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.FilenameFilter;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.concurrent.Future; // javadoc
import org.apache.lucene.util.ThreadInterruptedException;
import org.apache.lucene.util.Constants;
/**
* <a name="subclasses"/>
* Base class for Directory implementations that store index
* files in the file system. There are currently three core
* subclasses:
*
* <ul>
*
* <li> {@link SimpleFSDirectory} is a straightforward
* implementation using java.io.RandomAccessFile.
* However, it has poor concurrent performance
* (multiple threads will bottleneck) as it
* synchronizes when multiple threads read from the
* same file.
*
* <li> {@link NIOFSDirectory} uses java.nio's
* FileChannel's positional io when reading to avoid
* synchronization when reading from the same file.
* Unfortunately, due to a Windows-only <a
* href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6265734">Sun
* JRE bug</a> this is a poor choice for Windows, but
* on all other platforms this is the preferred
* choice. Applications using {@link Thread#interrupt()} or
* {@link Future#cancel(boolean)} should use
* {@link SimpleFSDirectory} instead. See {@link NIOFSDirectory} java doc
* for details.
*
*
*
* <li> {@link MMapDirectory} uses memory-mapped IO when
* reading. This is a good choice if you have plenty
* of virtual memory relative to your index size, eg
* if you are running on a 64 bit JRE, or you are
* running on a 32 bit JRE but your index sizes are
* small enough to fit into the virtual memory space.
* Java has currently the limitation of not being able to
* unmap files from user code. The files are unmapped, when GC
* releases the byte buffers. Due to
* <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4724038">
* this bug</a> in Sun's JRE, MMapDirectory's {@link IndexInput#close}
* is unable to close the underlying OS file handle. Only when
* GC finally collects the underlying objects, which could be
* quite some time later, will the file handle be closed.
* This will consume additional transient disk usage: on Windows,
* attempts to delete or overwrite the files will result in an
* exception; on other platforms, which typically have a "delete on
* last close" semantics, while such operations will succeed, the bytes
* are still consuming space on disk. For many applications this
* limitation is not a problem (e.g. if you have plenty of disk space,
* and you don't rely on overwriting files on Windows) but it's still
* an important limitation to be aware of. This class supplies a
* (possibly dangerous) workaround mentioned in the bug report,
* which may fail on non-Sun JVMs.
*
* Applications using {@link Thread#interrupt()} or
* {@link Future#cancel(boolean)} should use
* {@link SimpleFSDirectory} instead. See {@link MMapDirectory}
* java doc for details.
* </ul>
*
* Unfortunately, because of system peculiarities, there is
* no single overall best implementation. Therefore, we've
* added the {@link #open} method, to allow Lucene to choose
* the best FSDirectory implementation given your
* environment, and the known limitations of each
* implementation. For users who have no reason to prefer a
* specific implementation, it's best to simply use {@link
* #open}. For all others, you should instantiate the
* desired implementation directly.
*
* <p>The locking implementation is by default {@link
* NativeFSLockFactory}, but can be changed by
* passing in a custom {@link LockFactory} instance.
*
* @see Directory
*/
public abstract class FSDirectory extends Directory {
private static MessageDigest DIGESTER;
static {
try {
DIGESTER = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e.toString(), e);
}
}
// returns the canonical version of the directory, creating it if it doesn't exist.
private static File getCanonicalPath(File file) throws IOException {
return new File(file.getCanonicalPath());
}
private boolean checked;
final void createDir() throws IOException {
if (!checked) {
if (!directory.exists())
if (!directory.mkdirs())
throw new IOException("Cannot create directory: " + directory);
checked = true;
}
}
/** Initializes the directory to create a new file with the given name.
* This method should be used in {@link #createOutput}. */
protected final void initOutput(String name) throws IOException {
ensureOpen();
createDir();
File file = new File(directory, name);
if (file.exists() && !file.delete()) // delete existing, if any
throw new IOException("Cannot overwrite: " + file);
}
/** The underlying filesystem directory */
protected File directory = null;
/** Create a new FSDirectory for the named location (ctor for subclasses).
