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Monitoring of JavaEE applications
/* ============================================================
* JRobin : Pure java implementation of RRDTool's functionality
* ============================================================
*
* Project Info: http://www.jrobin.org
* Project Lead: Sasa Markovic ([email protected]);
*
* (C) Copyright 2003-2005, by Sasa Markovic.
*
* Developers: Sasa Markovic ([email protected])
*
*
* This library is free software; you can redistribute it and/or modify it under the terms
* of the GNU Lesser General Public License as published by the Free Software Foundation;
* either version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*/
package net.bull.javamelody.internal.model;
import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Timer;
import java.util.TimerTask;
import org.jrobin.core.RrdFileBackend;
import sun.nio.ch.DirectBuffer; // NOPMD
/**
* JRobin backend which is used to store RRD data to ordinary disk files
* by using fast java.nio.* package. This is the default backend engine since JRobin 1.4.0.
*/
public class RrdNioBackend extends RrdFileBackend {
private static final Object THE_UNSAFE = getTheUnsafe();
private static final Method JAVA9_INVOKE_CLEANER = getJava9InvokeCleaner();
private static Timer fileSyncTimer;
private MappedByteBuffer byteBuffer;
private final TimerTask syncTask = new TimerTask() {
@Override
public void run() {
sync();
}
};
/**
* Creates RrdFileBackend object for the given file path, backed by java.nio.* classes.
*
* @param path Path to a file
* @param readOnly True, if file should be open in a read-only mode. False otherwise
* @param syncPeriod See {@link RrdNioBackendFactory#setSyncPeriod(int)} for explanation
* @throws IOException Thrown in case of I/O error
*/
protected RrdNioBackend(String path, boolean readOnly, int syncPeriod) throws IOException {
super(path, readOnly);
try {
mapFile();
if (!readOnly) {
fileSyncTimer.schedule(syncTask, syncPeriod * 1000L, syncPeriod * 1000L);
}
} catch (final IOException ioe) {
super.close(); // NOPMD
throw ioe;
} catch (final IllegalStateException e) {
// issue #592 (IllegalStateException: Timer already cancelled)
unmapFile();
super.close(); // NOPMD
throw e;
}
}
/**
* @return The timer to synchronize files.
*/
public static Timer getFileSyncTimer() {
return fileSyncTimer;
}
/**
* Sets the timer.
* @param timer timer to synchronize files.
*/
public static void setFileSyncTimer(Timer timer) {
fileSyncTimer = timer;
}
private void mapFile() throws IOException {
final long length = getLength();
if (length > 0) {
final FileChannel.MapMode mapMode =
// (issue 328) readOnly ? FileChannel.MapMode.READ_ONLY :
FileChannel.MapMode.READ_WRITE;
byteBuffer = file.getChannel().map(mapMode, 0, length);
}
}
private void unmapFile() {
if (byteBuffer != null) {
if (JAVA9_INVOKE_CLEANER == null || THE_UNSAFE == null) {
if (byteBuffer instanceof DirectBuffer) {
// for Java 8 and before
((DirectBuffer) byteBuffer).cleaner().clean();
}
} else {
// for Java 9 and later:
// sun.nio.ch.DirectBuffer methods are not accessible,
// so the new sun.misc.Unsafe.theUnsafe.invokeCleaner(ByteBuffer) is used.
// See https://bugs.openjdk.java.net/browse/JDK-8171377
try {
JAVA9_INVOKE_CLEANER.invoke(THE_UNSAFE, byteBuffer);
} catch (final Exception e) {
throw new IllegalStateException(e);
}
}
byteBuffer = null;
}
}
private static Object getTheUnsafe() {
try {
final Class unsafeClass = Class.forName("sun.misc.Unsafe");
final Field theUnsafeField = unsafeClass.getDeclaredField("theUnsafe");
theUnsafeField.setAccessible(true);
return theUnsafeField.get(null);
} catch (final Exception e) {
return null;
}
}
private static Method getJava9InvokeCleaner() {
try {
final Class unsafeClass = Class.forName("sun.misc.Unsafe");
return unsafeClass.getMethod("invokeCleaner", ByteBuffer.class);
} catch (final Exception e) {
return null;
}
}
/**
* Sets length of the underlying RRD file. This method is called only once, immediately
* after a new RRD file gets created.
*
* @param newLength Length of the RRD file
* @throws IOException Thrown in case of I/O error.
*/
@Override
protected synchronized void setLength(long newLength) throws IOException {
unmapFile();
super.setLength(newLength);
mapFile();
}
/**
* Writes bytes to the underlying RRD file on the disk
*
* @param offset Starting file offset
* @param b Bytes to be written.
*/
@Override
protected synchronized void write(long offset, byte[] b) throws IOException {
if (byteBuffer != null) {
byteBuffer.position((int) offset);
byteBuffer.put(b);
} else {
throw new IOException("Write failed, file " + getPath() + " not mapped for I/O");
}
}
/**
* Reads a number of bytes from the RRD file on the disk
*
* @param offset Starting file offset
* @param b Buffer which receives bytes read from the file.
*/
@Override
protected synchronized void read(long offset, byte[] b) throws IOException {
if (byteBuffer != null) {
byteBuffer.position((int) offset);
byteBuffer.get(b);
} else {
throw new IOException("Read failed, file " + getPath() + " not mapped for I/O");
}
}
/**
* Closes the underlying RRD file.
*
* @throws IOException Thrown in case of I/O error
*/
@Override
public synchronized void close() throws IOException {
// cancel synchronization
try {
if (syncTask != null) {
syncTask.cancel();
}
sync();
unmapFile();
} finally {
super.close();
}
}
/**
* This method forces all data cached in memory but not yet stored in the file,
* to be stored in it.
*/
protected synchronized void sync() {
if (byteBuffer != null) {
byteBuffer.force();
}
}
}