*/
package org.opendaylight.controller.cluster.access.client;
+import static java.util.Objects.requireNonNull;
+
import akka.actor.ActorRef;
import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Preconditions;
-import com.google.common.base.Verify;
+import com.google.common.base.MoreObjects;
+import com.google.common.base.MoreObjects.ToStringHelper;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
-import java.util.ArrayDeque;
+import java.util.Collection;
+import java.util.List;
import java.util.Optional;
-import java.util.Queue;
+import java.util.OptionalLong;
import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Consumer;
-import javax.annotation.Nonnull;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.NotThreadSafe;
+import org.checkerframework.checker.lock.qual.GuardedBy;
+import org.checkerframework.checker.lock.qual.Holding;
+import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.controller.cluster.access.concepts.Request;
import org.opendaylight.controller.cluster.access.concepts.RequestException;
import org.opendaylight.controller.cluster.access.concepts.Response;
import org.opendaylight.controller.cluster.access.concepts.ResponseEnvelope;
+import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import scala.concurrent.duration.FiniteDuration;
/**
* Base class for a connection to the backend. Responsible to queueing and dispatch of requests toward the backend.
* Can be in three conceptual states: Connecting, Connected and Reconnecting, which are represented by public final
- * classes exposed from this package.
- *
- * @author Robert Varga
+ * classes exposed from this package. This class NOT thread-safe, not are its subclasses expected to be thread-safe.
*/
-@NotThreadSafe
-public abstract class AbstractClientConnection<T extends BackendInfo> {
+public abstract sealed class AbstractClientConnection<T extends BackendInfo>
+ permits AbstractReceivingClientConnection, ConnectingClientConnection {
private static final Logger LOG = LoggerFactory.getLogger(AbstractClientConnection.class);
- // Keep these constants in nanoseconds, as that prevents unnecessary conversions in the fast path
- @VisibleForTesting
- static final long NO_PROGRESS_TIMEOUT_NANOS = TimeUnit.MINUTES.toNanos(15);
- @VisibleForTesting
- static final long REQUEST_TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(30);
+ /*
+ * Timers involved in communication with the backend. There are three tiers which are spaced out to allow for
+ * recovery at each tier. Keep these constants in nanoseconds, as that prevents unnecessary conversions in the fast
+ * path.
+ */
+ /**
+ * Backend aliveness timer. This is reset whenever we receive a response from the backend and kept armed whenever
+ * we have an outstanding request. If when this time expires, we tear down this connection and attempt to reconnect
+ * it.
+ */
+ public static final long DEFAULT_BACKEND_ALIVE_TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(30);
+
+ /**
+ * Request timeout. If the request fails to complete within this time since it was originally enqueued, we time
+ * the request out.
+ */
+ public static final long DEFAULT_REQUEST_TIMEOUT_NANOS = TimeUnit.MINUTES.toNanos(2);
+
+ /**
+ * No progress timeout. A client fails to make any forward progress in this time, it will terminate itself.
+ */
+ public static final long DEFAULT_NO_PROGRESS_TIMEOUT_NANOS = TimeUnit.MINUTES.toNanos(15);
+
+ // Emit a debug entry if we sleep for more that this amount
+ private static final long DEBUG_DELAY_NANOS = TimeUnit.MILLISECONDS.toNanos(100);
+
+ // Upper bound on the time a thread is forced to sleep to keep queue size under control
+ private static final long MAX_DELAY_SECONDS = 5;
+ private static final long MAX_DELAY_NANOS = TimeUnit.SECONDS.toNanos(MAX_DELAY_SECONDS);
+
+ private final Lock lock = new ReentrantLock();
+ private final @NonNull ClientActorContext context;
+ private final @NonNull Long cookie;
+ private final String backendName;
+ @GuardedBy("lock")
+ private final TransmitQueue queue;
+
+ @GuardedBy("lock")
+ private boolean haveTimer;
- private final Queue<ConnectionEntry> pending;
- private final ClientActorContext context;
- private final Long cookie;
+ /**
+ * Time reference when we saw any activity from the backend.
