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AtomicFileWriter.java
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AtomicFileWriter.java
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/*
* The MIT License
*
* Copyright (c) 2004-2009, Sun Microsystems, Inc., Kohsuke Kawaguchi
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package hudson.util;
import edu.umd.cs.findbugs.annotations.NonNull;
import edu.umd.cs.findbugs.annotations.Nullable;
import hudson.Functions;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.lang.ref.Cleaner;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.AtomicMoveNotSupportedException;
import java.nio.file.Files;
import java.nio.file.InvalidPathException;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.nio.file.StandardOpenOption;
import java.util.logging.Level;
import java.util.logging.Logger;
import jenkins.util.SystemProperties;
/**
* Buffered {@link FileWriter} that supports atomic operations.
*
* <p>
* The write operation is atomic when used for overwriting;
* it either leaves the original file intact, or it completely rewrites it with new contents.
*
* @author Kohsuke Kawaguchi
*/
public class AtomicFileWriter extends Writer {
private static final Logger LOGGER = Logger.getLogger(AtomicFileWriter.class.getName());
private static final Cleaner CLEANER = Cleaner.create(
new NamingThreadFactory(new DaemonThreadFactory(), AtomicFileWriter.class.getName() + ".cleaner"));
private static /* final */ boolean DISABLE_FORCED_FLUSH = SystemProperties.getBoolean(
AtomicFileWriter.class.getName() + ".DISABLE_FORCED_FLUSH");
private static /* final */ boolean REQUIRES_DIR_FSYNC = SystemProperties.getBoolean(
AtomicFileWriter.class.getName() + ".REQUIRES_DIR_FSYNC", !Functions.isWindows());
static {
if (DISABLE_FORCED_FLUSH) {
LOGGER.log(Level.WARNING, "DISABLE_FORCED_FLUSH flag used, this could result in dataloss if failures happen in your storage subsystem.");
}
}
private final FileChannelWriter core;
private final Path tmpPath;
private final Path destPath;
/**
* Writes with UTF-8 encoding.
*/
public AtomicFileWriter(File f) throws IOException {
this(toPath(f), StandardCharsets.UTF_8);
}
/**
* @param encoding File encoding to write. If null, platform default encoding is chosen.
*
* @deprecated Use {@link #AtomicFileWriter(Path, Charset)}
*/
@Deprecated
public AtomicFileWriter(@NonNull File f, @Nullable String encoding) throws IOException {
this(toPath(f), encoding == null ? Charset.defaultCharset() : Charset.forName(encoding));
}
/**
* Wraps potential {@link java.nio.file.InvalidPathException} thrown by {@link File#toPath()} in an
* {@link IOException} for backward compatibility.
*
* @param file file to obtain the path of
* @return the path for that file
* @see File#toPath()
*/
private static Path toPath(@NonNull File file) throws IOException {
try {
return file.toPath();
} catch (InvalidPathException e) {
throw new IOException(e);
}
}
/**
* @param destinationPath the destination path where to write the content when committed.
* @param charset File charset to write.
*/
public AtomicFileWriter(@NonNull Path destinationPath, @NonNull Charset charset) throws IOException {
// See FileChannelWriter docs to understand why we do not cause a force() call on flush() from AtomicFileWriter.
this(destinationPath, charset, false, true);
}
/**
* <strong>DO NOT USE THIS METHOD, OR YOU WILL LOSE DATA INTEGRITY.</strong>
*
* @param destinationPath the destination path where to write the content when committed.
* @param charset File charset to write.
* @param integrityOnFlush do not force writing to disk when flushing
* @param integrityOnClose do not force writing to disk when closing
* @deprecated use {@link AtomicFileWriter#AtomicFileWriter(Path, Charset)}
*/
@Deprecated
public AtomicFileWriter(@NonNull Path destinationPath, @NonNull Charset charset, boolean integrityOnFlush, boolean integrityOnClose) throws IOException {
if (charset == null) { // be extra-defensive if people don't care
throw new IllegalArgumentException("charset is null");
}
this.destPath = destinationPath;
Path dir = this.destPath.getParent();
if (Files.exists(dir) && !Files.isDirectory(dir)) {
throw new IOException(dir + " exists and is neither a directory nor a symlink to a directory");
}
else {
if (Files.isSymbolicLink(dir)) {
LOGGER.log(Level.CONFIG, "{0} is a symlink to a directory", dir);
} else {
Files.createDirectories(dir); // Cannot be called on symlink, so we are pretty defensive...
