Source Code Cross Referenced for Scheduler.java in  » Net » JGroups-2.4.1-sp3 » org » jgroups » util » Java Source Code / Java DocumentationJava Source Code and Java Documentation

Java Source Code / Java Documentation
1. 6.0 JDK Core
2. 6.0 JDK Modules
3. 6.0 JDK Modules com.sun
4. 6.0 JDK Modules com.sun.java
5. 6.0 JDK Modules sun
6. 6.0 JDK Platform
7. Ajax
8. Apache Harmony Java SE
9. Aspect oriented
10. Authentication Authorization
11. Blogger System
12. Build
13. Byte Code
14. Cache
15. Chart
16. Chat
17. Code Analyzer
18. Collaboration
19. Content Management System
20. Database Client
21. Database DBMS
22. Database JDBC Connection Pool
23. Database ORM
24. Development
25. EJB Server geronimo
26. EJB Server GlassFish
27. EJB Server JBoss 4.2.1
28. EJB Server resin 3.1.5
29. ERP CRM Financial
30. ESB
31. Forum
32. GIS
33. Graphic Library
34. Groupware
35. HTML Parser
36. IDE
37. IDE Eclipse
38. IDE Netbeans
39. Installer
40. Internationalization Localization
41. Inversion of Control
42. Issue Tracking
43. J2EE
44. JBoss
45. JMS
46. JMX
47. Library
48. Mail Clients
49. Net
50. Parser
51. PDF
52. Portal
53. Profiler
54. Project Management
55. Report
56. RSS RDF
57. Rule Engine
58. Science
59. Scripting
60. Search Engine
61. Security
62. Sevlet Container
63. Source Control
64. Swing Library
65. Template Engine
66. Test Coverage
67. Testing
68. UML
69. Web Crawler
70. Web Framework
71. Web Mail
72. Web Server
73. Web Services
74. Web Services apache cxf 2.0.1
75. Web Services AXIS2
76. Wiki Engine
77. Workflow Engines
78. XML
79. XML UI
Java
Java Tutorial
Java Open Source
Jar File Download
Java Articles
Java Products
Java by API
Photoshop Tutorials
Maya Tutorials
Flash Tutorials
3ds-Max Tutorials
Illustrator Tutorials
GIMP Tutorials
C# / C Sharp
C# / CSharp Tutorial
C# / CSharp Open Source
ASP.Net
ASP.NET Tutorial
JavaScript DHTML
JavaScript Tutorial
JavaScript Reference
HTML / CSS
HTML CSS Reference
C / ANSI-C
C Tutorial
C++
C++ Tutorial
Ruby
PHP
Python
Python Tutorial
Python Open Source
SQL Server / T-SQL
SQL Server / T-SQL Tutorial
Oracle PL / SQL
Oracle PL/SQL Tutorial
PostgreSQL
SQL / MySQL
MySQL Tutorial
VB.Net
VB.Net Tutorial
Flash / Flex / ActionScript
VBA / Excel / Access / Word
XML
XML Tutorial
Microsoft Office PowerPoint 2007 Tutorial
Microsoft Office Excel 2007 Tutorial
Microsoft Office Word 2007 Tutorial
Java Source Code / Java Documentation » Net » JGroups 2.4.1 sp3 » org.jgroups.util 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // $Id: Scheduler.java,v 1.13.2.1 2007/03/08 10:23:05 belaban Exp $
002:
003:        package org.jgroups.util;
004:
005:        import org.apache.commons.logging.Log;
006:        import org.apache.commons.logging.LogFactory;
007:        import org.jgroups.Global;
008:
009:        /**
010:         * Implementation of a priority scheduler. The scheduler maintains a queue to the end of which
011:         * all tasks are added. It continually looks at the first queue element, assigns a thread to
012:         * it, runs the thread and waits for completion. When a new <em>priority task</em> is added,
013:         * it will be added to the head of the queue and the scheduler will be interrupted. In this
014:         * case, the currently handled task is suspended, and the one at the head of the queue
015:         * handled. This is recursive: a priority task can always be interrupted by another priority
016:         * task.  Resursion ends when no more priority tasks are added, or when the thread pool is
017:         * exhausted.