+ */
+ private long lastReceivedTicks;
- private volatile ReconnectForwarder successor;
private volatile RequestException poisoned;
- private long lastProgress;
- private AbstractClientConnection(final ClientActorContext context, final Long cookie,
- final Queue<ConnectionEntry> pending) {
- this.context = Preconditions.checkNotNull(context);
- this.cookie = Preconditions.checkNotNull(cookie);
- this.pending = Preconditions.checkNotNull(pending);
- this.lastProgress = readTime();
+ // Private constructor to avoid code duplication.
+ private AbstractClientConnection(final AbstractClientConnection<T> oldConn, final TransmitQueue newQueue,
+ final String backendName) {
+ context = oldConn.context;
+ cookie = oldConn.cookie;
+ this.backendName = requireNonNull(backendName);
+ queue = requireNonNull(newQueue);
+ // Will be updated in finishReplay if needed.
+ lastReceivedTicks = oldConn.lastReceivedTicks;
+ }
+
+ // This constructor is only to be called by ConnectingClientConnection constructor.
+ // Do not allow subclassing outside of this package
+ AbstractClientConnection(final ClientActorContext context, final Long cookie, final String backendName,
+ final int queueDepth) {
+ this.context = requireNonNull(context);
+ this.cookie = requireNonNull(cookie);
+ this.backendName = requireNonNull(backendName);
+ queue = new TransmitQueue.Halted(queueDepth);
+ lastReceivedTicks = currentTime();
}
+ // This constructor is only to be called (indirectly) by ReconnectingClientConnection constructor.
// Do not allow subclassing outside of this package
- AbstractClientConnection(final ClientActorContext context, final Long cookie) {
- this(context, cookie, new ArrayDeque<>(1));
+ AbstractClientConnection(final AbstractClientConnection<T> oldConn) {
+ this(oldConn, new TransmitQueue.Halted(oldConn.queue, oldConn.currentTime()), oldConn.backendName);
}
+ // This constructor is only to be called (indirectly) by ConnectedClientConnection constructor.
// Do not allow subclassing outside of this package
- AbstractClientConnection(final AbstractClientConnection<T> oldConnection) {
- this(oldConnection.context, oldConnection.cookie, oldConnection.pending);
+ AbstractClientConnection(final AbstractClientConnection<T> oldConn, final T newBackend,
+ final int queueDepth) {
+ this(oldConn, new TransmitQueue.Transmitting(oldConn.queue, queueDepth, newBackend, oldConn.currentTime(),
+ requireNonNull(oldConn.context).messageSlicer()), newBackend.getName());
}
- public final ClientActorContext context() {
+ public final @NonNull ClientActorContext context() {
return context;
}
- public final @Nonnull Long cookie() {
+ public final @NonNull Long cookie() {
return cookie;
}
- public final ActorRef localActor() {
+ public final @NonNull ActorRef localActor() {
return context.self();
}
- final long readTime() {
+ public final long currentTime() {
return context.ticker().read();
}
- final Queue<ConnectionEntry> pending() {
- return pending;
+ /**
+ * Send a request to the backend and invoke a specified callback when it finishes. This method is safe to invoke
+ * from any thread.
+ *
+ * <p>This method may put the caller thread to sleep in order to throttle the request rate.
+ * The callback may be called before the sleep finishes.
+ *
+ * @param request Request to send
+ * @param callback Callback to invoke
+ */
+ public final void sendRequest(final Request<?, ?> request, final Consumer<Response<?, ?>> callback) {
+ final long now = currentTime();
+ sendEntry(new ConnectionEntry(request, callback, now), now);
}
/**
* Send a request to the backend and invoke a specified callback when it finishes. This method is safe to invoke
* from any thread.
*
+ * <p>
+ * Note that unlike {@link #sendRequest(Request, Consumer)}, this method does not exert backpressure, hence it
+ * should never be called from an application thread and serves mostly for moving requests between queues.
