[improve] [broker] Do not call cursor.isCursorDataFullyPersistable if disabled dispatcherPauseOnAckStatePersistentEnabled

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java

@@ -1087,6 +1087,15 @@ public void afterAckMessages(Throwable exOfDeletion, Object ctxOfDeletion) {
     @Override
     public boolean checkAndResumeIfPaused() {
         boolean paused = blockedDispatcherOnCursorDataCanNotFullyPersist == TRUE;
+        // Calling "cursor.isCursorDataFullyPersistable()" will loop the collection "individualDeletedMessages". It is
+        // not a light method.
+        // If never enabled "dispatcherPauseOnAckStatePersistentEnabled", skip the following checks to improve
+        // performance.
+        if (!paused && !topic.isDispatcherPauseOnAckStatePersistentEnabled()){
+            // "true" means no need to pause.
+            return true;
+        }
+        // Enabled "dispatcherPauseOnAckStatePersistentEnabled" before.
         boolean shouldPauseNow = !cursor.isCursorDataFullyPersistable()
                 && topic.isDispatcherPauseOnAckStatePersistentEnabled();
         // No need to change.

pulsar-broker/src/test/java/org/apache/pulsar/client/api/SubscriptionPauseOnAckStatPersistTest.java

@@ -23,8 +23,12 @@
 import java.util.Arrays;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.bookkeeper.mledger.Position;
+import org.apache.bookkeeper.mledger.impl.ManagedCursorContainer;
+import org.apache.bookkeeper.mledger.impl.ManagedCursorImpl;
+import org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl;
 import org.apache.pulsar.broker.BrokerTestUtil;
 import org.apache.pulsar.broker.service.Dispatcher;
 import org.apache.pulsar.broker.service.SystemTopicBasedTopicPoliciesService;
@@ -38,6 +42,7 @@
 import org.apache.pulsar.common.policies.data.TopicPolicies;
 import org.awaitility.Awaitility;
 import org.awaitility.reflect.WhiteboxImpl;
+import org.mockito.Mockito;
 import org.testng.Assert;
 import org.testng.annotations.AfterClass;
 import org.testng.annotations.BeforeClass;
@@ -549,4 +554,49 @@ public void testMultiConsumersPauseOnAckStatPersistNotAffectReplayRead(Subscript
         c4.close();
         admin.topics().delete(tpName, false);
     }
+
+    @Test(dataProvider = "multiConsumerSubscriptionTypes")
+    public void testNeverCallCursorIsCursorDataFullyPersistableIfDisabledTheFeature(SubscriptionType subscriptionType)
+            throws Exception {
+        final String tpName = BrokerTestUtil.newUniqueName("persistent://public/default/tp");
+        final String mlName = TopicName.get(tpName).getPersistenceNamingEncoding();
+        final String subscription = "s1";
+        final int msgSendCount = 100;
+        // Inject a injection to record the counter of calling "cursor.isCursorDataFullyPersistable".
+        final ManagedLedgerImpl ml = (ManagedLedgerImpl) pulsar.getBrokerService().getManagedLedgerFactory().open(mlName);
+        final ManagedCursorImpl cursor = (ManagedCursorImpl) ml.openCursor(subscription);
+        final ManagedCursorImpl spyCursor = Mockito.spy(cursor);
+        AtomicInteger callingIsCursorDataFullyPersistableCounter = new AtomicInteger();
+        Mockito.doAnswer(invocation -> {
+            callingIsCursorDataFullyPersistableCounter.incrementAndGet();
+            return invocation.callRealMethod();
+        }).when(spyCursor).isCursorDataFullyPersistable();
+        final ManagedCursorContainer cursors = WhiteboxImpl.getInternalState(ml, "cursors");
+        final ManagedCursorContainer activeCursors = WhiteboxImpl.getInternalState(ml, "activeCursors");
+        cursors.removeCursor(cursor.getName());
+        activeCursors.removeCursor(cursor.getName());
+        cursors.add(spyCursor, null);
+        activeCursors.add(spyCursor, null);
+
+        // Pub & Sub.
+        Consumer<String> c1 = pulsarClient.newConsumer(Schema.STRING).topic(tpName).subscriptionName(subscription)
+                .isAckReceiptEnabled(true).subscriptionType(subscriptionType).subscribe();
+        Producer<String> p1 = pulsarClient.newProducer(Schema.STRING).topic(tpName).enableBatching(false).create();
+        for (int i = 0; i < msgSendCount; i++) {
+            p1.send(Integer.valueOf(i).toString());
+        }
+        for (int i = 0; i < msgSendCount; i++) {
+            Message<String> m = c1.receive(2, TimeUnit.SECONDS);
+            Assert.assertNotNull(m);
+            c1.acknowledge(m);
+        }
+        // Verify: the counter of calling "cursor.isCursorDataFullyPersistable".
+        // In expected the counter should be "0", to avoid flaky, verify it is less than 5.
+        Assert.assertTrue(callingIsCursorDataFullyPersistableCounter.get() < 5);
+
+        // cleanup.
+        p1.close();
+        c1.close();
+        admin.topics().delete(tpName, false);
+    }
 }