package org.opendaylight.controller.cluster.databroker.actors.dds;
import akka.actor.ActorRef;
+import com.google.common.base.MoreObjects;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
+import com.google.common.base.Throwables;
import com.google.common.base.Verify;
import com.google.common.util.concurrent.CheckedFuture;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.Consumer;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.NotThreadSafe;
+import org.opendaylight.controller.cluster.access.client.ConnectionEntry;
import org.opendaylight.controller.cluster.access.commands.TransactionAbortRequest;
import org.opendaylight.controller.cluster.access.commands.TransactionAbortSuccess;
import org.opendaylight.controller.cluster.access.commands.TransactionCanCommitSuccess;
import org.opendaylight.controller.cluster.access.commands.TransactionDoCommitRequest;
import org.opendaylight.controller.cluster.access.commands.TransactionPreCommitRequest;
import org.opendaylight.controller.cluster.access.commands.TransactionPreCommitSuccess;
+import org.opendaylight.controller.cluster.access.commands.TransactionPurgeRequest;
import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
+import org.opendaylight.controller.cluster.access.concepts.Request;
import org.opendaylight.controller.cluster.access.concepts.RequestFailure;
import org.opendaylight.controller.cluster.access.concepts.Response;
import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
-import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
+import org.opendaylight.mdsal.common.api.ReadFailedException;
import org.opendaylight.yangtools.concepts.Identifiable;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
/**
* Class translating transaction operations towards a particular backend shard.
* @author Robert Varga
*/
abstract class AbstractProxyTransaction implements Identifiable<TransactionIdentifier> {
- private final DistributedDataStoreClientBehavior client;
+ /**
+ * Marker object used instead of read-type of requests, which are satisfied only once. This has a lower footprint
+ * and allows compressing multiple requests into a single entry.
+ */
+ @NotThreadSafe
+ private static final class IncrementSequence {
+ private long delta = 1;
+
+ long getDelta() {
+ return delta;
+ }
+
+ void incrementDelta() {
+ delta++;
+ }
+ }
+
+ // Generic state base class. Direct instances are used for fast paths, sub-class is used for successor transitions
+ private static class State {
+ private final String string;
+
+ State(final String string) {
+ this.string = Preconditions.checkNotNull(string);
+ }
+
+ @Override
+ public final String toString() {
+ return string;
+ }
+ }
+
+ // State class used when a successor has interfered. Contains coordinator latch, the successor and previous state
+ private static final class SuccessorState extends State {
+ private final CountDownLatch latch = new CountDownLatch(1);
+ private AbstractProxyTransaction successor;
+ private State prevState;
+
+ 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);
+ 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);
+ this.successor = Preconditions.checkNotNull(successor);
+ }
+ }
+
+ 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");
+ private static final State OPEN = new State("open");
+ private static final State SEALED = new State("sealed");
+ private static final State FLUSHED = new State("flushed");
+ // Touched from client actor thread only
+ private final Deque<Object> successfulRequests = new ArrayDeque<>();
+ private final ProxyHistory parent;
+
+ // Accessed from user thread only, which may not access this object concurrently
private long sequence;
- private boolean sealed;
- AbstractProxyTransaction(final DistributedDataStoreClientBehavior client) {
- this.client = Preconditions.checkNotNull(client);
+ /*
+ * Atomic state-keeping is required to synchronize the process of propagating completed transaction state towards
+ * the backend -- which may include a successor.
+ *
+ * Successor, unlike {@link AbstractProxyTransaction#seal()} is triggered from the client actor thread, which means
+ * the successor placement needs to be atomic with regard to the application thread.
+ *
+ * In the common case, the application thread performs performs the seal operations and then "immediately" sends
+ * the corresponding message. The uncommon case is when the seal and send operations race with a connect completion
+ * or timeout, when a successor is injected.
+ *
+ * This leaves the problem of needing to completely transferring state just after all queued messages are replayed
+ * after a successor was injected, so that it can be properly sealed if we are racing. Further complication comes
+ * from lock ordering, where the successor injection works with a locked queue and locks proxy objects -- leading
+ * to a potential AB-BA deadlock in case of a naive implementation.
