2 * Copyright (c) 2016 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.controller.cluster.access.client;
10 import akka.actor.ActorRef;
11 import com.google.common.annotations.VisibleForTesting;
12 import com.google.common.base.Preconditions;
13 import com.google.common.base.Verify;
14 import com.google.common.collect.Iterables;
15 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
16 import java.util.ArrayDeque;
17 import java.util.Deque;
18 import java.util.Iterator;
19 import java.util.Optional;
20 import java.util.Queue;
21 import javax.annotation.concurrent.NotThreadSafe;
22 import org.opendaylight.controller.cluster.access.concepts.Request;
23 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
24 import org.opendaylight.controller.cluster.access.concepts.RequestException;
25 import org.opendaylight.controller.cluster.access.concepts.Response;
26 import org.opendaylight.controller.cluster.access.concepts.ResponseEnvelope;
27 import org.slf4j.Logger;
28 import org.slf4j.LoggerFactory;
31 * This queue is internally split into two queues for performance reasons, both memory efficiency and copy
35 * Entries are always appended to the end, but then they are transmitted to the remote end and do not necessarily
36 * complete in the order in which they were sent -- hence the head of the queue does not increase linearly,
37 * but can involve spurious removals of non-head entries.
40 * For memory efficiency we want to pre-allocate both queues -- which points to ArrayDeque, but that is very
41 * inefficient when entries are removed from the middle. In the typical case we expect the number of in-flight
42 * entries to be an order of magnitude lower than the number of enqueued entries, hence the split.
45 * Note that in transient case of reconnect, when the backend gives us a lower number of maximum in-flight entries
46 * than the previous incarnation, we may end up still moving the pending queue -- but that is a very exceptional
47 * scenario, hence we consciously ignore it to keep the design relatively simple.
50 * This class is not thread-safe, as it is expected to be guarded by {@link AbstractClientConnection}.
52 * @author Robert Varga
55 abstract class TransmitQueue {
56 static final class Halted extends TransmitQueue {
57 Halted(final int targetDepth) {
62 int canTransmitCount(final int inflightSize) {
67 TransmittedConnectionEntry transmit(final ConnectionEntry entry, final long now) {
68 throw new UnsupportedOperationException("Attempted to transmit on a halted queue");
72 static final class Transmitting extends TransmitQueue {
73 private final BackendInfo backend;
74 private long nextTxSequence;
76 Transmitting(final int targetDepth, final BackendInfo backend) {
78 this.backend = Preconditions.checkNotNull(backend);
82 int canTransmitCount(final int inflightSize) {
83 return backend.getMaxMessages() - inflightSize;
87 TransmittedConnectionEntry transmit(final ConnectionEntry entry, final long now) {
88 final RequestEnvelope env = new RequestEnvelope(entry.getRequest().toVersion(backend.getVersion()),
89 backend.getSessionId(), nextTxSequence++);
91 final TransmittedConnectionEntry ret = new TransmittedConnectionEntry(entry, env.getSessionId(),
92 env.getTxSequence(), now);
93 backend.getActor().tell(env, ActorRef.noSender());
98 private static final Logger LOG = LoggerFactory.getLogger(TransmitQueue.class);
100 private final Deque<TransmittedConnectionEntry> inflight = new ArrayDeque<>();
101 private final Deque<ConnectionEntry> pending = new ArrayDeque<>();
102 private final ProgressTracker tracker;
103 private ReconnectForwarder successor;
105 TransmitQueue(final int targetDepth) {
106 tracker = new AveragingProgressTracker(targetDepth);
109 final Iterable<ConnectionEntry> asIterable() {
110 return Iterables.concat(inflight, pending);
113 final long ticksStalling(final long now) {
114 return tracker.ticksStalling(now);
117 final boolean hasSuccessor() {
118 return successor != null;
121 // If a matching request was found, this will track a task was closed.
122 final Optional<TransmittedConnectionEntry> complete(final ResponseEnvelope<?> envelope, final long now) {
123 Optional<TransmittedConnectionEntry> maybeEntry = findMatchingEntry(inflight, envelope);
124 if (maybeEntry == null) {
125 LOG.debug("Request for {} not found in inflight queue, checking pending queue", envelope);
126 maybeEntry = findMatchingEntry(pending, envelope);
129 if (maybeEntry == null || !maybeEntry.isPresent()) {
130 LOG.warn("No request matching {} found, ignoring response", envelope);
131 return Optional.empty();
134 final TransmittedConnectionEntry entry = maybeEntry.get();
135 tracker.closeTask(now, entry.getEnqueuedTicks(), entry.getTxTicks(), envelope.getExecutionTimeNanos());
137 // We have freed up a slot, try to transmit something
138 final int toSend = canTransmitCount(inflight.size());
139 if (toSend > 0 && !pending.isEmpty()) {
140 transmitEntries(toSend, now);
143 return Optional.of(entry);
146 private void transmitEntries(final int maxTransmit, final long now) {
147 for (int i = 0; i < maxTransmit; ++i) {
148 final ConnectionEntry e = pending.poll();
150 LOG.debug("Queue {} transmitted {} requests", this, i);
154 transmitEntry(e, now);
157 LOG.debug("Queue {} transmitted {} requests", this, maxTransmit);
160 private void transmitEntry(final ConnectionEntry entry, final long now) {
161 LOG.debug("Queue {} transmitting entry {}", entry);
162 // We are not thread-safe and are supposed to be externally-guarded,
163 // hence send-before-record should be fine.
