Refactor TransactionProxy
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / TransactionProxy.java
index 9f48ef96cf517e265970b744b87af014dc51cbca..5bc53442aeff04aa43c299a49890b3ecfe70b974 100644 (file)
@@ -18,9 +18,9 @@ import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import com.google.common.util.concurrent.CheckedFuture;
-import com.google.common.util.concurrent.FutureCallback;
-import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.SettableFuture;
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -35,17 +35,6 @@ import org.opendaylight.controller.cluster.datastore.identifiers.TransactionIden
 import org.opendaylight.controller.cluster.datastore.messages.CloseTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
-import org.opendaylight.controller.cluster.datastore.messages.DataExists;
-import org.opendaylight.controller.cluster.datastore.messages.DataExistsReply;
-import org.opendaylight.controller.cluster.datastore.messages.DeleteData;
-import org.opendaylight.controller.cluster.datastore.messages.MergeData;
-import org.opendaylight.controller.cluster.datastore.messages.ReadData;
-import org.opendaylight.controller.cluster.datastore.messages.ReadDataReply;
-import org.opendaylight.controller.cluster.datastore.messages.ReadyTransaction;
-import org.opendaylight.controller.cluster.datastore.messages.ReadyTransactionReply;
-import org.opendaylight.controller.cluster.datastore.messages.SerializableMessage;
-import org.opendaylight.controller.cluster.datastore.messages.VersionedSerializableMessage;
-import org.opendaylight.controller.cluster.datastore.messages.WriteData;
 import org.opendaylight.controller.cluster.datastore.shardstrategy.ShardStrategyFactory;
 import org.opendaylight.controller.cluster.datastore.utils.ActorContext;
 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
@@ -266,14 +255,17 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
 
         throttleOperation();
 
+        final SettableFuture<Optional<NormalizedNode<?, ?>>> proxyFuture = SettableFuture.create();
+
         TransactionFutureCallback txFutureCallback = getOrCreateTxFutureCallback(path);
-        return txFutureCallback.enqueueReadOperation(new ReadOperation<Optional<NormalizedNode<?, ?>>>() {
+        txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
             @Override
-            public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> invoke(
-                    TransactionContext transactionContext) {
-                return transactionContext.readData(path);
+            public void invoke(TransactionContext transactionContext) {
+                transactionContext.readData(path, proxyFuture);
             }
         });
+
+        return MappingCheckedFuture.create(proxyFuture, ReadFailedException.MAPPER);
     }
 
     @Override
@@ -286,15 +278,18 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
 
         throttleOperation();
 
+        final SettableFuture<Boolean> proxyFuture = SettableFuture.create();
+
         TransactionFutureCallback txFutureCallback = getOrCreateTxFutureCallback(path);
-        return txFutureCallback.enqueueReadOperation(new ReadOperation<Boolean>() {
+        txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
             @Override
-            public CheckedFuture<Boolean, ReadFailedException> invoke(TransactionContext transactionContext) {
-                return transactionContext.dataExists(path);
+            public void invoke(TransactionContext transactionContext) {
+                transactionContext.dataExists(path, proxyFuture);
             }
         });
-    }
 
+        return MappingCheckedFuture.create(proxyFuture, ReadFailedException.MAPPER);
+    }
 
     private void checkModificationState() {
         Preconditions.checkState(transactionType != TransactionType.READ_ONLY,
@@ -332,7 +327,7 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
         throttleOperation();
 
         TransactionFutureCallback txFutureCallback = getOrCreateTxFutureCallback(path);
-        txFutureCallback.enqueueModifyOperation(new TransactionOperation() {
+        txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
             @Override
             public void invoke(TransactionContext transactionContext) {
                 transactionContext.writeData(path, data);
@@ -350,7 +345,7 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
         throttleOperation();
 
         TransactionFutureCallback txFutureCallback = getOrCreateTxFutureCallback(path);
-        txFutureCallback.enqueueModifyOperation(new TransactionOperation() {
+        txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
             @Override
             public void invoke(TransactionContext transactionContext) {
                 transactionContext.mergeData(path, data);
@@ -368,7 +363,7 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
         throttleOperation();
 
