org.apache.hadoop.hdfs.util.AtomicFileOutputStream Maven / Gradle / Ivy
/**
* 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.hadoop.hdfs.util;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.nativeio.NativeIO;
import org.apache.hadoop.io.nativeio.NativeIOException;
/**
* A FileOutputStream that has the property that it will only show
* up at its destination once it has been entirely written and flushed
* to disk. While being written, it will use a .tmp suffix.
*
* When the output stream is closed, it is flushed, fsynced, and
* will be moved into place, overwriting any file that already
* exists at that location.
*
* NOTE: on Windows platforms, it will not atomically
* replace the target file - instead the target file is deleted
* before this one is moved into place.
*/
public class AtomicFileOutputStream extends FilterOutputStream {
private static final String TMP_EXTENSION = ".tmp";
private final static Logger LOG = LoggerFactory.getLogger(
AtomicFileOutputStream.class);
private final File origFile;
private final File tmpFile;
public AtomicFileOutputStream(File f) throws FileNotFoundException {
// Code unfortunately must be duplicated below since we can't assign anything
// before calling super
super(new FileOutputStream(new File(f.getParentFile(), f.getName() + TMP_EXTENSION)));
origFile = f.getAbsoluteFile();
tmpFile = new File(f.getParentFile(), f.getName() + TMP_EXTENSION).getAbsoluteFile();
}
@Override
public void close() throws IOException {
boolean triedToClose = false, success = false;
try {
flush();
((FileOutputStream)out).getChannel().force(true);
triedToClose = true;
super.close();
success = true;
} finally {
if (success) {
boolean renamed = tmpFile.renameTo(origFile);
if (!renamed) {
// On windows, renameTo does not replace.
if (origFile.exists() && !origFile.delete()) {
throw new IOException("Could not delete original file " + origFile);
}
try {
NativeIO.renameTo(tmpFile, origFile);
} catch (NativeIOException e) {
throw new IOException("Could not rename temporary file " + tmpFile
+ " to " + origFile + " due to failure in native rename. "
+ e.toString());
}
}
} else {
if (!triedToClose) {
// If we failed when flushing, try to close it to not leak an FD
IOUtils.closeStream(out);
}
// close wasn't successful, try to delete the tmp file
if (!tmpFile.delete()) {
LOG.warn("Unable to delete tmp file " + tmpFile);
}
}
}
}
/**
* Close the atomic file, but do not "commit" the temporary file
* on top of the destination. This should be used if there is a failure
* in writing.
*/
public void abort() {
try {
super.close();
} catch (IOException ioe) {
LOG.warn("Unable to abort file " + tmpFile, ioe);
}
if (!tmpFile.delete()) {
LOG.warn("Unable to delete tmp file during abort " + tmpFile);
}
}
}