1 /*
2 * $Id: VMStatSwappingDetectionThread.java 178 2010-10-31 18:01:20Z roland $
3 * Copyright (C) 2007 Roland Krueger
4 *
5 * Author: Roland Krueger (www.rolandkrueger.info)
6 *
7 * This file is part of RoKlib.
8 *
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public License
11 * as published by the Free Software Foundation; either version 2.1 of
12 * the License, or (at your option) any later version.
13 *
14 * This library is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
22 * USA
23 */
24 package info.rolandkrueger.roklib.system;
25
26 import java.io.BufferedReader;
27 import java.io.File;
28 import java.io.IOException;
29 import java.io.InputStreamReader;
30 import java.util.logging.Logger;
31 import java.util.regex.Matcher;
32 import java.util.regex.Pattern;
33
34 /**
35 * This class is a concrete implementation of the abstract class
36 * {@link MemorySwappingDetectionThread} where the program <code>vmstat</code>
37 * is used for detecting memory swapping. When the thread is started,
38 * <code>vmstat</code> is invoked with an update delay of a configurable number
39 * of seconds. The thread will then evaluate the output of <code>vmstat</code>
40 * upon each update. If the swap in/out column of <code>vmstat</code>'s output
41 * differs from 0 the object registered as {@link MemorySwappingEventListener}
42 * will be notified of that event. <br>
43 * <br>
44 * Note: Detecting memory paging with an external, platform-dependent tool such
45 * as <code>vmstat</code> is of course detrimental to the application's
46 * portability. This strategy was chosen, though, since it offered an easy to
47 * implement method for swapping detection. Unfortunately, the Java language as
48 * yet doesn't offer any general machanisms to detect these memory paging
49 * situations in a portable way. If there are any better ways to cope with that
50 * in the future, an appropriate method can be implemented as a subclass of
51 * {@link MemorySwappingDetectionThread}.
52 *
53 * @author Roland Krueger
54 */
55 public class VMStatSwappingDetectionThread extends MemorySwappingDetectionThread
56 {
57 protected static Logger sLogger = Logger.getLogger (VMStatSwappingDetectionThread.class
58 .getPackage ().getName ());
59 private final static String CMD_STRING = "%s %d";
60
61 /**
62 * Regular expression that extracts the swap in and swap out columns of the
63 * <code>vmstat</code> output.
64 */
65 private final static Pattern SWAP_PATTERN = Pattern
66 .compile ("^(?:\\s*\\d+){6}\\s*(\\d+)\\s*(\\d+).*$");
67
68 private String mVMStatBinaryLocation;
69 private int mSamplingRate;
70 private Process mVMStatProcess;
71 private BufferedReader mProcessReader;
72 private String mLine;
73 private Matcher mMatcher;
74
75 /**
76 * Constructor.
77 *
78 * @param listener
79 * object that implements the {@link MemorySwappingEventListener}
80 * interface
81 * @param vmstatBinaryLocation
82 * the location of the <code>vmstat</code> command. This is usually
83 * <code>/usr/bin/vmstat</code>.
84 * @param samplingRate
85 * the update delay for <code>vmstat</code>
86 */
87 public VMStatSwappingDetectionThread (MemorySwappingEventListener listener,
88 String vmstatBinaryLocation, int samplingRate)
89 {
90 super (listener);
91 mVMStatBinaryLocation = vmstatBinaryLocation;
92 if (mVMStatBinaryLocation.matches ("\\s"))
93 throw new IllegalArgumentException (
94 "Using a whitespace character in the vmstat binary location string is not allowed.");
95
96 File vmstatBinary = new File (mVMStatBinaryLocation);
97 if (! vmstatBinary.canRead ())
98 throw new IllegalArgumentException ("Unable to read the given file for the vmstat binary.");
99
100 mSamplingRate = samplingRate;
101 if (samplingRate <= 0)
102 throw new IllegalArgumentException ("Sampling rate must be at least 1.");
103 }
104
105 /**
106 * Starts the <code>vmstat</code> command in an own process.
107 *
108 * @return <code>true</code> if the process was successfully started
109 */
110 public synchronized boolean startProcess ()
111 {
112 // start vmstat and parse its output
113 ProcessBuilder procBuilder = new ProcessBuilder (String.format (CMD_STRING,
114 mVMStatBinaryLocation, mSamplingRate).split (" "));
115 procBuilder.redirectErrorStream (true);
116
117 try
118 {
119 mVMStatProcess = procBuilder.start ();
120 mProcessReader = new BufferedReader (new InputStreamReader (mVMStatProcess.getInputStream ()));
121 } catch (IOException ioExc)
122 {
123 sLogger.warning ("Unable to start vmstat process with binary :" + mVMStatBinaryLocation);
124 return false;
125 }
126 super.start ();
127 return true;
128 }
129
130 @Override
131 protected boolean isSwapEventDetected ()
132 {
133 if (mProcessReader == null)
134 throw new IllegalStateException ("Thread must be started with startProcess().");
135 try
136 {
137 mLine = mProcessReader.readLine ();
138 if (mLine == null)
139 {
140 sLogger.info ("vmstat process has finished.");
141 stopThread ();
142 return false;
143 }
144 } catch (IOException e)
145 {
146 stopThread ();
147 return false;
148 }
149
150 mMatcher = SWAP_PATTERN.matcher (mLine);
151 if (mMatcher.matches ())
152 {
153 if (! mMatcher.group (1).equals ("0") || ! mMatcher.group (2).equals ("0")) return true;
154 }
155
156 return false;
157 }
158
159 @Override
160 protected void stopThreadImpl ()
161 {
162 if (mVMStatProcess != null)
163 {
164 sLogger.info ("Stopping vmstat process.");
165 mVMStatProcess.destroy ();
166 }
167 }
168
169 }