         TransactionFutureCallback txFutureCallback = getOrCreateTxFutureCallback(path);
-        txFutureCallback.enqueueModifyOperation(new TransactionOperation() {
+        txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
             @Override
             public void invoke(TransactionContext transactionContext) {
                 transactionContext.deleteData(path);
@@ -395,12 +390,21 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
             LOG.debug("Tx {} Readying transaction for shard {} chain {}", identifier,
                         txFutureCallback.getShardName(), transactionChainId);
 
-            Future<ActorSelection> future = txFutureCallback.enqueueFutureOperation(new FutureOperation<ActorSelection>() {
-                @Override
-                public Future<ActorSelection> invoke(TransactionContext transactionContext) {
-                    return transactionContext.readyTransaction();
-                }
-            });
+            final TransactionContext transactionContext = txFutureCallback.getTransactionContext();
+            final Future<ActorSelection> future;
+            if (transactionContext != null) {
+                // avoid the creation of a promise and a TransactionOperation
+                future = transactionContext.readyTransaction();
+            } else {
+                final Promise<ActorSelection> promise = akka.dispatch.Futures.promise();
+                txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
+                    @Override
+                    public void invoke(TransactionContext transactionContext) {
+                        promise.completeWith(transactionContext.readyTransaction());
+                    }
+                });
+                future = promise.future();
+            }
 
             cohortFutures.add(future);
         }
@@ -439,7 +443,7 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
     @Override
     public void close() {
         for (TransactionFutureCallback txFutureCallback : txFutureCallbackMap.values()) {
-            txFutureCallback.enqueueModifyOperation(new TransactionOperation() {
+            txFutureCallback.enqueueTransactionOperation(new TransactionOperation() {
                 @Override
                 public void invoke(TransactionContext transactionContext) {
                     transactionContext.closeTransaction();
@@ -501,20 +505,6 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
         void invoke(TransactionContext transactionContext);
     }
 
-    /**
-     * This interface returns a Guava Future
-     */
-    private static interface ReadOperation<T> {
-        CheckedFuture<T, ReadFailedException> invoke(TransactionContext transactionContext);
-    }
-
-    /**
-     * This interface returns a Scala Future
-     */
-    private static interface FutureOperation<T> {
-        Future<T> invoke(TransactionContext transactionContext);
-    }
-
     /**
      * Implements a Future OnComplete callback for a CreateTransaction message. This class handles
      * retries, up to a limit, if the shard doesn't have a leader yet. This is done by scheduling a
@@ -576,75 +566,22 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
          * Adds a TransactionOperation to be executed after the CreateTransaction completes.
          */
         void addTxOperationOnComplete(TransactionOperation operation) {
+            boolean invokeOperation = true;
             synchronized(txOperationsOnComplete) {
                 if(transactionContext == null) {
                     LOG.debug("Tx {} Adding operation on complete {}", identifier);
 
+                    invokeOperation = false;
                     txOperationsOnComplete.add(operation);
-                } else {
-                    operation.invoke(transactionContext);
                 }
             }
-        }
-
-
-        <T> Future<T> enqueueFutureOperation(final FutureOperation<T> op) {
-
-            Future<T> future;
-
-            if (transactionContext != null) {
-                future = op.invoke(transactionContext);
-            } else {
-                // The shard Tx hasn't been created yet so add the Tx operation to the Tx Future
-                // callback to be executed after the Tx is created.
-                final Promise<T> promise = akka.dispatch.Futures.promise();
-                addTxOperationOnComplete(new TransactionOperation() {
-                    @Override
-                    public void invoke(TransactionContext transactionContext) {
-                        promise.completeWith(op.invoke(transactionContext));
-                    }
-                });
-
-                future = promise.future();
-            }
-
-            return future;
-        }
-
-        <T> CheckedFuture<T, ReadFailedException> enqueueReadOperation(final ReadOperation<T> op) {
-
-            CheckedFuture<T, ReadFailedException> future;
-
-            if (transactionContext != null) {
-                future = op.invoke(transactionContext);
-            } else {
-                // The shard Tx hasn't been created yet so add the Tx operation to the Tx Future
-                // callback to be executed after the Tx is created.
-                final SettableFuture<T> proxyFuture = SettableFuture.create();
-                addTxOperationOnComplete(new TransactionOperation() {
-                    @Override
-                    public void invoke(TransactionContext transactionContext) {
-                        Futures.addCallback(op.invoke(transactionContext), new FutureCallback<T>() {
-                            @Override
-                            public void onSuccess(T data) {
-                                proxyFuture.set(data);
-                            }
-
-                            @Override
-                            public void onFailure(Throwable t) {
-                                proxyFuture.setException(t);
-                            }
-                        });
-                    }
-                });
 
