+ state = CLOSED_STATE;
+
+ // Send a close transaction chain request to each and every shard
+ actorContext.broadcast(new CloseTransactionChain(transactionChainId));
+ }
+
+ private ChainedTransactionProxy allocateWriteTransaction(TransactionProxy.TransactionType type) {
+ checkReadyState();
+
+ ChainedTransactionProxy txProxy = new ChainedTransactionProxy(actorContext, type);
+ STATE_UPDATER.compareAndSet(this, IDLE_STATE, new Allocated());
+
+ return txProxy;
+ }
+
+ private void checkReadyState() {
+ Preconditions.checkState(state.isReady(), "Previous transaction %s is not ready yet",
+ state.getReadyFutures().getKey());
+ }
+
+ private class ChainedTransactionProxy extends TransactionProxy {
+
+ ChainedTransactionProxy(ActorContext actorContext, TransactionType transactionType) {
+ super(actorContext, transactionType, transactionChainId);
+ }
+
+ @Override
+ protected void onTransactionReady(List<Future<ActorSelection>> readyFutures) {
+ LOG.debug("onTransactionReady {} pending readyFutures size {} chain {}", getIdentifier(), readyFutures.size(), TransactionChainProxy.this.transactionChainId);
+ state.setReadyFutures(getIdentifier(), readyFutures);
+ }
+
+ /**
+ * This method is overridden to ensure the previous Tx's ready operations complete
+ * before we create the next shard Tx in the chain to avoid creation failures if the
+ * previous Tx's ready operations haven't completed yet.
+ */
+ @Override
+ protected Future<Object> sendCreateTransaction(final ActorSelection shard,
+ final Object serializedCreateMessage) {
+
+ // Check if there are any previous ready Futures, otherwise let the super class handle it.
+ // The second check is done to ensure the the previous ready Futures aren't for this
+ // Tx instance as deadlock would occur if we tried to wait on our own Futures. This can
+ // occur in this scenario:
+ //
+ // - the TransactionProxy is created and the client does a write.
+ //
+ // - the TransactionProxy then attempts to create the shard Tx. However it first
+ // sends a FindPrimaryShard message to the shard manager to find the local shard
+ // This call is done async.
+ //
+ // - the client submits the Tx and the TransactionProxy is readied and we cache
+ // the ready Futures here.
+ //
+ // - then the FindPrimaryShard call completes and this method is called to create
+ // the shard Tx. However the cached Futures were from the ready on this Tx. If we
+ // tried to wait on them, it would cause a form of deadlock as the ready Future
+ // would be waiting on the Tx create Future and vice versa.
+ SimpleEntry<Object, List<Future<ActorSelection>>> readyFuturesEntry = state.getReadyFutures();
+ List<Future<ActorSelection>> readyFutures = readyFuturesEntry.getValue();
+ if(readyFutures.isEmpty() || getIdentifier().equals(readyFuturesEntry.getKey())) {
+ return super.sendCreateTransaction(shard, serializedCreateMessage);
+ }
+
+ // Combine the ready Futures into 1.
+ Future<Iterable<ActorSelection>> combinedFutures = akka.dispatch.Futures.sequence(
+ readyFutures, actorContext.getActorSystem().dispatcher());
+
+ // Add a callback for completion of the combined Futures.
+ final Promise<Object> createTxPromise = akka.dispatch.Futures.promise();
+ OnComplete<Iterable<ActorSelection>> onComplete = new OnComplete<Iterable<ActorSelection>>() {
+ @Override
+ public void onComplete(Throwable failure, Iterable<ActorSelection> notUsed) {
+ if(failure != null) {
+ // A Ready Future failed so fail the returned Promise.
+ createTxPromise.failure(failure);
+ } else {
+ // Send the CreateTx message and use the resulting Future to complete the
+ // returned Promise.
+ createTxPromise.completeWith(actorContext.executeOperationAsync(shard,
+ serializedCreateMessage));
+ }
+ }
+ };
+
+ combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
+
+ return createTxPromise.future();
+ }