flink-core/src/main/java/org/apache/flink/util/FileUtils.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.util;

import org.apache.flink.core.fs.FSDataInputStream;
import org.apache.flink.core.fs.FSDataOutputStream;
import org.apache.flink.core.fs.FileStatus;
import org.apache.flink.core.fs.FileSystem;
import org.apache.flink.core.fs.Path;
import org.apache.flink.util.function.ThrowingConsumer;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.SeekableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.AccessDeniedException;
import java.nio.file.Files;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.Random;

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

/**
 * This is a utility class to deal files and directories. Contains utilities for recursive
 * deletion and creation of temporary files.
 */
public final class FileUtils {

	/** Global lock to prevent concurrent directory deletes under Windows. */
	private static final Object WINDOWS_DELETE_LOCK = new Object();

	/** The alphabet to construct the random part of the filename from. */
	private static final char[] ALPHABET =
			{ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'a', 'b', 'c', 'd', 'e', 'f' };

	/** The length of the random part of the filename. */
	private static final int RANDOM_FILE_NAME_LENGTH = 12;

	/** The maximum size of array to allocate. More see {@link Files#MAX_BUFFER_SIZE}. */
	private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;

	// buffer size used for reading and writing
	private static final int BUFFER_SIZE = 8192;

	// ------------------------------------------------------------------------

	public static void writeCompletely(WritableByteChannel channel, ByteBuffer src) throws IOException {
		while (src.hasRemaining()) {
			channel.write(src);
		}
	}

	/**
	 * Constructs a random filename with the given prefix and
	 * a random part generated from hex characters.
	 *
	 * @param prefix
	 *        the prefix to the filename to be constructed
	 * @return the generated random filename with the given prefix
	 */
	public static String getRandomFilename(final String prefix) {
		final Random rnd = new Random();
		final StringBuilder stringBuilder = new StringBuilder(prefix);

		for (int i = 0; i < RANDOM_FILE_NAME_LENGTH; i++) {
			stringBuilder.append(ALPHABET[rnd.nextInt(ALPHABET.length)]);
		}

		return stringBuilder.toString();
	}

	// ------------------------------------------------------------------------
	//  Simple reading and writing of files
	// ------------------------------------------------------------------------

	public static String readFile(File file, String charsetName) throws IOException {
		byte[] bytes = Files.readAllBytes(file.toPath());
		return new String(bytes, charsetName);
	}

	public static String readFileUtf8(File file) throws IOException {
		return readFile(file, "UTF-8");
	}

	public static void writeFile(File file, String contents, String encoding) throws IOException {
		byte[] bytes = contents.getBytes(encoding);
		Files.write(file.toPath(), bytes, StandardOpenOption.WRITE);
	}

	public static void writeFileUtf8(File file, String contents) throws IOException {
		writeFile(file, contents, "UTF-8");
	}

	/**
	 * Reads all the bytes from a file. Uses {@code directBufferSize} to limit
	 * the size of the direct buffer used to read.
	 *
	 * @param path
	 *        the path to the file
	 * @param directBufferSize
	 *        the size of direct buffer used to read
	 * @return a byte array containing the bytes read from the file
	 * @throws IOException
	 *         if an I/O error occurs reading from the stream
	 */
	public static byte[] readAllBytes(java.nio.file.Path path, int directBufferSize) throws IOException {
		try (SeekableByteChannel channel = Files.newByteChannel(path);
			InputStream in = Channels.newInputStream(channel)) {
			long size = channel.size();
			if (size > (long) MAX_BUFFER_SIZE) {
				throw new OutOfMemoryError("Required array size too large");
			}

			return read(in, (int) size, directBufferSize);
		}
	}

	/**
	 * Reads all the bytes from an input stream. Uses {@code initialSize} as a hint
	 * about how many bytes the stream will have and uses {@code directBufferSize}
	 * to limit the size of the direct buffer used to read.
	 *
	 * @param source
	 *        the input stream to read from
	 * @param initialSize
	 *        the initial size of the byte array to allocate, use default {@link #BUFFER_SIZE}
	 *        if <= 0
	 * @param directBufferSize
	 * @return a byte array containing the bytes read from the file
	 * @throws IOException
	 *         if an I/O error occurs reading from the stream
	 */
	public static byte[] read(InputStream source, int initialSize, int directBufferSize) throws IOException {
		int capacity = initialSize;
		byte[] buf = new byte[capacity];
		int nread = 0;
		int n;
		directBufferSize = (directBufferSize <= 0) ? BUFFER_SIZE : directBufferSize;
		for (; ;) {
			// read to EOF which may read more or less than initialSize (eg: file
			// is truncated while we are reading)
			while ((n = source.read(buf, nread, Math.min(capacity - nread, directBufferSize))) > 0) {
				nread += n;
			}