+ *
+ * For tracking user-visible state we use a single volatile int, which is flipped atomically from 0 to 1 exactly
+ * once in {@link AbstractProxyTransaction#seal()}. That keeps common operations fast, as they need to perform
+ * only a single volatile read to assert state correctness.
+ *
+ * For synchronizing client actor (successor-injecting) and user (commit-driving) thread, we keep a separate state
+ * variable. It uses pre-allocated objects for fast paths (i.e. no successor present) and a per-transition object
+ * for slow paths (when successor is injected/present).
+ */
+ private volatile int sealed = 0;
+ private volatile State state = OPEN;
+
+ AbstractProxyTransaction(final ProxyHistory parent) {
+ this.parent = Preconditions.checkNotNull(parent);
}
final ActorRef localActor() {
- return client.self();
+ return parent.localActor();
+ }
+
+ private void incrementSequence(final long delta) {
+ sequence += delta;
+ LOG.debug("Transaction {} incremented sequence to {}", this, sequence);
}
final long nextSequence() {
- return sequence++;
+ final long ret = sequence++;
+ LOG.debug("Transaction {} allocated sequence {}", this, ret);
+ return ret;
}
final void delete(final YangInstanceIdentifier path) {
- checkSealed();
+ checkReadWrite();
+ checkNotSealed();
doDelete(path);
}
final void merge(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
- checkSealed();
+ checkReadWrite();
+ checkNotSealed();
doMerge(path, data);
}
final void write(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
- checkSealed();
+ checkReadWrite();
+ checkNotSealed();
doWrite(path, data);
}
final CheckedFuture<Boolean, ReadFailedException> exists(final YangInstanceIdentifier path) {
- checkSealed();
+ checkNotSealed();
return doExists(path);
}
final CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read(final YangInstanceIdentifier path) {
- checkSealed();
+ checkNotSealed();
return doRead(path);
}
- final void sendRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> completer) {
- client.sendRequest(request, completer);
+ final void sendRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback) {
+ LOG.debug("Transaction proxy {} sending request {} callback {}", this, request, callback);
+ parent.sendRequest(request, callback);
}
/**
- * Seals this transaction when ready.
+ * Seal this transaction before it is either committed or aborted.
*/
final void seal() {
- checkSealed();
+ // Transition user-visible state first
+ final boolean success = SEALED_UPDATER.compareAndSet(this, 0, 1);
+ Preconditions.checkState(success, "Proxy %s was already sealed", getIdentifier());
+ internalSeal();
+ }
+
+ final void ensureSealed() {
+ if (SEALED_UPDATER.compareAndSet(this, 0, 1)) {
+ internalSeal();
+ }
+ }
+
+ private void internalSeal() {
doSeal();
- sealed = true;
+ parent.onTransactionSealed(this);
+
+ // Now deal with state transfer, which can occur via successor or a follow-up canCommit() or directCommit().
+ if (!STATE_UPDATER.compareAndSet(this, OPEN, SEALED)) {
+ // Slow path: wait for the successor to complete
+ final AbstractProxyTransaction successor = awaitSuccessor();
+
+ // At this point the successor has completed transition and is possibly visible by the user thread, which is
+ // still stuck here. The successor has not seen final part of our state, nor the fact it is sealed.
+ // Propagate state and seal the successor.
+ flushState(successor);
+ successor.ensureSealed();
+ }
+ }
+
+ private void checkNotSealed() {
+ Preconditions.checkState(sealed == 0, "Transaction %s has already been sealed", getIdentifier());
}
private void checkSealed() {
- Preconditions.checkState(sealed, "Transaction %s has not been sealed yet", getIdentifier());
+ Preconditions.checkState(sealed != 0, "Transaction %s has not been sealed yet", getIdentifier());
+ }
+
+ private SuccessorState getSuccessorState() {
+ final State local = state;
+ Verify.verify(local instanceof SuccessorState, "State %s has unexpected class", local);
+ return (SuccessorState) local;
+ }
+
+ private void checkReadWrite() {
+ if (isSnapshotOnly()) {
+ throw new UnsupportedOperationException("Transaction " + getIdentifier() + " is a read-only snapshot");
+ }
+ }
+
+ final void recordSuccessfulRequest(final @Nonnull TransactionRequest<?> req) {
+ successfulRequests.add(Verify.verifyNotNull(req));
+ }
+
+ final void recordFinishedRequest() {
+ final Object last = successfulRequests.peekLast();
+ if (last instanceof IncrementSequence) {
+ ((IncrementSequence) last).incrementDelta();
+ } else {
+ successfulRequests.addLast(new IncrementSequence());
+ }
}
/**
* being sent to the backend.
