Check if unacknowledged stanzas queue is full before adding to it

to avoid an IllegalStateException.

Fixes SMACK-844.

smack-tcp/src/main/java/org/jivesoftware/smack/sm/StreamManagementException.java

@@ -16,10 +16,13 @@
  */
 package org.jivesoftware.smack.sm;
 
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.concurrent.BlockingQueue;
 
 import org.jivesoftware.smack.SmackException;
+import org.jivesoftware.smack.packet.Element;
 import org.jivesoftware.smack.packet.Stanza;
 
 public abstract class StreamManagementException extends SmackException {
@@ -110,5 +113,56 @@ public abstract class StreamManagementException extends SmackException {
             return ackedStanzas;
         }
     }
+
+    public static final class UnacknowledgedQueueFullException extends StreamManagementException {
+
+        /**
+         *
+         */
+        private static final long serialVersionUID = 1L;
+
+        private final int overflowElementNum;
+        private final int droppedElements;
+        private final List<Element> elements;
+        private final List<Stanza> unacknowledgesStanzas;
+
+        private UnacknowledgedQueueFullException(String message, int overflowElementNum, int droppedElements, List<Element> elements,
+                List<Stanza> unacknowledgesStanzas) {
+            super(message);
+            this.overflowElementNum = overflowElementNum;
+            this.droppedElements = droppedElements;
+            this.elements = elements;
+            this.unacknowledgesStanzas = unacknowledgesStanzas;
+        }
+
+        public int getOverflowElementNum() {
+            return overflowElementNum;
+        }
+
+        public int getDroppedElements() {
+            return droppedElements;
+        }
+
+        public List<Element> getElements() {
+            return elements;
+        }
+
+        public List<Stanza> getUnacknowledgesStanzas() {
+            return unacknowledgesStanzas;
+        }
+
+        public static UnacknowledgedQueueFullException newWith(int overflowElementNum, List<Element> elements,
+                BlockingQueue<Stanza> unacknowledgedStanzas) {
+            final int unacknowledgesStanzasQueueSize = unacknowledgedStanzas.size();
+            List<Stanza> localUnacknowledgesStanzas = new ArrayList<>(unacknowledgesStanzasQueueSize);
+            localUnacknowledgesStanzas.addAll(unacknowledgedStanzas);
+            int droppedElements = elements.size() - overflowElementNum - 1;
+
+            String message = "The queue size " + unacknowledgesStanzasQueueSize + " is not able to fit another "
+                    + droppedElements + " potential stanzas type top-level stream-elements.";
+            return new UnacknowledgedQueueFullException(message, overflowElementNum, droppedElements, elements,
+                    localUnacknowledgesStanzas);
+        }
+    }
 }
 

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java

@@ -1514,7 +1514,16 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
         private void drainWriterQueueToUnacknowledgedStanzas() {
             List<Element> elements = new ArrayList<>(queue.size());
             queue.drainTo(elements);
-            for (Element element : elements) {
+            for (int i = 0; i < elements.size(); i++) {
+                Element element = elements.get(i);
+                // If the unacknowledgedStanza queue is full, then bail out with a warning message. See SMACK-844.
+                if (unacknowledgedStanzas.remainingCapacity() == 0) {
+                    StreamManagementException.UnacknowledgedQueueFullException exception = StreamManagementException.UnacknowledgedQueueFullException
+                            .newWith(i, elements, unacknowledgedStanzas);
+                    LOGGER.log(Level.WARNING,
+                            "Some stanzas may be lost as not all could be drained to the unacknowledged stanzas queue", exception);
+                    return;
+                }
                 if (element instanceof Stanza) {
                     unacknowledgedStanzas.add((Stanza) element);
                 }