			// if last call to source.read() returned -1, we are done
			// otherwise, try to read one more byte; if that failed we're done too
			if (n < 0 || (n = source.read()) < 0) {
				break;
			}

			// one more byte was read; need to allocate a larger buffer
			if (capacity <= MAX_BUFFER_SIZE - capacity) {
				capacity = Math.max(capacity << 1, BUFFER_SIZE);
			} else {
				if (capacity == MAX_BUFFER_SIZE) {
					throw new OutOfMemoryError("Required array size too large");
				}
				capacity = MAX_BUFFER_SIZE;
			}
			buf = Arrays.copyOf(buf, capacity);
			buf[nread++] = (byte) n;
		}
		return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
	}

	// ------------------------------------------------------------------------
	//  Deleting directories on standard File Systems
	// ------------------------------------------------------------------------

	/**
	 * Removes the given file or directory recursively.
	 *
	 * <p>If the file or directory does not exist, this does not throw an exception, but simply does nothing.
	 * It considers the fact that a file-to-be-deleted is not present a success.
	 *
	 * <p>This method is safe against other concurrent deletion attempts.
	 *
	 * @param file The file or directory to delete.
	 *
	 * @throws IOException Thrown if the directory could not be cleaned for some reason, for example
	 *                     due to missing access/write permissions.
	 */
	public static void deleteFileOrDirectory(File file) throws IOException {
		checkNotNull(file, "file");

		guardIfWindows(FileUtils::deleteFileOrDirectoryInternal, file);
	}

	/**
	 * Deletes the given directory recursively.
	 *
	 * <p>If the directory does not exist, this does not throw an exception, but simply does nothing.
	 * It considers the fact that a directory-to-be-deleted is not present a success.
	 *
	 * <p>This method is safe against other concurrent deletion attempts.
	 *
	 * @param directory The directory to be deleted.
	 * @throws IOException Thrown if the given file is not a directory, or if the directory could not be
	 *                     deleted for some reason, for example due to missing access/write permissions.
	 */
	public static void deleteDirectory(File directory) throws IOException {
		checkNotNull(directory, "directory");

		guardIfWindows(FileUtils::deleteDirectoryInternal, directory);
	}

	/**
	 * Deletes the given directory recursively, not reporting any I/O exceptions
	 * that occur.
	 *
	 * <p>This method is identical to {@link FileUtils#deleteDirectory(File)}, except that it
	 * swallows all exceptions and may leave the job quietly incomplete.
	 *
	 * @param directory The directory to delete.
	 */
	public static void deleteDirectoryQuietly(File directory) {
		if (directory == null) {
			return;
		}

		// delete and do not report if it fails
		try {
			deleteDirectory(directory);
		} catch (Exception ignored) {}
	}

	/**
	 * Removes all files contained within a directory, without removing the directory itself.
	 *
	 * <p>This method is safe against other concurrent deletion attempts.
	 *
	 * @param directory The directory to remove all files from.
	 *
	 * @throws FileNotFoundException Thrown if the directory itself does not exist.
	 * @throws IOException Thrown if the file indicates a proper file and not a directory, or if
	 *                     the directory could not be cleaned for some reason, for example
	 *                     due to missing access/write permissions.
	 */
	public static void cleanDirectory(File directory) throws IOException {
		checkNotNull(directory, "directory");

		guardIfWindows(FileUtils::cleanDirectoryInternal, directory);
	}

	private static void deleteFileOrDirectoryInternal(File file) throws IOException {
		if (file.isDirectory()) {
			// file exists and is directory
			deleteDirectoryInternal(file);
		}
		else {
			// if the file is already gone (concurrently), we don't mind
			Files.deleteIfExists(file.toPath());
		}
		// else: already deleted
	}

	private static void deleteDirectoryInternal(File directory) throws IOException {
		if (directory.isDirectory()) {
			// directory exists and is a directory

			// empty the directory first
			try {
				cleanDirectoryInternal(directory);
			}
			catch (FileNotFoundException ignored) {
				// someone concurrently deleted the directory, nothing to do for us
				return;
			}

			// delete the directory. this fails if the directory is not empty, meaning
			// if new files got concurrently created. we want to fail then.
			// if someone else deleted the empty directory concurrently, we don't mind
			// the result is the same for us, after all
			Files.deleteIfExists(directory.toPath());
		}
		else if (directory.exists()) {
			// exists but is file, not directory
			// either an error from the caller, or concurrently a file got created
			throw new IOException(directory + " is not a directory");
		}
		// else: does not exist, which is okay (as if deleted)
	}

	private static void cleanDirectoryInternal(File directory) throws IOException {
		if (directory.isDirectory()) {
			final File[] files = directory.listFiles();

			if (files == null) {
				// directory does not exist any more or no permissions
				if (directory.exists()) {
					throw new IOException("Failed to list contents of " + directory);
				} else {
					throw new FileNotFoundException(directory.toString());
				}
			}

