fixing bug 723 by queuing Operations until initial load has completed

java/com.sap.sailing.server.replication.test/src/com/sap/sailing/server/replication/test/AbstractServerReplicationTest.java

@@ -52,7 +52,7 @@ public abstract class AbstractServerReplicationTest {
      */
     @Before
     public void setUp() throws Exception {
-        Pair<ReplicationService, ReplicationMasterDescriptor> result = basicSetUp(true, /* master=null means create a new one */ null,
+        Pair<ReplicationServiceTestImpl, ReplicationMasterDescriptor> result = basicSetUp(true, /* master=null means create a new one */ null,
                 /* replica=null means create a new one */ null);
         result.getA().startToReplicateFrom(result.getB());
     }
@@ -67,7 +67,7 @@ public abstract class AbstractServerReplicationTest {
      *            if not <code>null</code>, the value will be used for {@link #replica}; otherwise, a new racing event
      *            service will be created as replica
      */
-    protected Pair<ReplicationService, ReplicationMasterDescriptor> basicSetUp(
+    protected Pair<ReplicationServiceTestImpl, ReplicationMasterDescriptor> basicSetUp(
             boolean dropDB, RacingEventServiceImpl master, RacingEventServiceImpl replica) throws FileNotFoundException, Exception,
             JMSException, UnknownHostException {
         final MongoDBService mongoDBService = MongoDBService.INSTANCE;
@@ -132,9 +132,9 @@ public abstract class AbstractServerReplicationTest {
                 return null;
             }
         };
-        ReplicationService replicaReplicator = new ReplicationServiceTestImpl(resolveAgainst, rim, brokerMgr,
+        ReplicationServiceTestImpl replicaReplicator = new ReplicationServiceTestImpl(resolveAgainst, rim, brokerMgr,
                 replicaDescriptor, this.replica, this.master, masterReplicator);
-        Pair<ReplicationService, ReplicationMasterDescriptor> result = new Pair<>(replicaReplicator, masterDescriptor);
+        Pair<ReplicationServiceTestImpl, ReplicationMasterDescriptor> result = new Pair<>(replicaReplicator, masterDescriptor);
         return result;
     }
 
@@ -147,7 +147,7 @@ public abstract class AbstractServerReplicationTest {
         Activator.removeTemporaryTestBrokerPersistenceDirectory(brokerPersistenceDir);
     }
 
-    private static class ReplicationServiceTestImpl extends ReplicationServiceImpl {
+    static class ReplicationServiceTestImpl extends ReplicationServiceImpl {
         private final DomainFactory resolveAgainst;
         private final RacingEventService master;
         private final ReplicaDescriptor replicaDescriptor;
@@ -169,11 +169,19 @@ public abstract class AbstractServerReplicationTest {
         @Override
         public void startToReplicateFrom(ReplicationMasterDescriptor master) throws IOException,
                 ClassNotFoundException, JMSException {
+            Replicator replicator = startToReplicateFromButDontYetFetchInitialLoad(master, /* startReplicatorSuspended */ true);
+            initialLoad();
+            replicator.setSuspended(false); // resume after initial load
+        }
+
+        protected Replicator startToReplicateFromButDontYetFetchInitialLoad(ReplicationMasterDescriptor master, boolean startReplicatorSuspended)
+                throws JMSException, UnknownHostException {
             masterReplicationService.registerReplica(replicaDescriptor);
             registerReplicaUuidForMaster(replicaDescriptor.getUuid().toString(), master);
             TopicSubscriber replicationSubscription = master.getTopicSubscriber(replicaDescriptor.getUuid().toString());
-            replicationSubscription.setMessageListener(new Replicator(master, this));
-            initialLoad();
+            final Replicator replicator = new Replicator(master, this, startReplicatorSuspended);
+            replicationSubscription.setMessageListener(replicator);
+            return replicator;
         }
 
         /**
@@ -181,7 +189,7 @@ public abstract class AbstractServerReplicationTest {
          * {@link RacingEventServiceImpl#serializeForInitialReplication(ObjectOutputStream)} and
          * {@link RacingEventServiceImpl#initiallyFillFrom(ObjectInputStream)} through a piped input/output stream.
          */
-        private void initialLoad() throws IOException, ClassNotFoundException {
+        protected void initialLoad() throws IOException, ClassNotFoundException {
             PipedOutputStream pos = new PipedOutputStream();
             PipedInputStream pis = new PipedInputStream(pos);
             final ObjectOutputStream oos = new ObjectOutputStream(pos);

java/com.sap.sailing.server.replication.test/src/com/sap/sailing/server/replication/test/DelayedLeaderboardCorrectionsReplicationTest.java

