fix: preserve hard-strict priority when the worker pool is busy

rqueue-core/src/main/java/com/github/sonus21/rqueue/listener/HardStrictPriorityPoller.java

@@ -208,7 +208,7 @@ void deactivate(int index, String queue, DeactivateType deactivateType) {
     if (deactivateType == DeactivateType.POLL_FAILED) {
       // Pause in case of connection errors or polling failures
       TimeoutUtils.sleepLog(backoffTime, false);
-    } else {
+    } else if (deactivateType == DeactivateType.NO_MESSAGE) {
       // Mark deactivation time if the queue is empty
       queueDeactivationTime.put(queue, System.currentTimeMillis());
     }

rqueue-core/src/test/java/com/github/sonus21/rqueue/listener/HardStrictPriorityPollerTest.java

@@ -1,19 +1,23 @@
 package com.github.sonus21.rqueue.listener;
 
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.lenient;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import com.github.sonus21.TestBase;
 import com.github.sonus21.rqueue.CoreUnitTest;
 import com.github.sonus21.rqueue.core.RqueueBeanProvider;
 import com.github.sonus21.rqueue.listener.RqueueMessageListenerContainer.QueueStateMgr;
+import com.github.sonus21.rqueue.listener.RqueueMessagePoller.DeactivateType;
 import com.github.sonus21.rqueue.utils.Constants;
 import com.github.sonus21.rqueue.utils.QueueThreadPool;
 import com.github.sonus21.rqueue.utils.TimeoutUtils;
@@ -67,7 +71,7 @@ public void setUp() {
         rqueueBeanProvider,
         queueStateMgr,
         Collections.emptyList(),
-        50L,
+        60_000L, // Keep deactivation from expiring during assertions.
         50L,
         postProcessingHandler,
         new MessageHeaders(Collections.emptyMap()),
@@ -109,6 +113,35 @@ void testExistMessagesInHigherPriorityQueueReturnsTrue() {
     assertTrue(result, "Should return true because high priority queue has messages");
   }
 
+  @Test
+  void testBusyPoolDoesNotHideHighPriorityMessages() throws Exception {
+    QueueThreadPool busyPool = mock(QueueThreadPool.class);
+    when(busyPool.acquire(1, poller.getSemaphoreWaitTime())).thenReturn(false);
+    lenient().doReturn(true).when(poller).existAvailableMessagesForPoll(highDetail);
+    lenient().doReturn(false).when(poller).existAvailableMessagesForPoll(lowDetail);
+
+    poller.poll(-1, highPriorityQueue, highDetail, busyPool);
+
+    verify(busyPool).acquire(1, poller.getSemaphoreWaitTime());
+    assertTrue(
+        poller.existMessagesInCurrentQueueOrHigherPriorityQueue(lowPriorityQueue, poller.queues),
+        "A busy pool must not hide pending high-priority messages");
+    verify(poller, never()).existAvailableMessagesForPoll(lowDetail);
+  }
+
+  @Test
+  void testEmptyQueueIsTemporarilySkipped() {
+    lenient().doReturn(false).when(poller).existAvailableMessagesForPoll(lowDetail);
+
+    poller.deactivate(-1, highPriorityQueue, DeactivateType.NO_MESSAGE);
+
+    assertFalse(
+        poller.existMessagesInCurrentQueueOrHigherPriorityQueue(lowPriorityQueue, poller.queues),
+        "An empty high-priority queue should remain inactive during the polling interval");
+    verify(poller, never()).existAvailableMessagesForPoll(highDetail);
+    verify(poller).existAvailableMessagesForPoll(lowDetail);
+  }
+
   @Test
   void testStrictExecutionPreventsLowPriorityPoll() throws Exception {
     AtomicInteger highQueuePollCount = new AtomicInteger(0);