018:         * 
019:         * @author Bela Ban
020:         */
021:        public class Scheduler implements  Runnable {
022:            final Queue queue = new Queue();
023:            Thread sched_thread = null;
024:            Task current_task = null;
025:            ThreadPool pool = null;
026:            SchedulerListener listener = null;
027:
028:            protected static final Log log = LogFactory.getLog(Scheduler.class);
029:
030:            /** Process items on the queue concurrently. The default is to wait until the processing of an item
031:             * has completed before fetching the next item from the queue. Note that setting this to true
032:             * may destroy the properties of a protocol stack, e.g total or causal order may not be
033:             * guaranteed. Set this to true only if you know what you're doing ! */
034:            boolean concurrent_processing = false;
035:
036:            /** max number of threads, will only be allocated when needed */
037:            int NUM_THREADS = 128;
038:
039:            static final int WAIT_FOR_THREAD_AVAILABILITY = 3000;
040:            static final int THREAD_JOIN_TIMEOUT = 1000;
041:
042:            public Scheduler() {
043:                String tmp = Util.getProperty(
044:                        new String[] { Global.SCHEDULER_MAX_THREADS }, null,
045:                        null, false, "128");
046:                this .NUM_THREADS = Integer.parseInt(tmp);
047:            }
048:
049:            public Scheduler(int num_threads) {
050:                this .NUM_THREADS = num_threads;
051:            }
052:
053:            public void setListener(SchedulerListener l) {
054:                listener = l;
055:            }
056:
057:            public boolean getConcurrentProcessing() {
058:                return concurrent_processing;
059:            }
060:
061:            public void setConcurrentProcessing(boolean process_concurrently) {
062:                this .concurrent_processing = process_concurrently;
063:            }
064:
065:            public void run() {
066:                while (sched_thread != null) {
067:                    if (queue.closed())
068:                        break;
069:                    try {
070:                        current_task = (Task) queue.peek(); // get the first task in the queue (blocks until available)
071:                        if (current_task == null) { // @remove
072:                            if (log.isWarnEnabled())
073:                                log.warn("current task is null, queue.size()="
074:                                        + queue.size() + ", queue.closed()="
075:                                        + queue.closed() + ", continuing");
076:                            continue;
077:                        }
078:
079:                        if (current_task.suspended) {
080:                            current_task.suspended = false;
081:                            current_task.thread.resume();
082:                            if (listener != null)
083:                                listener.resumed(current_task.thread,
084:                                        current_task.target);
085:                        } else {
086:                            if (current_task.thread == null) {
087:                                current_task.thread = pool.getThread();
088:                                if (current_task.thread == null) { // thread pool exhausted
089:                                    if (log.isWarnEnabled())
090:                                        log
091:                                                .warn("thread pool exhausted, waiting for "
092:                                                        + WAIT_FOR_THREAD_AVAILABILITY
093:                                                        + "ms before retrying");
094:                                    Util.sleep(WAIT_FOR_THREAD_AVAILABILITY);
095:                                    continue;
096:                                }
097:                            }
098:
099:                            // if we get here, current_task.thread and current_task.target are guaranteed to be non-null
100:                            if (listener != null)
101:                                listener.started(current_task.thread,
102:                                        current_task.target);
103:                            if (current_task.thread
104:                                    .assignTask(current_task.target) == false)
105:                                continue;
106:                        }
107:
108:                        if (sched_thread.isInterrupted()) { // will continue at "catch(InterruptedException)" below
109:                            // sched_thread.interrupt();
110:
111:                            // changed on suggestion from Victor Cardoso: sched_thread.interrupt() does *not* throw an
112:                            // InterruptedException, so we don't land in the catch clause, but rather execute the code below
113:                            // (which we don't want) - bela April 15 2004
114:
115:                            throw new InterruptedException();
116:                        }
117:
118:                        if (concurrent_processing == false) { // this is the default: process serially
119:                            synchronized (current_task.thread) {
120:                                while (!current_task.thread.done()
121:                                        && !current_task.thread.suspended)
122:                                    current_task.thread.wait();
123:                            }