@@ -99,7 +99,7 @@ public class DelayedLeaderboardCorrectionsReplicationTest extends AbstractServer
                 masterLeaderboardReloaded.getRaceColumnByName(Q2), MillisecondsTimePoint.now()));
 
         // replicate the re-loaded environment
-        Pair<ReplicationService, ReplicationMasterDescriptor> descriptors = basicSetUp(/* dropDB */ false, master, replica);
+        Pair<ReplicationServiceTestImpl, ReplicationMasterDescriptor> descriptors = basicSetUp(/* dropDB */ false, master, replica);
         replicaReplicator = descriptors.getA();
         masterDescriptor = descriptors.getB();
         replicaReplicator.startToReplicateFrom(masterDescriptor);

java/com.sap.sailing.server.replication/src/com/sap/sailing/server/replication/impl/ReplicationServiceImpl.java

@@ -179,11 +179,12 @@ public class ReplicationServiceImpl implements ReplicationService, OperationExec
         String uuid = registerReplicaWithMaster(master);
         TopicSubscriber replicationSubscription = master.getTopicSubscriber(uuid);
         URL initialLoadURL = master.getInitialLoadURL();
-        // TODO bug 723 hold back Replicator from performing operations received until initial load has completed
-        replicationSubscription.setMessageListener(new Replicator(master, this));
+        final Replicator replicator = new Replicator(master, this, /* startSuspended */ true);
+        replicationSubscription.setMessageListener(replicator);
         InputStream is = initialLoadURL.openStream();
         ObjectInputStream ois = new ObjectInputStream(is);
         getRacingEventService().initiallyFillFrom(ois);
+        replicator.setSuspended(false); // apply queued operations
     }
 
     /**

java/com.sap.sailing.server.replication/src/com/sap/sailing/server/replication/impl/Replicator.java

@@ -3,6 +3,9 @@ package com.sap.sailing.server.replication.impl;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
 
 import javax.jms.BytesMessage;
 import javax.jms.JMSException;
@@ -17,7 +20,12 @@ import com.sap.sailing.server.replication.ReplicationMasterDescriptor;
 /**
  * Receives {@link RacingEventServiceOperation}s through JMS and
  * {@link RacingEventService#apply(RacingEventServiceOperation) applies} them to the {@link RacingEventService} passed
- * to this replicator at construction.
+ * to this replicator at construction. When started in suspended mode, messages received will be turned into
+ * {@link RacingEventServiceOperation}s and then queued until {@link #setSuspended(boolean) setSuspended(false)} is invoked
+ * which applies all queued operations before applying the ones received later.<p>
+ * 
+ * The receiver takes care of synchronizing receiving, suspending/resuming and queuing. Waiters are notified
+ * whenever the result of {@link #isQueueEmpty} changes.
  * 
  * @author Axel Uhl (d043530)
  * 
@@ -25,10 +33,34 @@ import com.sap.sailing.server.replication.ReplicationMasterDescriptor;
 public class Replicator implements MessageListener {
     private final ReplicationMasterDescriptor master;
     private final HasRacingEventService racingEventServiceTracker;
+    private final List<RacingEventServiceOperation<?>> queue;
     
+    /**
+     * If the replicator is suspended, messages received are queued.
+     */
+    private boolean suspended;
+    
+    /**
+     * Starts the replicator immediately, not holding back messages received but forwarding them directly.
+     * 
+     * @param master
+     *            descriptor of the master server from which this replicator receives messages
+     * @param racingEventServiceTracker
+     *            OSGi service tracker for the replica to which to apply the messages received
+     */
     public Replicator(ReplicationMasterDescriptor master, HasRacingEventService racingEventServiceTracker) {
+        this(master, racingEventServiceTracker, /* startSuspended */ false);
+    }
+    
+    public Replicator(ReplicationMasterDescriptor master, HasRacingEventService racingEventServiceTracker, boolean startSuspended) {
+        this.queue = new ArrayList<RacingEventServiceOperation<?>>();
         this.master = master;
         this.racingEventServiceTracker = racingEventServiceTracker;
+        this.suspended = startSuspended;
+    }
+    
+    public synchronized boolean isQueueEmpty() {
+        return queue.isEmpty();
     }
 
