Changeset 17630 for gli/trunk/src/org/greenstone/gatherer/remote/RemoteGreenstoneServer.java

Timestamp:

2008-10-29T20:04:25+13:00 (15 years ago)

Author:

ak19

Message:

1. Previously the GLI client and GLI applet used to have a problem that manifested very rarely and randomly: every so often, one of the gliserver Action commands would get stuck in an infinite wait loop. The current code, after running it about 50 times and not showing this problem anymore, seems to have fixed this. The changes made were to RemoteGreenstoneServer.performAction() where a wait() is now used instead of a timed wait() and the ActionQueue.java class where more methods are now synchronised and the infinite while loop in the Thread's run() method has been reorganised to check for any increase in the size of the action queue at the start. 2. An exit condition is now used instead of an infinite while loop in ActionQueue's run(), so that the loop is terminated when the user cancels or a connect exception occurs. This ends the thread (which is particularly necessary in Applets, else they keep consuming processor time). RemoteGreenstoneServer.performAction() checks for whether the ActionQueue thread has exited and if so GLI's Gatherer exits, otherwise performAction proceeds to add the next action to the queue as before.

File:

• gli/trunk/src/org/greenstone/gatherer/remote/RemoteGreenstoneServer.java (modified) (7 diffs)

gli/trunk/src/org/greenstone/gatherer/remote/RemoteGreenstoneServer.java

@@ -66 +66 @@
 
     public RemoteGreenstoneServer() {
+    // Create the progress_bar first since ActionQueue uses it in its thread 
+    // (the thread will start immediately).
+    progress_bar = new RemoteGreenstoneServer.ProgressBar();
     remote_greenstone_server_action_queue = new ActionQueue();
-    progress_bar = new RemoteGreenstoneServer.ProgressBar();
     }
 
@@ -230 +232 @@
     }
     }
-
+    
 
     // ----------------------------------------------------------------------------------------------------
@@ -240 +242 @@
     private String performAction(RemoteGreenstoneServerAction remote_greenstone_server_action)
     {
+    // Check for whether the queue thread stopped running because 
+    // the user cancelled out. If so, exit GLI.
+    if(remote_greenstone_server_action_queue.hasExited()) {
+        remote_greenstone_server_action_queue.clear();
+        //remote_greenstone_server_action_queue = null;
+        Gatherer.exit();
+        return "";
+    }
+
     // Add the action to the queue
     remote_greenstone_server_action_queue.addAction(remote_greenstone_server_action);
+    String threadName = Thread.currentThread().getName();
 
     // If we're running in the GUI thread we must return immediately
     // We cannot wait for the action to complete because this will block any GUI updates
     if (SwingUtilities.isEventDispatchThread()) {
-        System.err.println("WARNING: In event dispatch thread, returning immediately...");
+        System.err.println(threadName 
+                   + "\tACTION QUEUED: In event dispatch thread, returning immediately...\n\t" 
+                   + remote_greenstone_server_action);
         return null;
     }
 
     // Otherwise wait until the action is processed
-    while (!remote_greenstone_server_action.processed) {
+    try {
         synchronized (remote_greenstone_server_action) {
-        try {
+        while(!remote_greenstone_server_action.processed) {
+            //System.err.println("Waiting for action to complete...: " + remote_greenstone_server_action);
             DebugStream.println("Waiting for action to complete...");
-            remote_greenstone_server_action.wait(500);
+            remote_greenstone_server_action.wait(); // wait to be notified when the action has been processed 
         }
-        catch (InterruptedException exception) {}
-        }
+        }
+    } catch (Exception e) {
+        System.err.println("RemoteGreenstoneServer.performAction() - exception: " + e);
+        e.printStackTrace();
     }
 
@@ -285 +302 @@
     }
 
-
-    public void setAction(String action)
+    /** synchronized to avoid conflicts since several threads access this */
+    synchronized public void setAction(String action)
     {
         if (action != null) {
@@ -310 +327 @@
     }
     
-    public RemoteGreenstoneServer.ProgressBar getProgressBar()
+    /** synchronized to avoid conflicts since several threads access this */
+    synchronized public RemoteGreenstoneServer.ProgressBar getProgressBar()
     {
     return progress_bar;
@@ -327 +345 @@
         remote_greenstone_server_authentication = new RemoteGreenstoneServerAuthenticator().getAuthentication();
     }
-
+    
 
     static private class RemoteGreenstoneServerAuthenticator
@@ -366 +384 @@
         }
         catch (Exception exception) {
+        System.err.println("Exception occurred when authenticating the user: " + exception);
         DebugStream.printStackTrace(exception);
         }