OF-1028: Request ack only when unack'ed stanzas exist.

The peer might send unsollicited acks. Instead of requesting ack after every
so many stanzas that we send out, only request ack if we have unack'ed stanzas.

src/java/org/jivesoftware/openfire/streammanagement/StreamManager.java

@@ -57,12 +57,6 @@ public class StreamManager {
      */
     private String namespace;
 
-    /**
-     * Count of how many stanzas/packets
-     * have been sent from the server to the client (not necessarily processed)
-     */
-    private long serverSentStanzas = 0;
-
     /**
      * Count of how many stanzas/packets
      * sent from the client that the server has processed
@@ -229,15 +223,19 @@ public class StreamManager {
 	public void sentStanza(Packet packet) {
 
 		if(isEnabled()) {
-			synchronized (this) {
-				this.serverSentStanzas++;
+			final long requestFrequency = JiveGlobals.getLongProperty( "stream.management.requestFrequency", 5 );
+			final boolean requestAck;
 
+			synchronized (this) {
 				// The next ID is one higher than the last stanza that was sent (which might be unacknowledged!)
 				final long x = 1 + ( unacknowledgedServerStanzas.isEmpty() ? clientProcessedStanzas : unacknowledgedServerStanzas.getLast().x );
 				unacknowledgedServerStanzas.addLast( new StreamManager.UnackedPacket( x, packet.createCopy() ) );
-				Log.debug("Added stanza of type {} to collection of unacknowledged stanzas (x={}). Collection size is now {} / {}", packet.getElement().getName(), x, serverSentStanzas, unacknowledgedServerStanzas.size());
+
+				requestAck = unacknowledgedServerStanzas.size() >= requestFrequency;
+				Log.debug("Added stanza of type {} to collection of unacknowledged stanzas (x={}). Collection size is now {} / {}", packet.getElement().getName(), x, unacknowledgedServerStanzas.size());
 			}
-			if(serverSentStanzas % JiveGlobals.getLongProperty("stream.management.requestFrequency", 5) == 0) {
+
+			if(requestAck) {
 				sendServerRequest();
 			}
 		}