     /**
@@ -37,7 +69,7 @@ public class Replicator implements MessageListener {
      * time.
      */
     @Override
-    public void onMessage(Message m) {
+    public synchronized void onMessage(Message m) {
         ClassLoader oldClassLoader = Thread.currentThread().getContextClassLoader();
         try {
             byte[] bytesFromMessage = getBytes((BytesMessage) m);
@@ -47,7 +79,7 @@ public class Replicator implements MessageListener {
             ObjectInputStream ois = DomainFactory.INSTANCE.createObjectInputStreamResolvingAgainstThisFactory(
                     new ByteArrayInputStream(bytesFromMessage));
             RacingEventServiceOperation<?> operation = (RacingEventServiceOperation<?>) ois.readObject();
-            racingEventServiceTracker.getRacingEventService().apply(operation);
+            applyOrQueue(operation);
         } catch (IOException | ClassNotFoundException | JMSException e) {
             throw new RuntimeException(e);
         } finally {
@@ -55,6 +87,53 @@ public class Replicator implements MessageListener {
         }
     }
 
+    /**
+     * If the replicator is currently {@link #suspended}, the <code>operation</code> is queued, otherwise immediately applied to
+     * the receiving replica.
+     */
+    private synchronized void applyOrQueue(RacingEventServiceOperation<?> operation) {
+        if (suspended) {
+            queue(operation);
+        } else {
+            apply(operation);
+        }
+    }
+
+    private synchronized void apply(RacingEventServiceOperation<?> operation) {
+        racingEventServiceTracker.getRacingEventService().apply(operation);
+    }
+    
+    private synchronized void queue(RacingEventServiceOperation<?> operation) {
+        if (queue.isEmpty()) {
+            notifyAll();
+        }
+        queue.add(operation);
+        assert !queue.isEmpty();
+    }
+    
+    public synchronized void setSuspended(final boolean suspended) {
+        if (this.suspended != suspended) {
+            this.suspended = suspended;
+            if (!this.suspended) {
+                applyQueue();
+            }
+        }
+    }
+    
+    private synchronized void applyQueue() {
+        for (Iterator<RacingEventServiceOperation<?>> i=queue.iterator(); i.hasNext(); ) {
+            RacingEventServiceOperation<?> operation = i.next();
+            i.remove();
+            apply(operation);
+        }
+        assert queue.isEmpty();
+        notifyAll();
+    }
+
+    public synchronized boolean isSuspended() {
+        return suspended;
+    }
+
     private byte[] getBytes(BytesMessage m) throws JMSException {
         byte[] buf = new byte[(int) m.getBodyLength()];
         m.readBytes(buf);
@@ -63,7 +142,7 @@ public class Replicator implements MessageListener {
 
     @Override
     public String toString() {
-        return "Replicator for master "+master;
+        return "Replicator for master "+master+", queue size: "+queue.size();
     }
 
 }

java/com.sap.sailing.server/src/com/sap/sailing/server/operationaltransformation/CreateFlexibleLeaderboard.java

@@ -1,10 +1,13 @@
 package com.sap.sailing.server.operationaltransformation;
 
+import java.util.logging.Logger;
+
 import com.sap.sailing.domain.leaderboard.FlexibleLeaderboard;
 import com.sap.sailing.server.RacingEventService;
 import com.sap.sailing.server.RacingEventServiceOperation;
 
 public class CreateFlexibleLeaderboard extends AbstractLeaderboardOperation<FlexibleLeaderboard> {
+    private static final Logger logger = Logger.getLogger(CreateFlexibleLeaderboard.class.getName());
     private static final long serialVersionUID = 891352705068098580L;
     private final int[] discardThresholds;
 
@@ -15,7 +18,13 @@ public class CreateFlexibleLeaderboard extends AbstractLeaderboardOperation<Flex
 
     @Override
     public FlexibleLeaderboard internalApplyTo(RacingEventService toState) {
-        return toState.addFlexibleLeaderboard(getLeaderboardName(), discardThresholds);
+        FlexibleLeaderboard result = null;
+        if (toState.getLeaderboardByName(getLeaderboardName()) == null) {
+            result = toState.addFlexibleLeaderboard(getLeaderboardName(), discardThresholds);
+        } else {
+            logger.warning("Cannot replicate creation of flexible leaderboard "+getLeaderboardName()+" because it already exists in the replica");
+        }
+        return result;
     }
 
     @Override