- /**
- * Time interval in between transaction create retries.
- */
- private static final FiniteDuration CREATE_TX_TRY_INTERVAL =
- FiniteDuration.create(1, TimeUnit.SECONDS);
-
- /**
- * Used to enqueue the PhantomReferences for read-only TransactionProxy instances. The
- * FinalizableReferenceQueue is safe to use statically in an OSGi environment as it uses some
- * trickery to clean up its internal thread when the bundle is unloaded.
- */
- private static final FinalizableReferenceQueue phantomReferenceQueue =
- new FinalizableReferenceQueue();
-
- /**
- * This stores the TransactionProxyCleanupPhantomReference instances statically, This is
- * necessary because PhantomReferences need a hard reference so they're not garbage collected.
- * Once finalized, the TransactionProxyCleanupPhantomReference removes itself from this map
- * and thus becomes eligible for garbage collection.
- */
- private static final Map<TransactionProxyCleanupPhantomReference,
- TransactionProxyCleanupPhantomReference> phantomReferenceCache =
- new ConcurrentHashMap<>();
-
- /**
- * A PhantomReference that closes remote transactions for a TransactionProxy when it's
- * garbage collected. This is used for read-only transactions as they're not explicitly closed
- * by clients. So the only way to detect that a transaction is no longer in use and it's safe
- * to clean up is when it's garbage collected. It's inexact as to when an instance will be GC'ed
- * but TransactionProxy instances should generally be short-lived enough to avoid being moved
- * to the old generation space and thus should be cleaned up in a timely manner as the GC
- * runs on the young generation (eden, swap1...) space much more frequently.
- */
- private static class TransactionProxyCleanupPhantomReference
- extends FinalizablePhantomReference<TransactionProxy> {
-
- private final List<ActorSelection> remoteTransactionActors;
- private final AtomicBoolean remoteTransactionActorsMB;
- private final ActorContext actorContext;
- private final TransactionIdentifier identifier;
-
- protected TransactionProxyCleanupPhantomReference(TransactionProxy referent) {
- super(referent, phantomReferenceQueue);
-
- // Note we need to cache the relevant fields from the TransactionProxy as we can't
- // have a hard reference to the TransactionProxy instance itself.
-
- remoteTransactionActors = referent.remoteTransactionActors;
- remoteTransactionActorsMB = referent.remoteTransactionActorsMB;
- actorContext = referent.actorContext;
- identifier = referent.identifier;
- }
-
- @Override
- public void finalizeReferent() {
- LOG.trace("Cleaning up {} Tx actors for TransactionProxy {}",
- remoteTransactionActors.size(), identifier);
-
- phantomReferenceCache.remove(this);
-
- // Access the memory barrier volatile to ensure all previous updates to the
- // remoteTransactionActors list are visible to this thread.
-
- if(remoteTransactionActorsMB.get()) {
- for(ActorSelection actor : remoteTransactionActors) {
- LOG.trace("Sending CloseTransaction to {}", actor);
- actorContext.sendOperationAsync(actor,
- new CloseTransaction().toSerializable());
- }
- }
- }
- }
-