flink-filesystems/flink-s3-fs-base/src/main/java/org/apache/flink/fs/s3/common/utils/RefCountedBufferingFileStream.java

/*
 * 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.s3.common.utils;

import org.apache.flink.annotation.Internal;
import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.util.function.FunctionWithException;

import java.io.File;
import java.io.IOException;

import static org.apache.flink.util.Preconditions.checkArgument;
import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * A {@link RefCountedFile} that also uses an in-memory buffer for buffering small writes.
 * This is done to avoid frequent 'flushes' of the file stream to disk.
 */
@Internal
public class RefCountedBufferingFileStream extends RefCountedFSOutputStream {

	public static final int BUFFER_SIZE = 4096;

	private final RefCountedFile currentTmpFile;

	/** The write buffer. */
	private final byte[] buffer;

	/** Current position in the buffer, must be in [0, buffer.length]. */
	private int positionInBuffer;

	private boolean closed;

	@VisibleForTesting
	public RefCountedBufferingFileStream(
			final RefCountedFile file,
			final int bufferSize) {

		checkArgument(bufferSize > 0L);

		this.currentTmpFile = checkNotNull(file);
		this.buffer = new byte[bufferSize];
		this.positionInBuffer = 0;
		this.closed = false;
	}

	@Override
	public File getInputFile() {
		return currentTmpFile.getFile();
	}

	@Override
	public long getPos() {
		return currentTmpFile.getLength() + positionInBuffer;
	}

	@Override
	public void write(int b) throws IOException {
		if (positionInBuffer >= buffer.length) {
			flush();
		}

		requireOpen();

		buffer[positionInBuffer++] = (byte) b;
	}

	@Override
	public void write(byte[] b, int off, int len) throws IOException {
		if (len >= buffer.length) {
			// circumvent the internal buffer for large writes
			flush();
			currentTmpFile.write(b, off, len);
			return;
		}

		requireOpen();

		if (len > buffer.length - positionInBuffer) {
			flush();
		}

		System.arraycopy(b, off, buffer, positionInBuffer, len);
		positionInBuffer += len;
	}

	@Override
	public void flush() throws IOException {
		currentTmpFile.write(buffer, 0, positionInBuffer);
		currentTmpFile.flush();
		positionInBuffer = 0;
	}

	@Override
	public void sync() throws IOException {
		throw new UnsupportedOperationException("S3RecoverableFsDataOutputStream cannot sync state to S3. " +
				"Use persist() to create a persistent recoverable intermediate point.");
	}

	@Override
	public boolean isClosed() throws IOException {
		return closed;
	}

	@Override
	public void close() {
		if (!closed) {
			currentTmpFile.closeStream();
			closed = true;
		}
	}

	@Override
	public void retain() {
		currentTmpFile.retain();
	}

	@Override
	public boolean release() {
		return currentTmpFile.release();
	}

	private void requireOpen() throws IOException {
		if (closed) {
			throw new IOException("Stream closed.");
		}
	}

	@Override
	public String toString() {
		return "Reference Counted File with {" +
				"path=\'" + currentTmpFile.getFile().toPath().toAbsolutePath() + "\'" +
				", size=" + getPos() +
				", reference counter=" + currentTmpFile.getReferenceCounter() +
				", closed=" + closed +
				'}';
	}

	@VisibleForTesting
	int getPositionInBuffer() {
		return positionInBuffer;
	}

	@VisibleForTesting
	public int getReferenceCounter() {
		return currentTmpFile.getReferenceCounter();
	}

	// ------------------------- Factory Methods -------------------------

	public static RefCountedBufferingFileStream openNew(
			final FunctionWithException<File, RefCountedFile, IOException> tmpFileProvider) throws IOException {

		return new RefCountedBufferingFileStream(
				tmpFileProvider.apply(null),
				BUFFER_SIZE);
	}

	public static RefCountedBufferingFileStream restore(
			final FunctionWithException<File, RefCountedFile, IOException> tmpFileProvider,
			final File initialTmpFile) throws IOException {

		return new RefCountedBufferingFileStream(
				tmpFileProvider.apply(initialTmpFile),
				BUFFER_SIZE);
	}
}