org.opendaylight.controller.cluster.access.client.AbstractClientConnection Maven / Gradle / Ivy
/*
* Copyright (c) 2016 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
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.MoreObjects;
import com.google.common.base.MoreObjects.ToStringHelper;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.util.Collection;
import java.util.List;
import java.util.Optional;
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 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. This class NOT thread-safe, not are its subclasses expected to be thread-safe.
*
* @author Robert Varga
*/
public abstract class AbstractClientConnection {
private static final Logger LOG = LoggerFactory.getLogger(AbstractClientConnection.class);
/*
* 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;
/**
* Time reference when we saw any activity from the backend.
*/
private long lastReceivedTicks;
private volatile RequestException poisoned;
// Private constructor to avoid code duplication.
private AbstractClientConnection(final AbstractClientConnection 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 AbstractClientConnection 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 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 @NonNull ClientActorContext context() {
return context;
}
public final @NonNull Long cookie() {
return cookie;
}
public final @NonNull ActorRef localActor() {
return context.self();
}
public final long currentTime() {
return context.ticker().read();
}
/**
* Send a request to the backend and invoke a specified callback when it finishes. This method is safe to invoke
* from any thread.
*
* 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> 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.
*
*
* 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 enqueueRequest(final Request request, final Consumer> callback,
final long enqueuedTicks) {
enqueueEntry(new ConnectionEntry(request, callback, enqueuedTicks), currentTime());
}
private long enqueueOrForward(final ConnectionEntry entry, final long now) {
lock.lock();
try {
commonEnqueue(entry, now);
return queue.enqueueOrForward(entry, now);
} finally {
lock.unlock();
}
}
/**
* 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();
}
}
@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);
}
}
// To be called from ClientActorBehavior on ConnectedClientConnection after entries are replayed.
final void cancelDebt() {
queue.cancelDebt(currentTime());
}
public abstract Optional getBackendInfo();
final Collection 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());
}
@Holding("lock")
abstract ClientActorBehavior lockedReconnect(ClientActorBehavior 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);
}
}
final ClientActorBehavior reconnect(final ClientActorBehavior current, final RequestException cause) {
lock.lock();
try {
return lockedReconnect(current, cause);
} finally {
lock.unlock();
}
}
/**
* Schedule a timer to fire on the actor thread after a delay.
*
* @param delay Delay, in nanoseconds
*/
@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 #DEFAULT_NO_PROGRESS_TIMEOUT_NANOS} nanoseconds, it will be aborted.
*
* @param current Current behavior
* @return Next behavior to use
*/
@VisibleForTesting
final ClientActorBehavior runTimer(final ClientActorBehavior current) {
lock.lock();
final List 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);
}
return current;
}
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;
}
@VisibleForTesting
final OptionalLong checkTimeout(final long now) {
lock.lock();
try {
return lockedCheckTimeout(now);
} finally {
lock.unlock();
}
}
long backendSilentTicks(final long now) {
return now - lastReceivedTicks;
}
/*
* 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.")
@GuardedBy("lock")
private OptionalLong lockedCheckTimeout(final long now) {
if (queue.isEmpty()) {
LOG.debug("{}: connection {} is empty", context.persistenceId(), this);
return OptionalLong.empty();
}
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;
}
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();
}
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 entries;
lock.lock();
try {
entries = lockedPoison(cause);
} finally {
lock.unlock();
}
poison(entries, cause);
}
// Do not hold any locks while calling this
private static void poison(final Collection entries, final RequestException cause) {
for (ConnectionEntry e : entries) {
final Request request = e.getRequest();
LOG.trace("Poisoning request {}", request, cause);
e.complete(request.toRequestFailure(cause));
}
}
@Holding("lock")
private List lockedPoison(final RequestException cause) {
poisoned = enrichPoison(cause);
return queue.poison();
}
RequestException enrichPoison(final RequestException ex) {
return ex;
}
@VisibleForTesting
final RequestException poisoned() {
return poisoned;
}
void receiveResponse(final ResponseEnvelope envelope) {
final long now = currentTime();
lastReceivedTicks = now;
final Optional 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();
}
ToStringHelper addToStringAttributes(final ToStringHelper toStringHelper) {
return toStringHelper.add("client", context.getIdentifier()).add("cookie", cookie).add("poisoned", poisoned);
}
}