-                future = MappingCheckedFuture.create(proxyFuture, ReadFailedException.MAPPER);
+            if(invokeOperation) {
+                operation.invoke(transactionContext);
             }
-
-            return future;
         }
 
-        void enqueueModifyOperation(final TransactionOperation op) {
+        void enqueueTransactionOperation(final TransactionOperation op) {
 
             if (transactionContext != null) {
                 op.invoke(transactionContext);
@@ -689,43 +626,63 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
                 }
             }
 
-            // Create the TransactionContext from the response or failure and execute delayed
-            // TransactionOperations. This entire section is done atomically (ie synchronized) with
-            // respect to #addTxOperationOnComplete to handle timing issues and ensure no
-            // TransactionOperation is missed and that they are processed in the order they occurred.
-            synchronized(txOperationsOnComplete) {
-                // Store the new TransactionContext locally until we've completed invoking the
-                // TransactionOperations. This avoids thread timing issues which could cause
-                // out-of-order TransactionOperations. Eg, on a modification operation, if the
-                // TransactionContext is non-null, then we directly call the TransactionContext.
-                // However, at the same time, the code may be executing the cached
-                // TransactionOperations. So to avoid thus timing, we don't publish the
-                // TransactionContext until after we've executed all cached TransactionOperations.
-                TransactionContext localTransactionContext;
-                if(failure != null) {
-                    LOG.debug("Tx {} Creating NoOpTransaction because of error: {}", identifier,
-                            failure.getMessage());
-
-                    localTransactionContext = new NoOpTransactionContext(failure, identifier, operationLimiter);
-                } else if (response.getClass().equals(CreateTransactionReply.SERIALIZABLE_CLASS)) {
-                    localTransactionContext = createValidTransactionContext(
-                            CreateTransactionReply.fromSerializable(response));
-                } else {
-                    IllegalArgumentException exception = new IllegalArgumentException(String.format(
+            // Create the TransactionContext from the response or failure. Store the new
+            // TransactionContext locally until we've completed invoking the
+            // TransactionOperations. This avoids thread timing issues which could cause
+            // out-of-order TransactionOperations. Eg, on a modification operation, if the
+            // TransactionContext is non-null, then we directly call the TransactionContext.
+            // However, at the same time, the code may be executing the cached
+            // TransactionOperations. So to avoid thus timing, we don't publish the
+            // TransactionContext until after we've executed all cached TransactionOperations.
+            TransactionContext localTransactionContext;
+            if(failure != null) {
+                LOG.debug("Tx {} Creating NoOpTransaction because of error: {}", identifier,
+                        failure.getMessage());
+
+                localTransactionContext = new NoOpTransactionContext(failure, identifier, operationLimiter);
+            } else if (response.getClass().equals(CreateTransactionReply.SERIALIZABLE_CLASS)) {
+                localTransactionContext = createValidTransactionContext(
+                        CreateTransactionReply.fromSerializable(response));
+            } else {
+                IllegalArgumentException exception = new IllegalArgumentException(String.format(
                         "Invalid reply type %s for CreateTransaction", response.getClass()));
 
-                    localTransactionContext = new NoOpTransactionContext(exception, identifier, operationLimiter);
+                localTransactionContext = new NoOpTransactionContext(exception, identifier, operationLimiter);
+            }
+
+            executeTxOperatonsOnComplete(localTransactionContext);
+        }
+
+        private void executeTxOperatonsOnComplete(TransactionContext localTransactionContext) {
+            while(true) {
+                // Access to txOperationsOnComplete and transactionContext must be protected and atomic
+                // (ie synchronized) with respect to #addTxOperationOnComplete to handle timing
+                // issues and ensure no TransactionOperation is missed and that they are processed
+                // in the order they occurred.
+
+                // We'll make a local copy of the txOperationsOnComplete list to handle re-entrancy
+                // in case a TransactionOperation results in another transaction operation being
+                // queued (eg a put operation from a client read Future callback that is notified
+                // synchronously).
+                Collection<TransactionOperation> operationsBatch = null;
+                synchronized(txOperationsOnComplete) {
+                    if(txOperationsOnComplete.isEmpty()) {
+                        // We're done invoking the TransactionOperations so we can now publish the
+                        // TransactionContext.
+                        transactionContext = localTransactionContext;
+                        break;
+                    }
+
+                    operationsBatch = new ArrayList<>(txOperationsOnComplete);
+                    txOperationsOnComplete.clear();
                 }
 