+ *
* @param request Request to send
* @param callback Callback to invoke
+ * @param enqueuedTicks Time (according to {@link #currentTime()} of request enqueue
*/
- public final void sendRequest(final Request<?, ?> request, final Consumer<Response<?, ?>> callback) {
- Preconditions.checkState(poisoned == null, "Connection %s has been poisoned", this);
+ public final void enqueueRequest(final Request<?, ?> request, final Consumer<Response<?, ?>> callback,
+ final long enqueuedTicks) {
+ enqueueEntry(new ConnectionEntry(request, callback, enqueuedTicks), currentTime());
+ }
- final ReconnectForwarder beforeQueue = successor;
- final ConnectionEntry entry = new ConnectionEntry(request, callback, readTime());
- if (beforeQueue != null) {
- LOG.trace("Forwarding entry {} from {} to {}", entry, this, beforeQueue);
- beforeQueue.forwardEntry(entry);
- return;
+ private long enqueueOrForward(final ConnectionEntry entry, final long now) {
+ lock.lock();
+ try {
+ commonEnqueue(entry, now);
+ return queue.enqueueOrForward(entry, now);
+ } finally {
+ lock.unlock();
}
+ }
- enqueueEntry(entry);
+ /**
+ * Enqueue an entry, possibly also transmitting it.
+ */
+ public final void enqueueEntry(final ConnectionEntry entry, final long now) {
+ lock.lock();
+ try {
+ commonEnqueue(entry, now);
+ queue.enqueueOrReplay(entry, now);
+ } finally {
+ lock.unlock();
+ }
+ }
- final ReconnectForwarder afterQueue = successor;
- if (afterQueue != null) {
- synchronized (this) {
- spliceToSuccessor(afterQueue);
- }
+ @Holding("lock")
+ private void commonEnqueue(final ConnectionEntry entry, final long now) {
+ final RequestException maybePoison = poisoned;
+ if (maybePoison != null) {
+ throw new IllegalStateException("Connection " + this + " has been poisoned", maybePoison);
+ }
+
+ if (queue.isEmpty()) {
+ // The queue is becoming non-empty, schedule a timer.
+ scheduleTimer(entry.getEnqueuedTicks() + context.config().getRequestTimeout() - now);
}
}
- public final synchronized void setForwarder(final ReconnectForwarder forwarder) {
- Verify.verify(successor == null, "Successor {} already set on connection {}", successor, this);
- successor = Preconditions.checkNotNull(forwarder);
- LOG.debug("Connection {} superseded by {}, splicing queue", this, successor);
- spliceToSuccessor(forwarder);
+ // To be called from ClientActorBehavior on ConnectedClientConnection after entries are replayed.
+ final void cancelDebt() {
+ queue.cancelDebt(currentTime());
}
public abstract Optional<T> getBackendInfo();
- @GuardedBy("this")
- void spliceToSuccessor(final ReconnectForwarder successor) {
- ConnectionEntry entry = pending.poll();
- while (entry != null) {
- successor.forwardEntry(entry);
- entry = pending.poll();
- }
+ final Collection<ConnectionEntry> startReplay() {
+ lock.lock();
+ return queue.drain();
+ }
+
+ @Holding("lock")
+ final void finishReplay(final ReconnectForwarder forwarder) {
+ setForwarder(forwarder);
+
+ /*
+ * The process of replaying all messages may have taken a significant chunk of time, depending on type
+ * of messages, queue depth and available processing power. In extreme situations this may have already
+ * exceeded BACKEND_ALIVE_TIMEOUT_NANOS, in which case we are running the risk of not making reasonable forward
+ * progress before we start a reconnect cycle.
+ *
+ * Note that the timer is armed after we have sent the first message, hence we should be seeing a response
+ * from the backend before we see a timeout, simply due to how the mailbox operates.
+ *
+ * At any rate, reset the timestamp once we complete reconnection (which an atomic transition from the
+ * perspective of outside world), as that makes it a bit easier to reason about timing of events.
