + } + + currentTempFile = new File(tmpDir, "s3-part-" + UUID.randomUUID()); + currentFileStream = new FileOutputStream(currentTempFile); + currentOutputStream = new BufferedOutputStream(currentFileStream, BUFFER_SIZE); + currentPartSize = 0; + } + + @Override + public long getPos() throws IOException { + return numBytesInParts + currentPartSize; + } + + @Override + public void write(int b) throws IOException { + if (closed) { + throw new IOException("Stream is closed"); + } + + currentOutputStream.write(b); + currentPartSize++; + + if (currentPartSize >= minPartSize) { + uploadCurrentPart(); + createNewTempFile(); + } + } Review Comment: Line 43-46 explains ``` * <p>This class is NOT thread-safe. All write operations ({@link #write}, {@link #flush}, {@link * #persist}, {@link #closeForCommit}) must be called from a single thread (the Flink operator * thread). This is consistent with Flink's {@link RecoverableFsDataOutputStream} contract where * output streams are confined to a single task thread. ``` > This seems to be a common problem in this and other classes. This isn't a common problem in other classes. It's a deliberate trade-off specific to this recoverable writer pattern. The Javadoc contract is the safety guarantee. If you think the design intent should be more explicit in the code, I can add a clarifying comment. -- 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]
