+ * <p>
+ * When a user operation encounters this state, it synchronizes on the it and wait until reconnection completes,
+ * at which point the request is routed to the successor transaction. This is a relatively heavy-weight solution
+ * to the problem of state transfer, but the user will observe it only if the race condition is hit.
+ */
+ private static class SuccessorState extends State {
+ private final CountDownLatch latch = new CountDownLatch(1);
+ private AbstractProxyTransaction successor;
+ private State prevState;
+
+ // SUCCESSOR + DONE
+ private boolean done;
+
+ SuccessorState() {
+ super("SUCCESSOR");
+ }
+
+ // Synchronize with succession process and return the successor
+ AbstractProxyTransaction await() {
+ try {
+ latch.await();
+ } catch (InterruptedException e) {
+ LOG.warn("Interrupted while waiting for latch of {}", successor);
+ throw Throwables.propagate(e);
+ }
+ return successor;
+ }
+
+ void finish() {
+ latch.countDown();
+ }
+
+ State getPrevState() {
+ return prevState;
+ }
+
+ void setPrevState(final State prevState) {
+ Verify.verify(this.prevState == null, "Attempted to set previous state to %s when we already have %s",
+ prevState, this.prevState);
+ this.prevState = Preconditions.checkNotNull(prevState);
+ }
+
+ // To be called from safe contexts, where successor is known to be completed
+ AbstractProxyTransaction getSuccessor() {
+ return Verify.verifyNotNull(successor);
+ }
+
+ void setSuccessor(final AbstractProxyTransaction successor) {
+ Verify.verify(this.successor == null, "Attempted to set successor to %s when we already have %s",
+ successor, this.successor);
+ this.successor = Preconditions.checkNotNull(successor);
+ }
+
+ boolean isDone() {
+ return done;
+ }
+
+ void setDone() {
+ done = true;
+ }
+ }
+
+ private static final Logger LOG = LoggerFactory.getLogger(AbstractProxyTransaction.class);
+ private static final AtomicIntegerFieldUpdater<AbstractProxyTransaction> SEALED_UPDATER =
+ AtomicIntegerFieldUpdater.newUpdater(AbstractProxyTransaction.class, "sealed");
+ private static final AtomicReferenceFieldUpdater<AbstractProxyTransaction, State> STATE_UPDATER =
+ AtomicReferenceFieldUpdater.newUpdater(AbstractProxyTransaction.class, State.class, "state");
+
+ /**
+ * Transaction has been open and is being actively worked on.
+ */
+ private static final State OPEN = new State("OPEN");
+
+ /**
+ * Transaction has been sealed by the user, but it has not completed flushing to the backed, yet. This is
+ * a transition state, as we are waiting for the user to initiate commit procedures.
+ *
+ * <p>
+ * Since the reconnect mechanics relies on state replay for transactions, this state needs to be flushed into the
+ * queue to re-create state in successor transaction (which may be based on different messages as locality may have
+ * changed). Hence the transition to {@link #FLUSHED} state needs to be handled in a thread-safe manner.
+ */
+ private static final State SEALED = new State("SEALED");
+
+ /**
+ * Transaction state has been flushed into the queue, i.e. it is visible by the successor and potentially
+ * the backend. At this point the transaction does not hold any state besides successful requests, all other state
+ * is held either in the connection's queue or the successor object.
+ *
+ * <p>
+ * Transition to this state indicates we have all input from the user we need to initiate the correct commit
+ * protocol.
+ */
+ private static final State FLUSHED = new State("FLUSHED");
+
+ /**
+ * Transaction state has been completely resolved, we have received confirmation of the transaction fate from
+ * the backend. The only remaining task left to do is finishing up the state cleanup, which is done via purge
+ * request. We need to hang on to the transaction until that is done, as we have to make sure backend completes
+ * purging its state -- otherwise we could have a leak on the backend.