-                for(TransactionOperation oper: txOperationsOnComplete) {
+                // Invoke TransactionOperations outside the sync block to avoid unnecessary blocking.
+                // A slight down-side is that we need to re-acquire the lock below but this should
+                // be negligible.
+                for(TransactionOperation oper: operationsBatch) {
                     oper.invoke(localTransactionContext);
                 }
-
-                txOperationsOnComplete.clear();
-
-                // We're done invoking the TransactionOperations so we can now publish the
-                // TransactionContext.
-                transactionContext = localTransactionContext;
             }
         }
 
@@ -754,420 +711,4 @@ public class TransactionProxy implements DOMStoreReadWriteTransaction {
                 actorContext, schemaContext, isTxActorLocal, reply.getVersion(), operationCompleter);
         }
     }
-
-    private interface TransactionContext {
-        void closeTransaction();
-
-        Future<ActorSelection> readyTransaction();
-
-        void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
-
-        void deleteData(YangInstanceIdentifier path);
-
-        void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
-
-        CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
-                final YangInstanceIdentifier path);
-
-        CheckedFuture<Boolean, ReadFailedException> dataExists(YangInstanceIdentifier path);
-
-        List<Future<Object>> getRecordedOperationFutures();
-    }
-
-    private static abstract class AbstractTransactionContext implements TransactionContext {
-
-        protected final TransactionIdentifier identifier;
-        protected final List<Future<Object>> recordedOperationFutures = Lists.newArrayList();
-
-        AbstractTransactionContext(TransactionIdentifier identifier) {
-            this.identifier = identifier;
-        }
-
-        @Override
-        public List<Future<Object>> getRecordedOperationFutures() {
-            return recordedOperationFutures;
-        }
-    }
-
-    private static class TransactionContextImpl extends AbstractTransactionContext {
-        private final Logger LOG = LoggerFactory.getLogger(TransactionContextImpl.class);
-
-        private final ActorContext actorContext;
-        private final String transactionPath;
-        private final ActorSelection actor;
-        private final boolean isTxActorLocal;
-        private final short remoteTransactionVersion;
-        private final OperationCompleter operationCompleter;
-
-
-        private TransactionContextImpl(String transactionPath, ActorSelection actor, TransactionIdentifier identifier,
-                ActorContext actorContext, SchemaContext schemaContext,
-                boolean isTxActorLocal, short remoteTransactionVersion, OperationCompleter operationCompleter) {
-            super(identifier);
-            this.transactionPath = transactionPath;
-            this.actor = actor;
-            this.actorContext = actorContext;
-            this.isTxActorLocal = isTxActorLocal;
-            this.remoteTransactionVersion = remoteTransactionVersion;
-            this.operationCompleter = operationCompleter;
-        }
-
-        private Future<Object> completeOperation(Future<Object> operationFuture){
-            operationFuture.onComplete(this.operationCompleter, actorContext.getActorSystem().dispatcher());
-            return operationFuture;
-        }
-
-
-        private ActorSelection getActor() {
-            return actor;
-        }
-
-        private Future<Object> executeOperationAsync(SerializableMessage msg) {
-            return completeOperation(actorContext.executeOperationAsync(getActor(), isTxActorLocal ? msg : msg.toSerializable()));
-        }
-
-        private Future<Object> executeOperationAsync(VersionedSerializableMessage msg) {
-            return completeOperation(actorContext.executeOperationAsync(getActor(), isTxActorLocal ? msg :
-                    msg.toSerializable(remoteTransactionVersion)));
-        }
-
-        @Override
-        public void closeTransaction() {
-            LOG.debug("Tx {} closeTransaction called", identifier);
-
-            actorContext.sendOperationAsync(getActor(), CloseTransaction.INSTANCE.toSerializable());
-        }
-
-        @Override
-        public Future<ActorSelection> readyTransaction() {
-            LOG.debug("Tx {} readyTransaction called with {} previous recorded operations pending",
-                    identifier, recordedOperationFutures.size());
-
-            // Send the ReadyTransaction message to the Tx actor.
-
-            final Future<Object> replyFuture = executeOperationAsync(ReadyTransaction.INSTANCE);
-
-            // Combine all the previously recorded put/merge/delete operation reply Futures and the
-            // ReadyTransactionReply Future into one Future. If any one fails then the combined
-            // Future will fail. We need all prior operations and the ready operation to succeed
-            // in order to attempt commit.
-
-            List<Future<Object>> futureList =
-                    Lists.newArrayListWithCapacity(recordedOperationFutures.size() + 1);
