AMQ-6642: Fix potential NPE on updateMessage

Fixing potential NPE when calling updateMessage on a Queue store in
KahaDB if subscription statistics are enabled.  Also reduced the
visibily from public to protected to subscription statistic related
methods that shouldn't be public and added null pointer checks there as
well.

https://issues.apache.org/jira/browse/AMQ-6642

activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/MessageDatabase.java

@@ -1524,7 +1524,7 @@ public abstract class MessageDatabase extends ServiceSupport implements BrokerSe
                 decrementAndSubSizeToStoreStat(command.getDestination(), previousKeys.location.getSize());
 
                 //update all the subscription metrics
-                if (enableSubscriptionStatistics && location.getSize() != previousKeys.location.getSize()) {
+                if (enableSubscriptionStatistics && sd.ackPositions != null && location.getSize() != previousKeys.location.getSize()) {
                     Iterator<Entry<String, SequenceSet>> iter = sd.ackPositions.iterator(tx);
                     while (iter.hasNext()) {
                         Entry<String, SequenceSet> e = iter.next();
@@ -2970,22 +2970,26 @@ public abstract class MessageDatabase extends ServiceSupport implements BrokerSe
         return sd.subscriptionAcks.get(tx, subscriptionKey);
     }
 
-    public long getStoredMessageCount(Transaction tx, StoredDestination sd, String subscriptionKey) throws IOException {
+    protected long getStoredMessageCount(Transaction tx, StoredDestination sd, String subscriptionKey) throws IOException {
+        if (sd.ackPositions != null) {
             SequenceSet messageSequences = sd.ackPositions.get(tx, subscriptionKey);
             if (messageSequences != null) {
                 long result = messageSequences.rangeSize();
                 // if there's anything in the range the last value is always the nextMessage marker, so remove 1.
                 return result > 0 ? result - 1 : 0;
             }
+        }
 
         return 0;
     }
 
-    public long getStoredMessageSize(Transaction tx, StoredDestination sd, String subscriptionKey) throws IOException {
+    protected long getStoredMessageSize(Transaction tx, StoredDestination sd, String subscriptionKey) throws IOException {
+        long locationSize = 0;
+
+        if (sd.ackPositions != null) {
             //grab the messages attached to this subscription
             SequenceSet messageSequences = sd.ackPositions.get(tx, subscriptionKey);
 
-        long locationSize = 0;
             if (messageSequences != null) {
                 Sequence head = messageSequences.getHead();
                 if (head != null) {
@@ -3000,6 +3004,7 @@ public abstract class MessageDatabase extends ServiceSupport implements BrokerSe
                     }
                 }
             }
+        }
 
         return locationSize;
     }

activemq-kahadb-store/src/test/java/org/apache/activemq/store/kahadb/MessageDatabaseSizeTest.java

@@ -17,9 +17,12 @@
 package org.apache.activemq.store.kahadb;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
 
 import org.apache.activemq.broker.BrokerService;
 import org.apache.activemq.command.ActiveMQQueue;
@@ -36,13 +39,27 @@ import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@RunWith(Parameterized.class)
 public class MessageDatabaseSizeTest {
 
     private static final Logger LOG = LoggerFactory.getLogger(MessageDatabaseSizeTest.class);
 
+    @Parameters(name = "subStatsEnabled={0}")
+    public static Collection<Object[]> data() {
+        return Arrays.asList(new Object[][] {
+                // Subscription stats on
+                {true},
+                // Subscription stats off
+                {false}
+        });
+    }
+
     @Rule
     public TemporaryFolder dataDir = new TemporaryFolder(new File("target"));
     private final String payload = new String(new byte[1024]);
@@ -50,6 +67,13 @@ public class MessageDatabaseSizeTest {
     private BrokerService broker = null;
     private final ActiveMQQueue destination = new ActiveMQQueue("Test");
     private KahaDBPersistenceAdapter adapter;
+    private boolean subStatsEnabled;
+
+    public MessageDatabaseSizeTest(boolean subStatsEnabled) {
+        super();
+        this.subStatsEnabled = subStatsEnabled;
+    }
+
 
     protected void startBroker() throws Exception {
         broker = new BrokerService();
@@ -58,6 +82,7 @@ public class MessageDatabaseSizeTest {
         broker.setUseJmx(true);
         broker.setDataDirectory(dataDir.getRoot().getAbsolutePath());
         adapter = (KahaDBPersistenceAdapter) broker.getPersistenceAdapter();
+        adapter.setEnableSubscriptionStatistics(subStatsEnabled);
         broker.start();
         LOG.info("Starting broker..");
     }
@@ -101,6 +126,22 @@ public class MessageDatabaseSizeTest {
         assertEquals(existingSize, messageStore.getMessageSize());
     }
 
+    @Test
+    public void testUpdateMessageSameLocationDifferentSize() throws Exception {
+        final KahaDBStore store = adapter.getStore();
+        MessageId messageId = new MessageId("111:222:333");
+        ActiveMQTextMessage textMessage = getMessage(new MessageId("111:222:333"));
+
+        //Add a single message and update once so we can compare the size consistently
+        MessageStore messageStore = store.createQueueMessageStore(destination);
+        messageStore.addMessage(broker.getAdminConnectionContext(), textMessage);
+        textMessage.setText("new size of message");
+        messageStore.updateMessage(textMessage);
+
+        assertNotNull(findMessageLocation(messageId.toString(), store.convert(destination)));
+
+    }
+
     /**
      * Test that when updating an existing message to a different location in the
      * journal that the index size doesn't change