+ */
+ lastReceivedTicks = currentTime();
+ lock.unlock();
+ }
+
+ @Holding("lock")
+ final void setForwarder(final ReconnectForwarder forwarder) {
+ queue.setForwarder(forwarder, currentTime());
}
- final ConnectionEntry dequeEntry() {
- lastProgress = readTime();
- return pending.poll();
+ @Holding("lock")
+ abstract ClientActorBehavior<T> lockedReconnect(ClientActorBehavior<T> current,
+ RequestException runtimeRequestException);
+
+ final void sendEntry(final ConnectionEntry entry, final long now) {
+ long delay = enqueueOrForward(entry, now);
+ try {
+ if (delay >= DEBUG_DELAY_NANOS) {
+ if (delay > MAX_DELAY_NANOS) {
+ LOG.info("Capping {} throttle delay from {} to {} seconds", this,
+ TimeUnit.NANOSECONDS.toSeconds(delay), MAX_DELAY_SECONDS, new Throwable());
+ delay = MAX_DELAY_NANOS;
+ }
+ if (LOG.isDebugEnabled()) {
+ LOG.debug("{}: Sleeping for {}ms on connection {}", context.persistenceId(),
+ TimeUnit.NANOSECONDS.toMillis(delay), this);
+ }
+ }
+ TimeUnit.NANOSECONDS.sleep(delay);
+ } catch (InterruptedException e) {
+ Thread.currentThread().interrupt();
+ LOG.debug("Interrupted after sleeping {}ns", currentTime() - now, e);
+ }
}
- void enqueueEntry(final ConnectionEntry entry) {
- pending.add(entry);
+ final ClientActorBehavior<T> reconnect(final ClientActorBehavior<T> current, final RequestException cause) {
+ lock.lock();
+ try {
+ return lockedReconnect(current, cause);
+ } finally {
+ lock.unlock();
+ }
}
/**
*
* @param delay Delay, in nanoseconds
*/
- private void scheduleTimer(final FiniteDuration delay) {
- LOG.debug("{}: scheduling timeout in {}", context.persistenceId(), delay);
- context.executeInActor(this::runTimer, delay);
+ @Holding("lock")
+ private void scheduleTimer(final long delay) {
+ if (haveTimer) {
+ LOG.debug("{}: timer already scheduled on {}", context.persistenceId(), this);
+ return;
+ }
+ if (queue.hasSuccessor()) {
+ LOG.debug("{}: connection {} has a successor, not scheduling timer", context.persistenceId(), this);
+ return;
+ }
+
+ // If the delay is negative, we need to schedule an action immediately. While the caller could have checked
+ // for that condition and take appropriate action, but this is more convenient and less error-prone.
+ final long normalized = delay <= 0 ? 0 : Math.min(delay, context.config().getBackendAlivenessTimerInterval());
+
+ final FiniteDuration dur = FiniteDuration.fromNanos(normalized);
+ LOG.debug("{}: connection {} scheduling timeout in {}", context.persistenceId(), this, dur);
+ context.executeInActor(this::runTimer, dur);
+ haveTimer = true;
}
/**
* Check this queue for timeout and initiate reconnection if that happened. If the queue has not made progress
- * in {@link #NO_PROGRESS_TIMEOUT_NANOS} nanoseconds, it will be aborted.
+ * in {@link #DEFAULT_NO_PROGRESS_TIMEOUT_NANOS} nanoseconds, it will be aborted.
*
* @param current Current behavior
* @return Next behavior to use
*/
@VisibleForTesting
final ClientActorBehavior<T> runTimer(final ClientActorBehavior<T> current) {
- final long now = readTime();
-
- if (!isEmpty()) {
- final long ticksSinceProgress = now - lastProgress;
- if (ticksSinceProgress >= NO_PROGRESS_TIMEOUT_NANOS) {
- LOG.error("Queue {} has not seen progress in {} seconds, failing all requests", this,
- TimeUnit.NANOSECONDS.toSeconds(ticksSinceProgress));
+ lock.lock();
+
+ final List<ConnectionEntry> poisonEntries;
+ final NoProgressException poisonCause;
+ try {
+ haveTimer = false;
+ final long now = currentTime();
+
+ LOG.debug("{}: running timer on {}", context.persistenceId(), this);
+
+ // The following line is only reliable when queue is not forwarding, but such state should not last long.
