org.apache.lucene.store.SimpleFSLockFactory Maven / Gradle / Ivy
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/*
* COPIED FROM APACHE LUCENE 4.7.2
*
* Git URL: [email protected]:apache/lucene.git, tag: releases/lucene-solr/4.7.2, path: lucene/core/src/java
*
* (see https://issues.apache.org/jira/browse/OAK-10786 for details)
*/
package org.apache.lucene.store;
/*
* 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.
*/
import java.io.File;
import java.io.IOException;
/**
* Implements {@link LockFactory} using {@link
* File#createNewFile()}.
*
* NOTE: the {@linkplain File#createNewFile() javadocs
* for File.createNewFile()} contain a vague
* yet spooky warning about not using the API for file
* locking. This warning was added due to this
* bug, and in fact the only known problem with using
* this API for locking is that the Lucene write lock may
* not be released when the JVM exits abnormally.
* When this happens, a {@link LockObtainFailedException}
* is hit when trying to create a writer, in which case you
* need to explicitly clear the lock file first. You can
* either manually remove the file, or use the {@link
* org.apache.lucene.index.IndexWriter#unlock(Directory)}
* API. But, first be certain that no writer is in fact
* writing to the index otherwise you can easily corrupt
* your index.
*
* If you suspect that this or any other LockFactory is
* not working properly in your environment, you can easily
* test it by using {@link VerifyingLockFactory}, {@link
* LockVerifyServer} and {@link LockStressTest}.
*
* @see LockFactory
*/
public class SimpleFSLockFactory extends FSLockFactory {
/**
* Create a SimpleFSLockFactory instance, with null (unset)
* lock directory. When you pass this factory to a {@link FSDirectory}
* subclass, the lock directory is automatically set to the
* directory itself. Be sure to create one instance for each directory
* your create!
*/
public SimpleFSLockFactory() {
this((File) null);
}
/**
* Instantiate using the provided directory (as a File instance).
* @param lockDir where lock files should be created.
*/
public SimpleFSLockFactory(File lockDir) {
setLockDir(lockDir);
}
/**
* Instantiate using the provided directory name (String).
* @param lockDirName where lock files should be created.
*/
public SimpleFSLockFactory(String lockDirName) {
setLockDir(new File(lockDirName));
}
@Override
public Lock makeLock(String lockName) {
if (lockPrefix != null) {
lockName = lockPrefix + "-" + lockName;
}
return new SimpleFSLock(lockDir, lockName);
}
@Override
public void clearLock(String lockName) throws IOException {
if (lockDir.exists()) {
if (lockPrefix != null) {
lockName = lockPrefix + "-" + lockName;
}
File lockFile = new File(lockDir, lockName);
if (lockFile.exists() && !lockFile.delete()) {
throw new IOException("Cannot delete " + lockFile);
}
}
}
}
class SimpleFSLock extends Lock {
File lockFile;
File lockDir;
public SimpleFSLock(File lockDir, String lockFileName) {
this.lockDir = lockDir;
lockFile = new File(lockDir, lockFileName);
}
@Override
public boolean obtain() throws IOException {
// Ensure that lockDir exists and is a directory:
if (!lockDir.exists()) {
if (!lockDir.mkdirs())
throw new IOException("Cannot create directory: " +
lockDir.getAbsolutePath());
} else if (!lockDir.isDirectory()) {
// TODO: NoSuchDirectoryException instead?
throw new IOException("Found regular file where directory expected: " +
lockDir.getAbsolutePath());
}
return lockFile.createNewFile();
}
@Override
public void close() throws LockReleaseFailedException {
if (lockFile.exists() && !lockFile.delete()) {
throw new LockReleaseFailedException("failed to delete " + lockFile);
}
}
@Override
public boolean isLocked() {
return lockFile.exists();
}
@Override
public String toString() {
return "SimpleFSLock@" + lockFile;
}
}