*/
final void abort() {
- checkSealed();
+ checkNotSealed();
doAbort();
+ parent.abortTransaction(this);
}
- void abort(final VotingFuture<Void> ret) {
+ final void abort(final VotingFuture<Void> ret) {
checkSealed();
- sendRequest(new TransactionAbortRequest(getIdentifier(), nextSequence(), localActor()), t -> {
+ sendAbort(t -> {
if (t instanceof TransactionAbortSuccess) {
ret.voteYes();
} else if (t instanceof RequestFailure) {
} else {
ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
}
+
+ // This is a terminal request, hence we do not need to record it
+ LOG.debug("Transaction {} abort completed", this);
+ purge();
});
}
+ final void sendAbort(final Consumer<Response<?, ?>> callback) {
+ sendRequest(new TransactionAbortRequest(getIdentifier(), nextSequence(), localActor()), callback);
+ }
+
/**
* Commit this transaction, possibly in a coordinated fashion.
*
* @return Future completion
*/
final ListenableFuture<Boolean> directCommit() {
+ checkReadWrite();
checkSealed();
- final SettableFuture<Boolean> ret = SettableFuture.create();
- sendRequest(Verify.verifyNotNull(doCommit(false)), t -> {
- if (t instanceof TransactionCommitSuccess) {
- ret.set(Boolean.TRUE);
- } else if (t instanceof RequestFailure) {
- ret.setException(((RequestFailure<?, ?>) t).getCause());
- } else {
- ret.setException(new IllegalStateException("Unhandled response " + t.getClass()));
+ // Precludes startReconnect() from interfering with the fast path
+ synchronized (this) {
+ if (STATE_UPDATER.compareAndSet(this, SEALED, FLUSHED)) {
+ final SettableFuture<Boolean> ret = SettableFuture.create();
+ sendRequest(Verify.verifyNotNull(commitRequest(false)), t -> {
+ if (t instanceof TransactionCommitSuccess) {
+ ret.set(Boolean.TRUE);
+ } else if (t instanceof RequestFailure) {
+ ret.setException(((RequestFailure<?, ?>) t).getCause());
+ } else {
+ ret.setException(new IllegalStateException("Unhandled response " + t.getClass()));
+ }
+
+ // This is a terminal request, hence we do not need to record it
+ LOG.debug("Transaction {} directCommit completed", this);
+ purge();
+ });
+
+ return ret;
}
- });
- return ret;
+ }
+
+ // We have had some interference with successor injection, wait for it to complete and defer to the successor.
+ return awaitSuccessor().directCommit();
}
- void canCommit(final VotingFuture<?> ret) {
+ final void canCommit(final VotingFuture<?> ret) {
+ checkReadWrite();
checkSealed();
- sendRequest(Verify.verifyNotNull(doCommit(true)), t -> {
- if (t instanceof TransactionCanCommitSuccess) {
- ret.voteYes();
- } else if (t instanceof RequestFailure) {
- ret.voteNo(((RequestFailure<?, ?>) t).getCause());
- } else {
- ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
+ // Precludes startReconnect() from interfering with the fast path
+ synchronized (this) {
+ if (STATE_UPDATER.compareAndSet(this, SEALED, FLUSHED)) {
+ final TransactionRequest<?> req = Verify.verifyNotNull(commitRequest(true));
+
+ sendRequest(req, t -> {
+ if (t instanceof TransactionCanCommitSuccess) {
+ ret.voteYes();
+ } else if (t instanceof RequestFailure) {
+ ret.voteNo(((RequestFailure<?, ?>) t).getCause());
+ } else {
+ ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
+ }
+
+ recordSuccessfulRequest(req);
+ LOG.debug("Transaction {} canCommit completed", this);
+ });
+
+ return;
}
- });
+ }
+
+ // We have had some interference with successor injection, wait for it to complete and defer to the successor.
