[ISSUE #10778] Skip empty priority queue groups

proxy/src/main/java/org/apache/rocketmq/proxy/service/route/MessageQueuePenalizer.java

@@ -120,15 +120,22 @@ static <Q extends MessageQueue> Pair<Q, Integer> selectLeastPenaltyWithPriority(
         int bestPenalty = Integer.MAX_VALUE;
         for (List<Q> queues : queuesWithPriority) {
             Pair<Q, Integer> queueAndPenalty = selectLeastPenalty(queues, penalizers, startIndex);
-            int penalty =  queueAndPenalty.getRight();
-            if (queueAndPenalty.getRight() <= 0) {
+            if (queueAndPenalty == null) {
+                continue;
+            }
+            int penalty = queueAndPenalty.getRight();
+            if (penalty <= 0) {
                 return queueAndPenalty;
             }
             if (penalty < bestPenalty) {
                 bestPenalty = penalty;
                 bestQueue = queueAndPenalty.getLeft();
             }
         }
-        return Pair.of(bestQueue,  bestPenalty);
+        if (bestQueue == null) {
+            // Every priority group was empty or contained no selectable queue.
+            return null;
+        }
+        return Pair.of(bestQueue, bestPenalty);
     }
-}
+}

proxy/src/test/java/org/apache/rocketmq/proxy/service/route/MessageQueuePenalizerTest.java

@@ -282,6 +282,40 @@ public void testSelectLeastPenaltyWithPriority_EmptyQueues() {
         assertNull(result);
     }
 
+    /**
+     * Test selectLeastPenaltyWithPriority with only empty priority groups should return null
+     */
+    @Test
+    public void testSelectLeastPenaltyWithPriority_AllEmptyPriorityGroups() {
+        List<MessageQueuePenalizer<MessageQueue>> penalizers = Collections.singletonList(mq -> 10);
+        AtomicInteger startIndex = new AtomicInteger(0);
+        Pair<MessageQueue, Integer> result = MessageQueuePenalizer.selectLeastPenaltyWithPriority(
+            Arrays.asList(Collections.emptyList(), Collections.emptyList()), penalizers, startIndex);
+        assertNull(result);
+    }
+
+    /**
+     * Test selectLeastPenaltyWithPriority skips empty priority groups and selects from non-empty groups
+     */
+    @Test
+    public void testSelectLeastPenaltyWithPriority_SkipEmptyPriorityGroup() {
+        MessageQueue mq0 = new MessageQueue("topic", "broker", 0);
+        MessageQueue mq1 = new MessageQueue("topic", "broker", 1);
+        List<MessageQueue> queues = Arrays.asList(mq0, mq1);
+
+        List<MessageQueuePenalizer<MessageQueue>> penalizers = Collections.singletonList(
+            mq -> mq.getQueueId() == 0 ? 20 : 10
+        );
+
+        AtomicInteger startIndex = new AtomicInteger(0);
+        Pair<MessageQueue, Integer> result = MessageQueuePenalizer.selectLeastPenaltyWithPriority(
+            Arrays.asList(Collections.emptyList(), queues), penalizers, startIndex);
+
+        assertNotNull(result);
+        assertEquals(mq1, result.getLeft());
+        assertEquals(10, result.getRight().intValue());
+    }
+
     /**
      * Test selectLeastPenaltyWithPriority with single priority group delegates to selectLeastPenalty
      */