			// remove all files in the directory
			for (File file : files) {
				if (file != null) {
					deleteFileOrDirectory(file);
				}
			}
		}
		else if (directory.exists()) {
			throw new IOException(directory + " is not a directory but a regular file");
		}
		else {
			// else does not exist at all
			throw new FileNotFoundException(directory.toString());
		}
	}

	private static void guardIfWindows(ThrowingConsumer<File, IOException> toRun, File file) throws IOException {
		if (!OperatingSystem.isWindows()) {
			toRun.accept(file);
		}
		else {
			// for windows, we synchronize on a global lock, to prevent concurrent delete issues
			// >
			// in the future, we may want to find either a good way of working around file visibility
			// in Windows under concurrent operations (the behavior seems completely unpredictable)
			// or  make this locking more fine grained, for example  on directory path prefixes
			synchronized (WINDOWS_DELETE_LOCK) {
				for (int attempt = 1; attempt <= 10; attempt++) {
					try {
						toRun.accept(file);
						break;
					}
					catch (AccessDeniedException e) {
						// ah, windows...
					}

					// briefly wait and fall through the loop
					try {
						Thread.sleep(1);
					} catch (InterruptedException e) {
						// restore the interruption flag and error out of the method
						Thread.currentThread().interrupt();
						throw new IOException("operation interrupted");
					}
				}
			}
		}
	}

	// ------------------------------------------------------------------------
	//  Deleting directories on Flink FileSystem abstraction
	// ------------------------------------------------------------------------

	/**
	 * Deletes the path if it is empty. A path can only be empty if it is a directory which does
	 * not contain any other directories/files.
	 *
	 * @param fileSystem to use
	 * @param path to be deleted if empty
	 * @return true if the path could be deleted; otherwise false
	 * @throws IOException if the delete operation fails
	 */
	public static boolean deletePathIfEmpty(FileSystem fileSystem, Path path) throws IOException {
		final FileStatus[] fileStatuses;

		try {
			fileStatuses = fileSystem.listStatus(path);
		}
		catch (FileNotFoundException e) {
			// path already deleted
			return true;
		}
		catch (Exception e) {
			// could not access directory, cannot delete
			return false;
		}

		// if there are no more files or if we couldn't list the file status try to delete the path
		if (fileStatuses == null) {
			// another indicator of "file not found"
			return true;
		}
		else if (fileStatuses.length == 0) {
			// attempt to delete the path (will fail and be ignored if the path now contains
			// some files (possibly added concurrently))
			return fileSystem.delete(path, false);
		}
		else {
			return false;
		}
	}

	/**
	 * Copies all files from source to target and sets executable flag. Paths might be on different systems.
	 * @param sourcePath source path to copy from
	 * @param targetPath target path to copy to
	 * @param executable if target file should be executable
	 * @throws IOException if the copy fails
	 */
	public static void copy(Path sourcePath, Path targetPath, boolean executable) throws IOException {
		// we unwrap the file system to get raw streams without safety net
		FileSystem sFS = FileSystem.getUnguardedFileSystem(sourcePath.toUri());
		FileSystem tFS = FileSystem.getUnguardedFileSystem(targetPath.toUri());
		if (!tFS.exists(targetPath)) {
			if (sFS.getFileStatus(sourcePath).isDir()) {
				tFS.mkdirs(targetPath);
				FileStatus[] contents = sFS.listStatus(sourcePath);
				for (FileStatus content : contents) {
					String distPath = content.getPath().toString();
					if (content.isDir()) {
						if (distPath.endsWith("/")) {
							distPath = distPath.substring(0, distPath.length() - 1);
						}
					}
					String localPath = targetPath.toString() + distPath.substring(distPath.lastIndexOf("/"));
					copy(content.getPath(), new Path(localPath), executable);
				}
			} else {
				try (FSDataOutputStream lfsOutput = tFS.create(targetPath, FileSystem.WriteMode.NO_OVERWRITE); FSDataInputStream fsInput = sFS.open(sourcePath)) {
					IOUtils.copyBytes(fsInput, lfsOutput);
					//noinspection ResultOfMethodCallIgnored
					new File(targetPath.toString()).setExecutable(executable);
				} catch (IOException ignored) {
				}
			}
		}
	}

	// ------------------------------------------------------------------------

	/**
	 * Private default constructor to avoid instantiation.
	 */
	private FileUtils() {}
}