+ awaitSuccessor().canCommit(ret);
}
- void preCommit(final VotingFuture<?> ret) {
+ private AbstractProxyTransaction awaitSuccessor() {
+ return getSuccessorState().await();
+ }
+
+ final void preCommit(final VotingFuture<?> ret) {
+ checkReadWrite();
checkSealed();
- sendRequest(new TransactionPreCommitRequest(getIdentifier(), nextSequence(), localActor()), t -> {
+ final TransactionRequest<?> req = new TransactionPreCommitRequest(getIdentifier(), nextSequence(),
+ localActor());
+ sendRequest(req, t -> {
if (t instanceof TransactionPreCommitSuccess) {
ret.voteYes();
} else if (t instanceof RequestFailure) {
} else {
ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
}
+
+ onPreCommitComplete(req);
});
}
- void doCommit(final VotingFuture<?> ret) {
+ private void onPreCommitComplete(final TransactionRequest<?> req) {
+ /*
+ * The backend has agreed that the transaction has entered PRE_COMMIT phase, meaning it will be committed
+ * to storage after the timeout completes.
+ *
+ * All state has been replicated to the backend, hence we do not need to keep it around. Retain only
+ * the precommit request, so we know which request to use for resync.
+ */
+ LOG.debug("Transaction {} preCommit completed, clearing successfulRequests", this);
+ successfulRequests.clear();
+
+ // TODO: this works, but can contain some useless state (like batched operations). Create an empty
+ // equivalent of this request and store that.
+ recordSuccessfulRequest(req);
+ }
+
+ final void doCommit(final VotingFuture<?> ret) {
+ checkReadWrite();
checkSealed();
sendRequest(new TransactionDoCommitRequest(getIdentifier(), nextSequence(), localActor()), t -> {
} else {
ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
}
+
+ LOG.debug("Transaction {} doCommit completed", this);
+ purge();
+ });
+ }
+
+ void purge() {
+ successfulRequests.clear();
+
+ final TransactionRequest<?> req = new TransactionPurgeRequest(getIdentifier(), nextSequence(), localActor());
+ sendRequest(req, t -> {
+ LOG.debug("Transaction {} purge completed", this);
+ parent.completeTransaction(this);
});
}
- abstract TransactionRequest<?> doCommit(boolean coordinated);
+ // Called with the connection unlocked
+ final synchronized void startReconnect() {
+ // At this point canCommit/directCommit are blocked, we assert a new successor state, retrieving the previous
+ // state. This method is called with the queue still unlocked.
+ final SuccessorState nextState = new SuccessorState();
+ final State prevState = STATE_UPDATER.getAndSet(this, nextState);
+
+ LOG.debug("Start reconnect of proxy {} previous state {}", this, prevState);
+ Verify.verify(!(prevState instanceof SuccessorState), "Proxy %s duplicate reconnect attempt after %s", this,
+ prevState);
+
+ // We have asserted a slow-path state, seal(), canCommit(), directCommit() are forced to slow paths, which will
+ // wait until we unblock nextState's latch before accessing state. Now we record prevState for later use and we
+ // are done.
+ nextState.setPrevState(prevState);
+ }
+
+ // Called with the connection locked
+ final void replayMessages(final AbstractProxyTransaction successor,
+ final Iterable<ConnectionEntry> enqueuedEntries) {
+ final SuccessorState local = getSuccessorState();
+ local.setSuccessor(successor);
+
+ // Replay successful requests first
+ for (Object obj : successfulRequests) {
+ if (obj instanceof TransactionRequest) {
+ LOG.debug("Forwarding successful request {} to successor {}", obj, successor);
+ successor.handleForwardedRemoteRequest((TransactionRequest<?>) obj, response -> { });
+ } else {
+ Verify.verify(obj instanceof IncrementSequence);
+ successor.incrementSequence(((IncrementSequence) obj).getDelta());
+ }
+ }
+ LOG.debug("{} replayed {} successful requests", getIdentifier(), successfulRequests.size());
+ successfulRequests.clear();
+
+ // Now replay whatever is in the connection
+ final Iterator<ConnectionEntry> it = enqueuedEntries.iterator();
+ while (it.hasNext()) {
+ final ConnectionEntry e = it.next();
+ final Request<?, ?> req = e.getRequest();
+
+ if (getIdentifier().equals(req.getTarget())) {
+ Verify.verify(req instanceof TransactionRequest, "Unhandled request %s", req);
+ LOG.debug("Forwarding queued request{} to successor {}", req, successor);
+ successor.handleForwardedRemoteRequest((TransactionRequest<?>) req, e.getCallback());
+ it.remove();
+ }
+ }
+
+ /*
+ * Check the state at which we have started the reconnect attempt. State transitions triggered while we were
+ * reconnecting have been forced to slow paths, which will be unlocked once we unblock the state latch
+ * at the end of this method.
