NotificationProcessor


1   /*
2    * Copyright � 2004, Rob Gordon.
3    */
4   package org.oddjob.jmx.client;
5   
6   import java.util.LinkedList  ;
7   
8   import org.apache.log4j.Logger;
9   
10  /**
11   * Process notifications from the server. Additionally this will asynchronously
12   * perform a resync check. This is because it appears possible to 
13   * occasionally miss the first few notifications when creating a new node.
14   * 
15   * @author Rob Gordon.
16   */
17  public class NotificationProcessor extends Thread   {
18      private static final Logger logger = Logger.getLogger(NotificationProcessor.class);
19      
20      private final LinkedList   notifications = new LinkedList  ();
21      private final LinkedList   resyncChecks = new LinkedList  ();
22  
23      synchronized public void enqueue(Runnable   o) {
24          if (isInterrupted()) {
25              // late notifications
26              return;
27          }
28          notifications.add(o);
29          notify();
30      }
31  
32      class Pair {
33          final ClientNode clientNode;
34          final long time;
35          Pair(ClientNode clientNode) {
36              this.clientNode = clientNode;
37              this.time = System.currentTimeMillis();
38          }
39      }
40      
41      synchronized public void check(ClientNode clientNode) {
42          if (isInterrupted()) {
43              // late notifications
44              return;
45          }       
46          logger.debug("Resync check added for [" + clientNode.toString() + "]");
47          resyncChecks.add(new Pair(clientNode));
48          notifyAll();
49      }
50      
51      public void run() {
52          while (!isInterrupted()) {
53              Runnable   notification = null;
54              ClientNode resyncCheck = null;
55              int backlog = 0;
56              int checks = 0;
57              synchronized (this) {
58                  backlog = notifications.size();
59                  if (backlog > 0) {
60                      notification = (Runnable  ) notifications.removeFirst();
61                      --backlog;
62                  } else {
63                      long sleep = 0;
64                      checks = resyncChecks.size();
65                      if (checks > 0) {
66                          Pair pair = (Pair) resyncChecks.getFirst();
67                          sleep = pair.time - System.currentTimeMillis() + 5000;
68                          if (sleep < 1) {
69                              pair = (Pair) resyncChecks.removeFirst();
70                              resyncCheck = pair.clientNode;
71                              --checks;
72                          }
73                      }
74                      if (resyncCheck == null) {
75                          try {
76                              wait(sleep);
77                          }
78                          catch (InterruptedException   e) {
79                              notifications.clear();
80                              resyncChecks.clear();
81                              return;
82                          }
83                      }
84                  }
85              }
86              logger.debug("Processing, backlog is [" + backlog 
87                      + "], outstanding checks are [" + checks + "]");
88              if (notification != null) {
89                  try {
90                      notification.run();
91                  } catch (Throwable   t) {
92                      logger.error("Failed processing:", t);
93                  }
94              }
95              else if (resyncCheck != null) {
96                  try {
97                      resyncCheck.resync();
98                  } catch (Throwable   t) {
99                      logger.error("Failed check:", t);
100                 }
101             }
102         }
103         logger.debug("Stopping.");
104     }
105     
106     synchronized public int size() {
107         return notifications.size();
108     }
109     
110 }
111
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