+ // FIXME: BUG-8422: this may not be accurate w.r.t. replayed entries
+ final long ticksSinceProgress = queue.ticksStalling(now);
+ if (ticksSinceProgress < context.config().getNoProgressTimeout()) {
+ // Requests are always scheduled in sequence, hence checking for timeout is relatively straightforward.
+ // Note we use also inquire about the delay, so we can re-schedule if needed, hence the unusual
+ // tri-state return convention.
+ final OptionalLong delay = lockedCheckTimeout(now);
+ if (delay == null) {
+ // We have timed out. There is no point in scheduling a timer
+ LOG.debug("{}: connection {} timed out", context.persistenceId(), this);
+ return lockedReconnect(current, new RuntimeRequestException("Backend connection timed out",
+ new TimeoutException()));
+ }
+
+ if (delay.isPresent()) {
+ // If there is new delay, schedule a timer
+ scheduleTimer(delay.orElseThrow());
+ } else {
+ LOG.debug("{}: not scheduling timeout on {}", context.persistenceId(), this);
+ }
- poison(new NoProgressException(ticksSinceProgress));
- current.removeConnection(this);
return current;
}
- }
- // Requests are always scheduled in sequence, hence checking for timeout is relatively straightforward.
- // Note we use also inquire about the delay, so we can re-schedule if needed, hence the unusual tri-state
- // return convention.
- final Optional<FiniteDuration> delay = checkTimeout(now);
- if (delay == null) {
- // We have timed out. There is no point in scheduling a timer
- return reconnectConnection(current);
- }
-
- if (delay.isPresent()) {
- // If there is new delay, schedule a timer
- scheduleTimer(delay.get());
+ LOG.error("Queue {} has not seen progress in {} seconds, failing all requests", this,
+ TimeUnit.NANOSECONDS.toSeconds(ticksSinceProgress));
+ poisonCause = new NoProgressException(ticksSinceProgress);
+ poisonEntries = lockedPoison(poisonCause);
+ current.removeConnection(this);
+ } finally {
+ lock.unlock();
}
+ poison(poisonEntries, poisonCause);
return current;
}
- boolean isEmpty() {
- return pending.isEmpty();
+ @VisibleForTesting
+ final OptionalLong checkTimeout(final long now) {
+ lock.lock();
+ try {
+ return lockedCheckTimeout(now);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ long backendSilentTicks(final long now) {
+ return now - lastReceivedTicks;
}
/*
*/
@SuppressFBWarnings(value = "NP_OPTIONAL_RETURN_NULL",
justification = "Returning null Optional is documented in the API contract.")
- final Optional<FiniteDuration> checkTimeout(final ConnectionEntry head, final long now) {
- if (head == null) {
- return Optional.empty();
+ @GuardedBy("lock")
+ private OptionalLong lockedCheckTimeout(final long now) {
+ if (queue.isEmpty()) {
+ LOG.debug("{}: connection {} is empty", context.persistenceId(), this);
+ return OptionalLong.empty();
}
- final long delay = head.getEnqueuedTicks() - now + REQUEST_TIMEOUT_NANOS;
- if (delay <= 0) {
- LOG.debug("Connection {} timed out", this);
+ final long backendSilentTicks = backendSilentTicks(now);
+ if (backendSilentTicks >= context.config().getBackendAlivenessTimerInterval()) {
+ LOG.debug("{}: Connection {} has not seen activity from backend for {} nanoseconds, timing out",
+ context.persistenceId(), this, backendSilentTicks);
return null;
}
- return Optional.of(FiniteDuration.apply(delay, TimeUnit.NANOSECONDS));
+ int tasksTimedOut = 0;
+ for (ConnectionEntry head = queue.peek(); head != null; head = queue.peek()) {
+ final long beenOpen = now - head.getEnqueuedTicks();
+ final long requestTimeout = context.config().getRequestTimeout();
+ if (beenOpen < requestTimeout) {
+ return OptionalLong.of(requestTimeout - beenOpen);
+ }
+
+ tasksTimedOut++;
+ queue.remove(now);
+ LOG.debug("{}: Connection {} timed out entry {}", context.persistenceId(), this, head);
+
+ timeoutEntry(head, beenOpen);
+ }
+
+ LOG.debug("Connection {} timed out {} tasks", this, tasksTimedOut);
+ if (tasksTimedOut != 0) {
+ queue.tryTransmit(now);
+ }
+
+ return OptionalLong.empty();
}
- /*
- * We are using tri-state return here to indicate one of three conditions:
- * - if there is no timeout to schedule, return Optional.empty()
- * - if there is a timeout to schedule, return a non-empty optional
- * - if this connections has timed out, return null
- */
- @SuppressFBWarnings(value = "NP_OPTIONAL_RETURN_NULL",
- justification = "Returning null Optional is documented in the API contract.")