* @param path the path of the directory
* @param lockFactory the lock factory to use, or null for the default
* ({@link NativeFSLockFactory});
* @throws IOException
*/
protected FSDirectory(File path, LockFactory lockFactory) throws IOException {
path = getCanonicalPath(path);
// new ctors use always NativeFSLockFactory as default:
if (lockFactory == null) {
lockFactory = new NativeFSLockFactory();
}
directory = path;
if (directory.exists() && !directory.isDirectory())
throw new NoSuchDirectoryException("file '" + directory + "' exists but is not a directory");
setLockFactory(lockFactory);
// for filesystem based LockFactory, delete the lockPrefix, if the locks are placed
// in index dir. If no index dir is given, set ourselves
if (lockFactory instanceof FSLockFactory) {
final FSLockFactory lf = (FSLockFactory) lockFactory;
final File dir = lf.getLockDir();
// if the lock factory has no lockDir set, use the this directory as lockDir
if (dir == null) {
lf.setLockDir(this.directory);
lf.setLockPrefix(null);
} else if (dir.getCanonicalPath().equals(this.directory.getCanonicalPath())) {
lf.setLockPrefix(null);
}
}
}
/** Creates an FSDirectory instance, trying to pick the
* best implementation given the current environment.
* The directory returned uses the {@link NativeFSLockFactory}.
*
* <p>Currently this returns {@link NIOFSDirectory}
* on non-Windows JREs and {@link SimpleFSDirectory}
* on Windows. It is highly recommended that you consult the
* implementation's documentation for your platform before
* using this method.
*
* <p><b>NOTE</b>: this method may suddenly change which
* implementation is returned from release to release, in
* the event that higher performance defaults become
* possible; if the precise implementation is important to
* your application, please instantiate it directly,
* instead. On 64 bit systems, it may also good to
* return {@link MMapDirectory}, but this is disabled
* because of officially missing unmap support in Java.
* For optimal performance you should consider using
* this implementation on 64 bit JVMs.
*
* <p>See <a href="#subclasses">above</a> */
public static FSDirectory open(File path) throws IOException {
return open(path, null);
}
/** Just like {@link #open(File)}, but allows you to
* also specify a custom {@link LockFactory}. */
public static FSDirectory open(File path, LockFactory lockFactory) throws IOException {
/* For testing:
MMapDirectory dir=new MMapDirectory(path, lockFactory);
dir.setUseUnmap(true);
return dir;
*/
if (Constants.WINDOWS) {
return new SimpleFSDirectory(path, lockFactory);
} else {
return new NIOFSDirectory(path, lockFactory);
}
}
/** Lists all files (not subdirectories) in the
* directory. This method never returns null (throws
* {@link IOException} instead).
*
* @throws NoSuchDirectoryException if the directory
* does not exist, or does exist but is not a
* directory.
* @throws IOException if list() returns null */
public static String[] listAll(File dir) throws IOException {
if (!dir.exists())
throw new NoSuchDirectoryException("directory '" + dir + "' does not exist");
else if (!dir.isDirectory())
throw new NoSuchDirectoryException("file '" + dir + "' exists but is not a directory");
// Exclude subdirs
String[] result = dir.list(new FilenameFilter() {
public boolean accept(File dir, String file) {
return !new File(dir, file).isDirectory();
}
});
if (result == null)
throw new IOException("directory '" + dir + "' exists and is a directory, but cannot be listed: list() returned null");
return result;
}
/** Lists all files (not subdirectories) in the
* directory.
