New very safe shutdown scheme. An Invoker.Unit runs on both the Invoker

and dobj thread until they're both empty (or it has been passed 50 times)
and then shuts the threads down.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@2744 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/util/Invoker.java

@@ -1,5 +1,5 @@
 //
-// $Id: Invoker.java,v 1.7 2003/04/10 21:04:55 mdb Exp $
+// $Id: Invoker.java,v 1.8 2003/08/08 03:11:55 ray Exp $
 
 package com.threerings.presents.util;
 
@@ -115,55 +115,47 @@ public class Invoker extends LoopingThread
     public void iterate ()
     {
         // pop the next item off of the queue
-        Object unit = _queue.get();
+        Unit unit = (Unit) _queue.get();
 
-        // if it's a unit, we invoke it
-        if (unit instanceof Runnable) {
-            long start;
+        long start;
+        if (PERF_TRACK) {
+            start = System.currentTimeMillis();
+            _unitsRun++;
+        }
+
+        try {
+            if (unit.invoke()) {
+                // if it returned true, we post it to the dobjmgr
+                // thread to invoke the result processing
+                _omgr.postUnit(unit);
+            }
+
+            // track some performance metrics
             if (PERF_TRACK) {
-                start = System.currentTimeMillis();
-                _unitsRun++;
+                long duration = System.currentTimeMillis() - start;
+                Object key = unit.getClass();
+
+                Histogram histo = (Histogram)_tracker.get(key);
+                if (histo == null) {
+                    // track in buckets of 50ms up to 500ms
+                    _tracker.put(key, histo = new Histogram(0, 50, 10));
+                }
+                histo.addValue((int)duration);
             }
 
-            try {
-                if (((Unit)unit).invoke()) {
-                    // if it returned true, we post it to the dobjmgr
-                    // thread to invoke the result processing
-                    _omgr.postUnit((Runnable)unit);
-                }
-
-                // track some performance metrics
-                if (PERF_TRACK) {
-                    long duration = System.currentTimeMillis() - start;
-                    Object key = unit.getClass();
-
-                    Histogram histo = (Histogram)_tracker.get(key);
-                    if (histo == null) {
-                        // track in buckets of 50ms up to 500ms
-                        _tracker.put(key, histo = new Histogram(0, 50, 10));
-                    }
-                    histo.addValue((int)duration);
-                }
-
-            } catch (Exception e) {
-                Log.warning("Invocation unit failed [unit=" + unit + "].");
-                Log.logStackTrace(e);
-            }
-
-        } else {
-            // if it's not a runnable, it was just an object posted to our
-            // queue to wake us up and tell us to go away
-            _running = false;
+        } catch (Exception e) {
+            Log.warning("Invocation unit failed [unit=" + unit + "].");
+            Log.logStackTrace(e);
         }
     }
 
-    // documentation inherited
+    /**
+     * Will do a sophisticated shutdown of both itself and the DObjectManager
+     * thread.
+     */
     public void shutdown ()
     {
-        // we do some custom shutdown business: add a non-runnable to the
-        // queue which, when the invoker gets to it, will cause it to shut
-        // itself down
-        _queue.append(new Integer(0));
+        _queue.append(new ShutdownUnit());
     }
 
     // documentation inherited from interface
@@ -182,6 +174,60 @@ public class Invoker extends LoopingThread
         }
     }
 
+    /**
+     * This unit gets posted back and forth between the invoker and DObjectMgr
+     * until both of their queues are empty and they can both be safely
+     * shutdown.
+     */
+    protected class ShutdownUnit extends Unit
+    {
+        // run on the invoker thread
+        public boolean invoke ()
+        {
+            // if the invoker queue is not empty, we put ourselves back on it
+            if (_queue.hasElements()) {
+                System.err.println("invoker not empty");
+                postUnit(this);
+                return false;
+
+            } else {
+                // the invoker is empty, let's go over to the omgr
+                System.err.println("invoker empty, passing");
+                _passCount++;
+                return true;
+            }
+        }
+
+        // run on the dobj thread
+        public void handleResult ()
+        {
+            // if the queue isn't empty, re-post
+            if (!_omgr.queueIsEmpty()) {
+                _omgr.postUnit(this);
+
+            // if both queues are empty, or we've passed 50 times, end it all
+            } else if (!_queue.hasElements() || (_passCount >= 50)) {
+                // shut it down!
+                _omgr.harshShutdown(); // end the dobj thread
+                // and since we're ending the invoker from the dobjmgr
+                // we need to post one last event to the invoker
+                postUnit(new Unit() {
+                    public boolean invoke () {
+                        _running = false; // end this thread
+                        return false;
+                    }
+                });
+
+            // otherwise, we need to pass back to the invoker
+            } else {
+                postUnit(this);
+            }
+        }
+
+        /** The number of times we've been passed to the object manager. */
+        protected int _passCount = 0;
+    }
+
     /** The invoker's queue of units to be executed. */
     protected Queue _queue = new Queue();