Enabled overriding of subscription from same client to same topic with different QoS, the latest wins

broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/HawtDBStorageService.java

@@ -225,6 +225,17 @@ public class HawtDBStorageService implements IStorageService {
         Set<Subscription> subs = m_persistentSubscriptions.get(clientID);
         if (!subs.contains(newSubscription)) {
             LOG.debug("updating clientID {} subscriptions set with new subscription", clientID);
+            //TODO check the subs doesn't contain another subscription to the same topic with different
+            Subscription existingSubscription = null;
+            for (Subscription scanSub : subs) {
+                if (newSubscription.getTopic().equals(scanSub.getTopic())) {
+                    existingSubscription = scanSub;
+                    break;
+                }
+            }
+            if (existingSubscription != null) {
+                subs.remove(existingSubscription);
+            }
             subs.add(newSubscription);
             m_persistentSubscriptions.put(clientID, subs);
             LOG.debug("clientID {} subscriptions set now is {}", clientID, subs);

broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/subscriptions/TreeNode.java

@@ -1,11 +1,21 @@
 package org.dna.mqtt.moquette.messaging.spi.impl.subscriptions;
 
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Queue;
 import java.util.concurrent.LinkedBlockingQueue;
 
 class TreeNode {
+    
+    private class ClientIDComparator implements Comparator<Subscription> {
+
+        public int compare(Subscription o1, Subscription o2) {
+            return o1.getClientId().compareTo(o2.getClientId());
+        }
+        
+    }
 
     TreeNode m_parent;
     Token m_token;
@@ -25,10 +35,16 @@ class TreeNode {
     }
 
     void addSubscription(Subscription s) {
-        //avoid double registering
+        //avoid double registering for same clientID, topic and QoS
         if (m_subscriptions.contains(s)) {
             return;
         }
+        //remove existing subscription for same client and topic but different QoS
+        int existingSubIdx = Collections.binarySearch(m_subscriptions, s, new ClientIDComparator());
+        if (existingSubIdx >= 0) {
+            m_subscriptions.remove(existingSubIdx);
+        }
+        
         m_subscriptions.add(s);
     }