-            futureList.addAll(recordedOperationFutures);
-            futureList.add(replyFuture);
-
-            Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(futureList,
-                    actorContext.getActorSystem().dispatcher());
-
-            // Transform the combined Future into a Future that returns the cohort actor path from
-            // the ReadyTransactionReply. That's the end result of the ready operation.
-
-            return combinedFutures.transform(new Mapper<Iterable<Object>, ActorSelection>() {
-                @Override
-                public ActorSelection checkedApply(Iterable<Object> notUsed) {
-                    LOG.debug("Tx {} readyTransaction: pending recorded operations succeeded",
-                            identifier);
-
-                    // At this point all the Futures succeeded and we need to extract the cohort
-                    // actor path from the ReadyTransactionReply. For the recorded operations, they
-                    // don't return any data so we're only interested that they completed
-                    // successfully. We could be paranoid and verify the correct reply types but
-                    // that really should never happen so it's not worth the overhead of
-                    // de-serializing each reply.
-
-                    // Note the Future get call here won't block as it's complete.
-                    Object serializedReadyReply = replyFuture.value().get().get();
-                    if (serializedReadyReply instanceof ReadyTransactionReply) {
-                        return actorContext.actorSelection(((ReadyTransactionReply)serializedReadyReply).getCohortPath());
-
-                    } else if(serializedReadyReply.getClass().equals(ReadyTransactionReply.SERIALIZABLE_CLASS)) {
-                        ReadyTransactionReply reply = ReadyTransactionReply.fromSerializable(serializedReadyReply);
-                        String cohortPath = reply.getCohortPath();
-
-                        // In Helium we used to return the local path of the actor which represented
-                        // a remote ThreePhaseCommitCohort. The local path would then be converted to
-                        // a remote path using this resolvePath method. To maintain compatibility with
-                        // a Helium node we need to continue to do this conversion.
-                        // At some point in the future when upgrades from Helium are not supported
-                        // we could remove this code to resolvePath and just use the cohortPath as the
-                        // resolved cohortPath
-                        if(TransactionContextImpl.this.remoteTransactionVersion <
-                                DataStoreVersions.HELIUM_1_VERSION) {
-                            cohortPath = actorContext.resolvePath(transactionPath, cohortPath);
-                        }
-
-                        return actorContext.actorSelection(cohortPath);
-
-                    } else {
-                        // Throwing an exception here will fail the Future.
-                        throw new IllegalArgumentException(String.format("Invalid reply type {}",
-                                serializedReadyReply.getClass()));
-                    }
-                }
-            }, SAME_FAILURE_TRANSFORMER, actorContext.getActorSystem().dispatcher());
-        }
-
-        @Override
-        public void deleteData(YangInstanceIdentifier path) {
-            LOG.debug("Tx {} deleteData called path = {}", identifier, path);
-
-            recordedOperationFutures.add(executeOperationAsync(new DeleteData(path)));
-        }
-
-        @Override
-        public void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
-            LOG.debug("Tx {} mergeData called path = {}", identifier, path);
-
-            recordedOperationFutures.add(executeOperationAsync(new MergeData(path, data)));
-        }
-
-        @Override
-        public void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
-            LOG.debug("Tx {} writeData called path = {}", identifier, path);
-
-            recordedOperationFutures.add(executeOperationAsync(new WriteData(path, data)));
-        }
-
-        @Override
-        public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
-                final YangInstanceIdentifier path) {
-
-            LOG.debug("Tx {} readData called path = {}", identifier, path);
-
-            final SettableFuture<Optional<NormalizedNode<?, ?>>> returnFuture = SettableFuture.create();
-
-            // If there were any previous recorded put/merge/delete operation reply Futures then we
-            // must wait for them to successfully complete. This is necessary to honor the read
-            // uncommitted semantics of the public API contract. If any one fails then fail the read.
-
-            if(recordedOperationFutures.isEmpty()) {
-                finishReadData(path, returnFuture);
-            } else {
-                LOG.debug("Tx {} readData: verifying {} previous recorded operations",
-                        identifier, recordedOperationFutures.size());
-
-                // Note: we make a copy of recordedOperationFutures to be on the safe side in case