* @see #listAll(File) */
@Override
public String[] listAll() throws IOException {
ensureOpen();
return listAll(directory);
}
/** Returns true iff a file with the given name exists. */
@Override
public boolean fileExists(String name) {
ensureOpen();
File file = new File(directory, name);
return file.exists();
}
/** Returns the time the named file was last modified. */
@Override
public long fileModified(String name) {
ensureOpen();
File file = new File(directory, name);
return file.lastModified();
}
/** Returns the time the named file was last modified. */
public static long fileModified(File directory, String name) {
File file = new File(directory, name);
return file.lastModified();
}
/** Set the modified time of an existing file to now. */
@Override
public void touchFile(String name) {
ensureOpen();
File file = new File(directory, name);
file.setLastModified(System.currentTimeMillis());
}
/** Returns the length in bytes of a file in the directory. */
@Override
public long fileLength(String name) {
ensureOpen();
File file = new File(directory, name);
return file.length();
}
/** Removes an existing file in the directory. */
@Override
public void deleteFile(String name) throws IOException {
ensureOpen();
File file = new File(directory, name);
if (!file.delete())
throw new IOException("Cannot delete " + file);
}
@Override
public void sync(String name) throws IOException {
ensureOpen();
File fullFile = new File(directory, name);
boolean success = false;
int retryCount = 0;
IOException exc = null;
while(!success && retryCount < 5) {
retryCount++;
RandomAccessFile file = null;
try {
try {
file = new RandomAccessFile(fullFile, "rw");
file.getFD().sync();
success = true;
} finally {
if (file != null)
file.close();
}
} catch (IOException ioe) {
if (exc == null)
exc = ioe;
try {
// Pause 5 msec
Thread.sleep(5);
} catch (InterruptedException ie) {
throw new ThreadInterruptedException(ie);
}
}
}
if (!success)
// Throw original exception
throw exc;
}
// Inherit javadoc
@Override
public IndexInput openInput(String name) throws IOException {
ensureOpen();
return openInput(name, BufferedIndexInput.BUFFER_SIZE);
}
/**
* So we can do some byte-to-hexchar conversion below
*/
private static final char[] HEX_DIGITS =
{'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
@Override
public String getLockID() {
ensureOpen();
String dirName; // name to be hashed
try {
dirName = directory.getCanonicalPath();
} catch (IOException e) {
throw new RuntimeException(e.toString(), e);
}
byte digest[];
synchronized (DIGESTER) {
digest = DIGESTER.digest(dirName.getBytes());
}
StringBuilder buf = new StringBuilder();
buf.append("lucene-");
for (int i = 0; i < digest.length; i++) {
int b = digest[i];
buf.append(HEX_DIGITS[(b >> 4) & 0xf]);
buf.append(HEX_DIGITS[b & 0xf]);
}
return buf.toString();
}
/** Closes the store to future operations. */
@Override
public synchronized void close() {
isOpen = false;
}
public File getFile() {
ensureOpen();
return directory;
}
/** For debug output. */
@Override
public String toString() {
return this.getClass().getName() + "@" + directory + " lockFactory=" + getLockFactory();
}
/**
* Default read chunk size. This is a conditional
* default: on 32bit JVMs, it defaults to 100 MB. On
* 64bit JVMs, it's <code>Integer.MAX_VALUE</code>.
* @see #setReadChunkSize
*/
public static final int DEFAULT_READ_CHUNK_SIZE = Constants.JRE_IS_64BIT ? Integer.MAX_VALUE: 100 * 1024 * 1024;
// LUCENE-1566
private int chunkSize = DEFAULT_READ_CHUNK_SIZE;
/**
* Sets the maximum number of bytes read at once from the
* underlying file during {@link IndexInput#readBytes}.
* The default value is {@link #DEFAULT_READ_CHUNK_SIZE};
*
* <p> This was introduced due to <a
* href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6478546">Sun
* JVM Bug 6478546</a>, which throws an incorrect
* OutOfMemoryError when attempting to read too many bytes
* at once. It only happens on 32bit JVMs with a large
* maximum heap size.</p>
*
* <p>Changes to this value will not impact any
* already-opened {@link IndexInput}s. You should call
* this before attempting to open an index on the
* directory.</p>
*
* <p> <b>NOTE</b>: This value should be as large as
* possible to reduce any possible performance impact. If
* you still encounter an incorrect OutOfMemoryError,
* trying lowering the chunk size.</p>
*/
public final void setReadChunkSize(int chunkSize) {
// LUCENE-1566
if (chunkSize <= 0) {
throw new IllegalArgumentException("chunkSize must be positive");
}
if (!Constants.JRE_IS_64BIT) {
this.chunkSize = chunkSize;
}
}
/**
* The maximum number of bytes to read at once from the
* underlying file during {@link IndexInput#readBytes}.
* @see #setReadChunkSize
*/
public final int getReadChunkSize() {
// LUCENE-1566
return chunkSize;
}
}