}
}
try {
// JENKINS-48407: NIO's createTempFile creates file with 0600 permissions, so we use pre-NIO for this...
tmpPath = File.createTempFile("atomic", "tmp", dir.toFile()).toPath();
} catch (IOException e) {
throw new IOException("Failed to create a temporary file in " + dir, e);
}
if (DISABLE_FORCED_FLUSH) {
integrityOnFlush = false;
integrityOnClose = false;
}
core = new FileChannelWriter(tmpPath, charset, integrityOnFlush, integrityOnClose, StandardOpenOption.WRITE, StandardOpenOption.CREATE);
CLEANER.register(this, new CleanupChecker(core, tmpPath, destPath));
}
@Override
public void write(int c) throws IOException {
core.write(c);
}
@Override
public void write(String str, int off, int len) throws IOException {
core.write(str, off, len);
}
@Override
public void write(char[] cbuf, int off, int len) throws IOException {
core.write(cbuf, off, len);
}
@Override
public void flush() throws IOException {
core.flush();
}
@Override
public void close() throws IOException {
core.close();
}
/**
* When the write operation failed, call this method to
* leave the original file intact and remove the temporary file.
* This method can be safely invoked from the "finally" block, even after
* the {@link #commit()} is called, to simplify coding.
*/
public void abort() throws IOException {
// One way or another, the temporary file should be deleted.
try {
close();
} finally {
Files.deleteIfExists(tmpPath);
}
}
public void commit() throws IOException {
close();
try {
// Try to make an atomic move.
Files.move(tmpPath, destPath, StandardCopyOption.ATOMIC_MOVE);
} catch (IOException moveFailed) {
// If it falls here that can mean many things. Either that the atomic move is not supported,
// or something wrong happened. Anyway, let's try to be over-diagnosing
if (moveFailed instanceof AtomicMoveNotSupportedException) {
LOGGER.log(Level.WARNING, "Atomic move not supported. falling back to non-atomic move.", moveFailed);
} else {
LOGGER.log(Level.WARNING, "Unable to move atomically, falling back to non-atomic move.", moveFailed);
}
if (destPath.toFile().exists()) {
LOGGER.log(Level.INFO, "The target file {0} was already existing", destPath);
}
try {
Files.move(tmpPath, destPath, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException replaceFailed) {
replaceFailed.addSuppressed(moveFailed);
LOGGER.log(Level.WARNING, "Unable to move {0} to {1}. Attempting to delete {0} and abandoning.",
new Path[]{tmpPath, destPath});
try {
Files.deleteIfExists(tmpPath);
} catch (IOException deleteFailed) {
replaceFailed.addSuppressed(deleteFailed);
LOGGER.log(Level.WARNING, "Unable to delete {0}, good bye then!", tmpPath);
throw replaceFailed;
}
throw replaceFailed;
}
}
/*
* From fsync(2) on Linux:
*
* Calling fsync() does not necessarily ensure that the entry in the directory containing the file has also
* reached disk. For that an explicit fsync() on a file descriptor for the directory is also needed.
*/
if (!DISABLE_FORCED_FLUSH && REQUIRES_DIR_FSYNC) {
try (FileChannel parentChannel = FileChannel.open(destPath.getParent())) {
parentChannel.force(true);
}
}
}
private static final class CleanupChecker implements Runnable {
private final FileChannelWriter core;
private final Path tmpPath;
private final Path destPath;
CleanupChecker(final FileChannelWriter core, final Path tmpPath, final Path destPath) {
this.core = core;
this.tmpPath = tmpPath;
this.destPath = destPath;
}
@Override
public void run() {
if (core.isOpen()) {
LOGGER.log(Level.WARNING, "AtomicFileWriter for " + destPath + " was not closed before being released");
try {
core.close();
} catch (IOException e) {
LOGGER.log(Level.WARNING, "Failed to close " + tmpPath + " for destination file " + destPath, e);
}
}
try {
Files.deleteIfExists(tmpPath);
} catch (IOException e) {
LOGGER.log(Level.WARNING, "Failed to delete temporary file " + tmpPath + " for destination file " + destPath, e);
}
}
}
/**
* Until the data is committed, this file captures
* the written content.
*
* @deprecated Use getTemporaryPath()
*/
@Deprecated
public File getTemporaryFile() {
return tmpPath.toFile();
}
/**
* Until the data is committed, this file captures
* the written content.
* @since 2.93
*/
public Path getTemporaryPath() {
return tmpPath;
}
}