1 /***
2 * Redistribution and use of this software and associated documentation
3 * ("Software"), with or without modification, are permitted provided
4 * that the following conditions are met:
5 *
6 * 1. Redistributions of source code must retain copyright
7 * statements and notices. Redistributions must also contain a
8 * copy of this document.
9 *
10 * 2. Redistributions in binary form must reproduce the
11 * above copyright notice, this list of conditions and the
12 * following disclaimer in the documentation and/or other
13 * materials provided with the distribution.
14 *
15 * 3. The name "Exolab" must not be used to endorse or promote
16 * products derived from this Software without prior written
17 * permission of Exoffice Technologies. For written permission,
18 * please contact info@exolab.org.
19 *
20 * 4. Products derived from this Software may not be called "Exolab"
21 * nor may "Exolab" appear in their names without prior written
22 * permission of Exoffice Technologies. Exolab is a registered
23 * trademark of Exoffice Technologies.
24 *
25 * 5. Due credit should be given to the Exolab Project
26 * (http://www.exolab.org/).
27 *
28 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
29 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
30 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
31 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
32 * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
33 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
34 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
35 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
37 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
39 * OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Copyright 2000-2004 (C) Exoffice Technologies Inc. All Rights Reserved.
42 */
43 package org.exolab.jms.scheduler;
44
45 import EDU.oswego.cs.dl.util.concurrent.LinkedQueue;
46 import EDU.oswego.cs.dl.util.concurrent.PooledExecutor;
47 import org.exolab.jms.common.threads.ThreadPoolFactory;
48 import org.exolab.jms.config.Configuration;
49 import org.exolab.jms.config.SchedulerConfiguration;
50 import org.exolab.jms.service.Service;
51
52
53 /***
54 * The scheduler is responsible for executing {@link Runnable} objects using a
55 * thread pool. Clients can add these objects to the scheduler and the scheduler
56 * will, in fifo order, execute them. If there are no threads currently
57 * available, the runnable will wait for one to become available.
58 * <p/>
59 * A client can add or remove {@link Runnable} objects.
60 *
61 * @author <a href="mailto:mourikis@intalio.com">Jim Mourikis</a>
62 * @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
63 * @author <a href="mailto:jima@comware.com.au">Jim Alateras</a>
64 * @version $Revision: 1.3 $ $Date: 2006/02/23 11:17:39 $
65 */
66 public class Scheduler extends Service {
67
68 /***
69 * The thread pool used by the scheduler.
70 */
71 private final PooledExecutor _threads;
72
73 /***
74 * This is the minimum number of threads that can be used to configure the
75 * scheduler. If a lower nmber is specified then it defaults to this value
76 */
77 private final static int MIN_THREAD_COUNT = 2;
78
79 /***
80 * Unique name identifyting this sevice
81 */
82 private static final String SCHEDULER_NAME = "Scheduler";
83
84 /***
85 * Construct a new <code>Scheduler</code>.
86 *
87 * @param config the configuration
88 * @param factory the thread pool factory
89 */
90 public Scheduler(Configuration config, ThreadPoolFactory factory) {
91 super(SCHEDULER_NAME);
92
93 SchedulerConfiguration schedConfig =
94 config.getSchedulerConfiguration();
95
96 int count = schedConfig.getMaxThreads();
97 if (count < MIN_THREAD_COUNT) {
98 count = MIN_THREAD_COUNT;
99 }
100
101
102 _threads = factory.create(SCHEDULER_NAME, new LinkedQueue(), count);
103 _threads.setMinimumPoolSize(count);
104 _threads.setKeepAliveTime(-1);
105 }
106
107 /***
108 * Add a Runnable object to the scheduler queue. When a thread becomes
109 * available, it will be executed.
110 *
111 * @param task the task to execute
112 */
113 public void execute(Runnable task) throws InterruptedException {
114 _threads.execute(task);
115 }
116
117 /***
118 * Stop the service.
119 */
120 protected void doStop() {
121 _threads.shutdownAfterProcessingCurrentlyQueuedTasks();
122 }
123
124 }