124:                            if (listener != null)
125:                                listener.stopped(current_task.thread,
126:                                        current_task.target);
127:                        }
128:                        queue.removeElement(current_task);
129:                    } catch (InterruptedException interrupted) {
130:                        if (sched_thread == null || queue.closed())
131:                            break;
132:                        if (current_task.thread != null) {
133:                            current_task.thread.suspend();
134:                            if (listener != null)
135:                                listener.suspended(current_task.thread,
136:                                        current_task.target);
137:                            current_task.suspended = true;
138:                        }
139:                        Thread.interrupted(); // clears the interrupt-flag
140:                    } catch (QueueClosedException closed_ex) {
141:                        return;
142:                    } catch (Throwable ex) {
143:                        if (log.isErrorEnabled())
144:                            log.error("exception=" + Util.print(ex));
145:                    }
146:                }
147:                if (log.isTraceEnabled())
148:                    log.trace("scheduler thread terminated");
149:            }
150:
151:            public void addPrio(Runnable task) {
152:                Task new_task = new Task(task);
153:                boolean do_interrupt = false;
154:
155:                try {
156:                    synchronized (queue) { // sync against add()
157:                        if (queue.size() == 0)
158:                            queue.add(new_task);
159:                        else {
160:                            queue.addAtHead(new_task);
161:                            do_interrupt = true;
162:                        }
163:                    }
164:                    if (do_interrupt) // moved out of 'synchronized(queue)' to minimize lock contention
165:                        sched_thread.interrupt();
166:                } catch (Throwable e) {
167:                    if (log.isErrorEnabled())
168:                        log.error("exception=" + e);
169:                }
170:            }
171:
172:            public void add(Runnable task) {
173:                Task new_task = new Task(task);
174:
175:                try {
176:                    synchronized (queue) { // sync against addPrio()
177:                        queue.add(new_task);
178:                    }
179:                } catch (Exception e) {
180:                    if (log.isErrorEnabled())
181:                        log.error("exception=" + e);
182:                }
183:            }
184:
185:            public void start() {
186:                if (queue.closed())
187:                    queue.reset();
188:                if (sched_thread == null) {
189:                    pool = new ThreadPool(NUM_THREADS);
190:                    sched_thread = new Thread(this , "Scheduler main thread");
191:                    sched_thread.setDaemon(true);
192:                    sched_thread.start();
193:                }
194:            }
195:
196:            /**
197:             * Stop the scheduler thread. The thread may be waiting for its next task (queue.peek()) or it may be waiting on
198:             * the currently executing thread. In the first case, closing the queue will throw a QueueClosed exception which
199:             * terminates the scheduler thread. In the second case, after closing the queue, we interrupt the scheduler thread,
200:             * which then checks whether the queue is closed. If this is the case, the scheduler thread terminates.
201:             */
202:            public void stop() {
203:                Thread tmp = null;
204:
205:                // 1. Close the queue
206:                queue.close(false); // will stop thread at next peek();
207:
208:                // 2. Interrupt the scheduler thread
209:                if (sched_thread != null && sched_thread.isAlive()) {
210:                    tmp = sched_thread;
211:                    sched_thread = null;
212:                    tmp.interrupt();
213:                    try {
214:                        tmp.join(THREAD_JOIN_TIMEOUT);
215:                    } catch (Exception ex) {
216:                    }
217:
218:                    if (tmp.isAlive())
219:                        if (log.isErrorEnabled())
220:                            log
221:                                    .error("scheduler thread is still not dead  !!!");
222:                }
223:                sched_thread = null;
224:
225:                // 3. Delete the thread pool
226:                if (pool != null) {
227:                    pool.destroy();
228:                    pool = null;
229:                }
230:            }
231:
232:            public static class Task {
233:                ReusableThread thread = null;
234:                Runnable target = null;
235:                boolean suspended = false;
236:
237:                Task(Runnable target) {
238:                    this .target = target;
239:                }
240:
241:                public String toString() {
242:                    return "[thread=" + thread + ", target=" + target
243:                            + ", suspended=" + suspended + ']';
244:                }
245:            }
246:
247:        }
www.java2java.com | Contact Us
Copyright 2009 - 12 Demo Source and Support. All rights reserved.
All other trademarks are property of their respective owners.