+ */
+ final State prevState = local.getPrevState();
+ if (SEALED.equals(prevState)) {
+ LOG.debug("Proxy {} reconnected while being sealed, propagating state to successor {}", this, successor);
+ flushState(successor);
+ successor.ensureSealed();
+ }
+ }
+
+ // Called with the connection locked
+ final void finishReconnect() {
+ final SuccessorState local = getSuccessorState();
+ LOG.debug("Finishing reconnect of proxy {}", this);
- abstract void doDelete(final YangInstanceIdentifier path);
+ // All done, release the latch, unblocking seal() and canCommit() slow paths
+ local.finish();
+ }
- abstract void doMerge(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data);
+ /**
+ * Invoked from a retired connection for requests which have been in-flight and need to be re-adjusted
+ * and forwarded to the successor connection.
+ *
+ * @param request Request to be forwarded
+ * @param callback Original callback
+ */
+ final void replayRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback) {
+ final AbstractProxyTransaction successor = getSuccessorState().getSuccessor();
+
+ if (successor instanceof LocalProxyTransaction) {
+ forwardToLocal((LocalProxyTransaction)successor, request, callback);
+ } else if (successor instanceof RemoteProxyTransaction) {
+ forwardToRemote((RemoteProxyTransaction)successor, request, callback);
+ } else {
+ throw new IllegalStateException("Unhandled successor " + successor);
+ }
+ }
- abstract void doWrite(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data);
+ abstract boolean isSnapshotOnly();
- abstract CheckedFuture<Boolean, ReadFailedException> doExists(final YangInstanceIdentifier path);
+ abstract void doDelete(YangInstanceIdentifier path);
- abstract CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> doRead(
- final YangInstanceIdentifier path);
+ abstract void doMerge(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
+
+ abstract void doWrite(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
+
+ abstract CheckedFuture<Boolean, ReadFailedException> doExists(YangInstanceIdentifier path);
+
+ abstract CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> doRead(YangInstanceIdentifier path);
abstract void doSeal();
abstract void doAbort();
+
+ @GuardedBy("this")
+ abstract void flushState(AbstractProxyTransaction successor);
+
+ abstract TransactionRequest<?> commitRequest(boolean coordinated);
+
+ /**
+ * Invoked from {@link RemoteProxyTransaction} when it replays its successful requests to its successor. There is
+ * no equivalent of this call from {@link LocalProxyTransaction} because it does not send a request until all
+ * operations are packaged in the message.
+ *
+ * <p>
+ * Note: this method is invoked by the predecessor on the successor.
+ *
+ * @param request Request which needs to be forwarded
+ * @param callback Callback to be invoked once the request completes
+ */
+ abstract void handleForwardedRemoteRequest(TransactionRequest<?> request,
+ @Nullable Consumer<Response<?, ?>> callback);
+
+ /**
+ * Replay a request originating in this proxy to a successor remote proxy.
+ */
+ abstract void forwardToRemote(RemoteProxyTransaction successor, TransactionRequest<?> request,
+ Consumer<Response<?, ?>> callback);
+
+ /**
+ * Replay a request originating in this proxy to a successor local proxy.
+ */
+ abstract void forwardToLocal(LocalProxyTransaction successor, TransactionRequest<?> request,
+ Consumer<Response<?, ?>> callback);
+
+ @Override
+ public final String toString() {
+ return MoreObjects.toStringHelper(this).add("identifier", getIdentifier()).add("state", state).toString();
+ }
}
Code Review / controller.git / blobdiff