| /** |
| * 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.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.hadoop.io.IOUtils; |
| |
| /** |
| * 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. |
| * |
| * <b>NOTE</b>: 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 Log LOG = LogFactory.getLog( |
| 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.delete() || !tmpFile.renameTo(origFile)) { |
| throw new IOException("Could not rename temporary file " + |
| tmpFile + " to " + origFile); |
| } |
| } |
| } 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); |
| } |
| } |
| } |
| } |
| |
| } |