-                // Futures#sequence accesses the passed List on a different thread, as
-                // recordedOperationFutures is not synchronized.
-
-                Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(
-                        Lists.newArrayList(recordedOperationFutures),
-                        actorContext.getActorSystem().dispatcher());
-
-                OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
-                    @Override
-                    public void onComplete(Throwable failure, Iterable<Object> notUsed)
-                            throws Throwable {
-                        if(failure != null) {
-                            LOG.debug("Tx {} readData: a recorded operation failed: {}",
-                                    identifier, failure);
-                            returnFuture.setException(new ReadFailedException(
-                                    "The read could not be performed because a previous put, merge,"
-                                    + "or delete operation failed", failure));
-                        } else {
-                            finishReadData(path, returnFuture);
-                        }
-                    }
-                };
-
-                combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
-            }
-
-            return MappingCheckedFuture.create(returnFuture, ReadFailedException.MAPPER);
-        }
-
-        private void finishReadData(final YangInstanceIdentifier path,
-                final SettableFuture<Optional<NormalizedNode<?, ?>>> returnFuture) {
-
-            LOG.debug("Tx {} finishReadData called path = {}", identifier, path);
-
-            OnComplete<Object> onComplete = new OnComplete<Object>() {
-                @Override
-                public void onComplete(Throwable failure, Object readResponse) throws Throwable {
-                    if(failure != null) {
-                        LOG.debug("Tx {} read operation failed: {}", identifier, failure);
-                        returnFuture.setException(new ReadFailedException(
-                                "Error reading data for path " + path, failure));
-
-                    } else {
-                        LOG.debug("Tx {} read operation succeeded", identifier, failure);
-
-                        if (readResponse instanceof ReadDataReply) {
-                            ReadDataReply reply = (ReadDataReply) readResponse;
-                            returnFuture.set(Optional.<NormalizedNode<?, ?>>fromNullable(reply.getNormalizedNode()));
-
-                        } else if (ReadDataReply.isSerializedType(readResponse)) {
-                            ReadDataReply reply = ReadDataReply.fromSerializable(readResponse);
-                            returnFuture.set(Optional.<NormalizedNode<?, ?>>fromNullable(reply.getNormalizedNode()));
-
-                        } else {
-                            returnFuture.setException(new ReadFailedException(
-                                "Invalid response reading data for path " + path));
-                        }
-                    }
-                }
-            };
-
-            Future<Object> readFuture = executeOperationAsync(new ReadData(path));
-
-            readFuture.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
-        }
-
-        @Override
-        public CheckedFuture<Boolean, ReadFailedException> dataExists(
-                final YangInstanceIdentifier path) {
-
-            LOG.debug("Tx {} dataExists called path = {}", identifier, path);
-
-            final SettableFuture<Boolean> returnFuture = SettableFuture.create();
-
-            // If there were any previous recorded put/merge/delete operation reply Futures then we
-            // must wait for them to successfully complete. This is necessary to honor the read
-            // uncommitted semantics of the public API contract. If any one fails then fail this
-            // request.
-
-            if(recordedOperationFutures.isEmpty()) {
-                finishDataExists(path, returnFuture);
-            } else {
-                LOG.debug("Tx {} dataExists: verifying {} previous recorded operations",
-                        identifier, recordedOperationFutures.size());
-
-                // Note: we make a copy of recordedOperationFutures to be on the safe side in case
-                // Futures#sequence accesses the passed List on a different thread, as
-                // recordedOperationFutures is not synchronized.
-
-                Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(
-                        Lists.newArrayList(recordedOperationFutures),
-                        actorContext.getActorSystem().dispatcher());
-                OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
-                    @Override
-                    public void onComplete(Throwable failure, Iterable<Object> notUsed)
-                            throws Throwable {
-                        if(failure != null) {
-                            LOG.debug("Tx {} dataExists: a recorded operation failed: {}",
-                                    identifier, failure);
