001 /* ============================================================
002 * JRobin : Pure java implementation of RRDTool's functionality
003 * ============================================================
004 *
005 * Project Info: http://www.jrobin.org
006 * Project Lead: Sasa Markovic (saxon@jrobin.org);
007 *
008 * (C) Copyright 2003-2005, by Sasa Markovic.
009 *
010 * Developers: Sasa Markovic (saxon@jrobin.org)
011 *
012 *
013 * This library is free software; you can redistribute it and/or modify it under the terms
014 * of the GNU Lesser General Public License as published by the Free Software Foundation;
015 * either version 2.1 of the License, or (at your option) any later version.
016 *
017 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
018 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
019 * See the GNU Lesser General Public License for more details.
020 *
021 * You should have received a copy of the GNU Lesser General Public License along with this
022 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
023 * Boston, MA 02111-1307, USA.
024 */
025
026 package org.jrobin.core;
027
028 import sun.nio.ch.DirectBuffer;
029
030 import java.io.IOException;
031 import java.nio.MappedByteBuffer;
032 import java.nio.channels.FileChannel;
033 import java.util.Timer;
034 import java.util.TimerTask;
035
036 /**
037 * JRobin backend which is used to store RRD data to ordinary disk files
038 * by using fast java.nio.* package. This is the default backend engine since JRobin 1.4.0.
039 */
040 public class RrdNioBackend extends RrdFileBackend {
041 private static final Timer fileSyncTimer = new Timer(true);
042
043 private MappedByteBuffer byteBuffer;
044 private TimerTask syncTask = new TimerTask() {
045 public void run() {
046 sync();
047 }
048 };
049
050 /**
051 * Creates RrdFileBackend object for the given file path, backed by java.nio.* classes.
052 *
053 * @param path Path to a file
054 * @param readOnly True, if file should be open in a read-only mode. False otherwise
055 * @param syncPeriod See {@link RrdNioBackendFactory#setSyncPeriod(int)} for explanation
056 * @throws IOException Thrown in case of I/O error
057 */
058 protected RrdNioBackend(String path, boolean readOnly, int syncPeriod)
059 throws IOException {
060 super(path, readOnly);
061 try {
062 mapFile();
063 if (!readOnly) {
064 fileSyncTimer.schedule(syncTask, syncPeriod * 1000L, syncPeriod * 1000L);
065 }
066 }
067 catch (IOException ioe) {
068 super.close();
069 throw ioe;
070 }
071 }
072
073 private void mapFile() throws IOException {
074 long length = getLength();
075 if (length > 0) {
076 FileChannel.MapMode mapMode =
077 readOnly ? FileChannel.MapMode.READ_ONLY : FileChannel.MapMode.READ_WRITE;
078 byteBuffer = file.getChannel().map(mapMode, 0, length);
079 }
080 }
081
082 private void unmapFile() {
083 if (byteBuffer != null) {
084 if (byteBuffer instanceof DirectBuffer) {
085 ((DirectBuffer) byteBuffer).cleaner().clean();
086 }
087 byteBuffer = null;
088 }
089 }
090
091 /**
092 * Sets length of the underlying RRD file. This method is called only once, immediately
093 * after a new RRD file gets created.
094 *
095 * @param newLength Length of the RRD file
096 * @throws IOException Thrown in case of I/O error.
097 */
098 protected synchronized void setLength(long newLength) throws IOException {
099 unmapFile();
100 super.setLength(newLength);
101 mapFile();
102 }
103
104 /**
105 * Writes bytes to the underlying RRD file on the disk
106 *
107 * @param offset Starting file offset
108 * @param b Bytes to be written.
109 */
110 protected synchronized void write(long offset, byte[] b) throws IOException {
111 if (byteBuffer != null) {
112 byteBuffer.position((int) offset);
113 byteBuffer.put(b);
114 }
115 else {
116 throw new IOException("Write failed, file " + getPath() + " not mapped for I/O");
117 }
118 }
119
120 /**
121 * Reads a number of bytes from the RRD file on the disk
122 *
123 * @param offset Starting file offset
124 * @param b Buffer which receives bytes read from the file.
125 */
126 protected synchronized void read(long offset, byte[] b) throws IOException {
127 if (byteBuffer != null) {
128 byteBuffer.position((int) offset);
129 byteBuffer.get(b);
130 }
131 else {
132 throw new IOException("Read failed, file " + getPath() + " not mapped for I/O");
133 }
134 }
135
136 /**
137 * Closes the underlying RRD file.
138 *
139 * @throws IOException Thrown in case of I/O error
140 */
141 public synchronized void close() throws IOException {
142 // cancel synchronization
143 try {
144 if (syncTask != null) {
145 syncTask.cancel();
146 }
147 sync();
148 unmapFile();
149 }
150 finally {
151 super.close();
152 }
153 }
154
155 /**
156 * This method forces all data cached in memory but not yet stored in the file,
157 * to be stored in it.
158 */
159 protected synchronized void sync() {
160 if (byteBuffer != null) {
161 byteBuffer.force();
162 }
163 }
164 }