- Optional<FiniteDuration> checkTimeout(final long now) {
- return checkTimeout(pending.peek(), now);
+ private void timeoutEntry(final ConnectionEntry entry, final long beenOpen) {
+ // Timeouts needs to be re-scheduled on actor thread because we are holding the lock on the current queue,
+ // which may be the tail of a successor chain. This is a problem if the callback attempts to send a request
+ // because that will attempt to lock the chain from the start, potentially causing a deadlock if there is
+ // a concurrent attempt to transmit.
+ context.executeInActor(current -> {
+ final double time = beenOpen * 1.0 / 1_000_000_000;
+ entry.complete(entry.getRequest().toRequestFailure(
+ new RequestTimeoutException(entry.getRequest() + " timed out after " + time
+ + " seconds. The backend for " + backendName + " is not available.")));
+ return current;
+ });
+ }
+
+ final void poison(final RequestException cause) {
+ final List<ConnectionEntry> entries;
+
+ lock.lock();
+ try {
+ entries = lockedPoison(cause);
+ } finally {
+ lock.unlock();
+ }
+
+ poison(entries, cause);
}
- static void poisonQueue(final Queue<? extends ConnectionEntry> queue, final RequestException cause) {
- for (ConnectionEntry e : queue) {
+ // Do not hold any locks while calling this
+ private static void poison(final Collection<? extends ConnectionEntry> entries, final RequestException cause) {
+ for (ConnectionEntry e : entries) {
final Request<?, ?> request = e.getRequest();
LOG.trace("Poisoning request {}", request, cause);
e.complete(request.toRequestFailure(cause));
}
- queue.clear();
}
- void poison(final RequestException cause) {
- poisoned = cause;
- poisonQueue(pending, cause);
+ @Holding("lock")
+ private List<ConnectionEntry> lockedPoison(final RequestException cause) {
+ poisoned = enrichPoison(cause);
+ return queue.poison();
+ }
+
+ RequestException enrichPoison(final RequestException ex) {
+ return ex;
}
@VisibleForTesting
return poisoned;
}
- abstract ClientActorBehavior<T> reconnectConnection(ClientActorBehavior<T> current);
+ void receiveResponse(final ResponseEnvelope<?> envelope) {
+ final long now = currentTime();
+ lastReceivedTicks = now;
+
+ final Optional<TransmittedConnectionEntry> maybeEntry;
+ lock.lock();
+ try {
+ maybeEntry = queue.complete(envelope, now);
+ } finally {
+ lock.unlock();
+ }
+
+ if (maybeEntry.isPresent()) {
+ final TransmittedConnectionEntry entry = maybeEntry.orElseThrow();
+ LOG.debug("Completing {} with {}", entry, envelope);
+ entry.complete(envelope.getMessage());
+ }
+ }
+
+ @Override
+ public final String toString() {
+ return addToStringAttributes(MoreObjects.toStringHelper(this).omitNullValues()).toString();
+ }
- abstract void receiveResponse(final ResponseEnvelope<?> envelope);
+ ToStringHelper addToStringAttributes(final ToStringHelper toStringHelper) {
+ return toStringHelper.add("client", context.getIdentifier()).add("cookie", cookie).add("poisoned", poisoned);
+ }
}