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 org.apache.lucene.util.Constants;
import org.apache.lucene.util.IOUtils;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.Future;
import static java.util.Collections.synchronizedSet;
/**
* Base class for Directory implementations that store index
* files in the file system.
* <a name="subclasses"/>
* 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 BaseDirectory {
/**
* Default read chunk size: 8192 bytes (this is the size up to which the JDK
does not allocate additional arrays while reading/writing)
@deprecated This constant is no longer used since Lucene 4.5.
*/
@Deprecated
public static final int DEFAULT_READ_CHUNK_SIZE = 8192;
protected final File directory; // The underlying filesystem directory
protected final Set<String> staleFiles = synchronizedSet(new HashSet<String>()); // Files written, but not yet sync'ed
private int chunkSize = DEFAULT_READ_CHUNK_SIZE;
// 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());
}
/** 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 if there is a low-level I/O error
*/
protected FSDirectory(File path, LockFactory lockFactory) throws IOException {
// new ctors use always NativeFSLockFactory as default:
if (lockFactory == null) {
lockFactory = new NativeFSLockFactory();
}
directory = getCanonicalPath(path);
if (directory.exists() && !directory.isDirectory())
throw new NoSuchDirectoryException("file '" + directory + "' exists but is not a directory");
setLockFactory(lockFactory);
}
/** 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 MMapDirectory} for most Solaris
* and Windows 64-bit JREs, {@link NIOFSDirectory} for other
* non-Windows JREs, and {@link SimpleFSDirectory} for other
* JREs 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. For optimal performance you should consider using
* {@link MMapDirectory} 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 {
if (Constants.JRE_IS_64BIT && MMapDirectory.UNMAP_SUPPORTED) {
return new MMapDirectory(path, lockFactory);
} else if (Constants.WINDOWS) {
return new SimpleFSDirectory(path, lockFactory);
} else {
return new NIOFSDirectory(path, lockFactory);
}
}
@Override
public void setLockFactory(LockFactory lockFactory) throws IOException {
super.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(directory);
lf.setLockPrefix(null);
} else if (dir.getCanonicalPath().equals(directory.getCanonicalPath())) {
lf.setLockPrefix(null);
}
}
}
/** 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() {
@Override
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 length in bytes of a file in the directory. */
@Override
public long fileLength(String name) throws IOException {
ensureOpen();
File file = new File(directory, name);
final long len = file.length();
if (len == 0 && !file.exists()) {
throw new FileNotFoundException(name);
} else {
return len;
}
}
/** 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);
staleFiles.remove(name);
}
/** Creates an IndexOutput for the file with the given name. */
@Override
public IndexOutput createOutput(String name, IOContext context) throws IOException {
ensureOpen();
ensureCanWrite(name);
return new FSIndexOutput(name);
}
protected void ensureCanWrite(String name) throws IOException {
if (!directory.exists())
if (!directory.mkdirs())
throw new IOException("Cannot create directory: " + directory);
File file = new File(directory, name);
if (file.exists() && !file.delete()) // delete existing, if any
throw new IOException("Cannot overwrite: " + file);
}
/**
* Sub classes should call this method on closing an open {@link IndexOutput}, reporting the name of the file
* that was closed. {@code FSDirectory} needs this information to take care of syncing stale files.
*/
protected void onIndexOutputClosed(String name) {
staleFiles.add(name);
}
@Override
public void sync(Collection<String> names) throws IOException {
ensureOpen();
Set<String> toSync = new HashSet<>(names);
toSync.retainAll(staleFiles);
for (String name : toSync) {
fsync(name);
}
// fsync the directory itsself, but only if there was any file fsynced before
// (otherwise it can happen that the directory does not yet exist)!
if (!toSync.isEmpty()) {
IOUtils.fsync(directory, true);
}
staleFiles.removeAll(toSync);
}
@Override
public String getLockID() {
ensureOpen();
String dirName; // name to be hashed
try {
dirName = directory.getCanonicalPath();
} catch (IOException e) {
throw new RuntimeException(e.toString(), e);
}
int digest = 0;
for(int charIDX=0;charIDX<dirName.length();charIDX++) {
final char ch = dirName.charAt(charIDX);
digest = 31 * digest + ch;
}
return "lucene-" + Integer.toHexString(digest);
}
/** Closes the store to future operations. */
@Override
public synchronized void close() {
isOpen = false;
}
/** @return the underlying filesystem directory */
public File getDirectory() {
ensureOpen();
return directory;
}
/** For debug output. */
@Override
public String toString() {
return this.getClass().getSimpleName() + "@" + directory + " lockFactory=" + getLockFactory();
}
/**
* This setting has no effect anymore.
* @deprecated This is no longer used since Lucene 4.5.
*/
@Deprecated
public final void setReadChunkSize(int chunkSize) {
if (chunkSize <= 0) {
throw new IllegalArgumentException("chunkSize must be positive");
}
this.chunkSize = chunkSize;
}
/**
* This setting has no effect anymore.
* @deprecated This is no longer used since Lucene 4.5.
*/
@Deprecated
public final int getReadChunkSize() {
return chunkSize;
}
final class FSIndexOutput extends OutputStreamIndexOutput {
/**
* The maximum chunk size is 8192 bytes, because {@link FileOutputStream} mallocs
* a native buffer outside of stack if the write buffer size is larger.
*/
static final int CHUNK_SIZE = 8192;
private final String name;
public FSIndexOutput(String name) throws IOException {
super(new FilterOutputStream(new FileOutputStream(new File(directory, name))) {
// This implementation ensures, that we never write more than CHUNK_SIZE bytes:
@Override
public void write(byte[] b, int offset, int length) throws IOException {
while (length > 0) {
final int chunk = Math.min(length, CHUNK_SIZE);
out.write(b, offset, chunk);
length -= chunk;
offset += chunk;
}
}
}, CHUNK_SIZE);
this.name = name;
}
@Override
public void close() throws IOException {
try {
onIndexOutputClosed(name);
} finally {
super.close();
}
}
}
protected void fsync(String name) throws IOException {
IOUtils.fsync(new File(directory, name), false);
}
}