-                            returnFuture.setException(new ReadFailedException(
-                                    "The data exists could not be performed because a previous "
-                                    + "put, merge, or delete operation failed", failure));
-                        } else {
-                            finishDataExists(path, returnFuture);
-                        }
-                    }
-                };
-
-                combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
-            }
-
-            return MappingCheckedFuture.create(returnFuture, ReadFailedException.MAPPER);
-        }
-
-        private void finishDataExists(final YangInstanceIdentifier path,
-                final SettableFuture<Boolean> returnFuture) {
-
-            LOG.debug("Tx {} finishDataExists called path = {}", identifier, path);
-
-            OnComplete<Object> onComplete = new OnComplete<Object>() {
-                @Override
-                public void onComplete(Throwable failure, Object response) throws Throwable {
-                    if(failure != null) {
-                        LOG.debug("Tx {} dataExists operation failed: {}", identifier, failure);
-                        returnFuture.setException(new ReadFailedException(
-                                "Error checking data exists for path " + path, failure));
-                    } else {
-                        LOG.debug("Tx {} dataExists operation succeeded", identifier, failure);
-
-                        if (response instanceof DataExistsReply) {
-                            returnFuture.set(Boolean.valueOf(((DataExistsReply) response).exists()));
-
-                        } else if (response.getClass().equals(DataExistsReply.SERIALIZABLE_CLASS)) {
-                            returnFuture.set(Boolean.valueOf(DataExistsReply.fromSerializable(response).exists()));
-
-                        } else {
-                            returnFuture.setException(new ReadFailedException(
-                                    "Invalid response checking exists for path " + path));
-                        }
-                    }
-                }
-            };
-
-            Future<Object> future = executeOperationAsync(new DataExists(path));
-
-            future.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
-        }
-    }
-
-    private static class NoOpTransactionContext extends AbstractTransactionContext {
-
-        private final Logger LOG = LoggerFactory.getLogger(NoOpTransactionContext.class);
-
-        private final Throwable failure;
-        private final Semaphore operationLimiter;
-
-        public NoOpTransactionContext(Throwable failure, TransactionIdentifier identifier, Semaphore operationLimiter){
-            super(identifier);
-            this.failure = failure;
-            this.operationLimiter = operationLimiter;
-        }
-
-        @Override
-        public void closeTransaction() {
-            LOG.debug("NoOpTransactionContext {} closeTransaction called", identifier);
-        }
-
-        @Override
-        public Future<ActorSelection> readyTransaction() {
-            LOG.debug("Tx {} readyTransaction called", identifier);
-            operationLimiter.release();
-            return akka.dispatch.Futures.failed(failure);
-        }
-
-        @Override
-        public void deleteData(YangInstanceIdentifier path) {
-            LOG.debug("Tx {} deleteData called path = {}", identifier, path);
-            operationLimiter.release();
-        }
-
-        @Override
-        public void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
-            LOG.debug("Tx {} mergeData called path = {}", identifier, path);
-            operationLimiter.release();
-        }
-
-        @Override
-        public void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
-            LOG.debug("Tx {} writeData called path = {}", identifier, path);
-            operationLimiter.release();
-        }
-
-        @Override
-        public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
-                YangInstanceIdentifier path) {
-            LOG.debug("Tx {} readData called path = {}", identifier, path);
-            operationLimiter.release();
-            return Futures.immediateFailedCheckedFuture(new ReadFailedException(
-                    "Error reading data for path " + path, failure));
-        }
-
-        @Override
-        public CheckedFuture<Boolean, ReadFailedException> dataExists(
-                YangInstanceIdentifier path) {
-            LOG.debug("Tx {} dataExists called path = {}", identifier, path);
-            operationLimiter.release();
-            return Futures.immediateFailedCheckedFuture(new ReadFailedException(
-                    "Error checking exists for path " + path, failure));
-        }
-    }
-
-    private static class OperationCompleter extends OnComplete<Object> {
-        private final Semaphore operationLimiter;
-        OperationCompleter(Semaphore operationLimiter){
-            this.operationLimiter = operationLimiter;
-        }
-
-        @Override
-        public void onComplete(Throwable throwable, Object o){
-            this.operationLimiter.release();
-        }
-    }
 }