Fixes for shutdown sequence, including prevention of a race condition

* Throw an exception if any events, runnables or messages are posted after shutdown. These were previosuly being silently ignored. We really should know about them.
* Don't exit the connection manager thread until the object manager thread exits. This fixes a race condition where the wakeup time of the conmgr thread would determine if it shutdown before or after the object manager, meaning it would sometimes ignore messages around shutdown time.
* Add a shutdown constraint to make the client manager shutdown before the invoker/event/conmgr threads. This gives a single point in the shutdown sequence that applications can use as a constraint (TODO: shutdown groups?)
* Emit a log message for each shutdown method call. This could be very useful in production.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5491 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/server/PresentsDObjectMgr.java

@@ -201,6 +201,10 @@ public class PresentsDObjectMgr
     // from interface DObjectManager
     public void postEvent (DEvent event)
     {
+        if (!_running) {
+            throw new IllegalStateException("Object manager has been shutdown");
+        }
+
         // assign the event's id and append it to the queue
         event.eventId = getNextEventId(true);
         _evqueue.append(event);
@@ -273,6 +277,10 @@ public class PresentsDObjectMgr
      */
     public void postRunnable (Runnable unit)
     {
+        if (!_running) {
+            throw new IllegalStateException("Object manager has been shutdown");
+        }
+
         // just append it to the queue
         _evqueue.append(unit);
     }
@@ -563,6 +571,15 @@ public class PresentsDObjectMgr
         }
     }
 
+    /**
+     * Tests if the event processing thread is still running. This is required by the
+     * {@link ConnectionManager} to ensure messages posted just before or during shutdown are sent.
+     */
+    public synchronized boolean isRunning ()
+    {
+        return _running;
+    }
+
     /**
      * Processes a single unit from the queue.
      */
@@ -790,11 +807,6 @@ public class PresentsDObjectMgr
         }
     }
 
-    protected synchronized boolean isRunning ()
-    {
-        return _running;
-    }
-
     protected int getNextOid ()
     {
         // look for the next unused oid. in theory if we had two billion objects, this would loop