164 // This needs to be revisited if the external guards are lowered.
165 inflight.addLast(transmit(entry, now));
169 * Enqueue an entry, possibly also transmitting it.
171 * @return Delay to be forced on the calling thread, in nanoseconds.
173 final long enqueue(final ConnectionEntry entry, final long now) {
174 if (successor != null) {
175 successor.forwardEntry(entry, now);
179 // XXX: we should place a guard against incorrect entry sequences:
180 // entry.getEnqueueTicks() should have non-negative difference from the last entry present in the queues
182 // Reserve an entry before we do anything that can fail
183 final long delay = tracker.openTask(now);
186 * This is defensive to make sure we do not do the wrong thing here and reorder messages if we ever happen
187 * to have available send slots and non-empty pending queue.
189 final int toSend = canTransmitCount(inflight.size());
191 LOG.trace("Queue is at capacity, delayed sending of request {}", entry.getRequest());
192 pending.addLast(entry);
196 if (pending.isEmpty()) {
197 transmitEntry(entry, now);
201 pending.addLast(entry);
202 transmitEntries(toSend, now);
207 * Return the number of entries which can be transmitted assuming the supplied in-flight queue size.
209 abstract int canTransmitCount(int inflightSize);
211 abstract TransmittedConnectionEntry transmit(ConnectionEntry entry, long now);
213 final boolean isEmpty() {
214 return inflight.isEmpty() && pending.isEmpty();
217 final ConnectionEntry peek() {
218 final ConnectionEntry ret = inflight.peek();
223 return pending.peek();
226 final void poison(final RequestException cause) {
227 poisonQueue(inflight, cause);
228 poisonQueue(pending, cause);
231 final void setForwarder(final ReconnectForwarder forwarder, final long now) {
232 Verify.verify(successor == null, "Successor {} already set on connection {}", successor, this);
233 successor = Preconditions.checkNotNull(forwarder);
234 LOG.debug("Connection {} superseded by {}, splicing queue", this, successor);
236 ConnectionEntry entry = inflight.poll();
237 while (entry != null) {
238 successor.forwardEntry(entry, now);
239 entry = inflight.poll();
242 entry = pending.poll();
243 while (entry != null) {
244 successor.forwardEntry(entry, now);
245 entry = pending.poll();
250 Deque<TransmittedConnectionEntry> getInflight() {
255 Deque<ConnectionEntry> getPending() {
260 * We are using tri-state return here to indicate one of three conditions:
261 * - if a matching entry is found, return an Optional containing it
262 * - if a matching entry is not found, but it makes sense to keep looking at other queues, return null
263 * - if a conflicting entry is encountered, indicating we should ignore this request, return an empty Optional
265 @SuppressFBWarnings(value = "NP_OPTIONAL_RETURN_NULL",
266 justification = "Returning null Optional is documented in the API contract.")
267 private static Optional<TransmittedConnectionEntry> findMatchingEntry(final Queue<? extends ConnectionEntry> queue,
268 final ResponseEnvelope<?> envelope) {
269 // Try to find the request in a queue. Responses may legally come back in a different order, hence we need
270 // to use an iterator
271 final Iterator<? extends ConnectionEntry> it = queue.iterator();
272 while (it.hasNext()) {
273 final ConnectionEntry e = it.next();
274 final Request<?, ?> request = e.getRequest();
275 final Response<?, ?> response = envelope.getMessage();
277 // First check for matching target, or move to next entry
278 if (!request.getTarget().equals(response.getTarget())) {
282 // Sanity-check logical sequence, ignore any out-of-order messages
283 if (request.getSequence() != response.getSequence()) {
284 LOG.debug("Expecting sequence {}, ignoring response {}", request.getSequence(), envelope);
285 return Optional.empty();
288 // Check if the entry has (ever) been transmitted
289 if (!(e instanceof TransmittedConnectionEntry)) {
290 return Optional.empty();
293 final TransmittedConnectionEntry te = (TransmittedConnectionEntry) e;
295 // Now check session match
296 if (envelope.getSessionId() != te.getSessionId()) {
297 LOG.debug("Expecting session {}, ignoring response {}", te.getSessionId(), envelope);
298 return Optional.empty();
300 if (envelope.getTxSequence() != te.getTxSequence()) {
301 LOG.warn("Expecting txSequence {}, ignoring response {}", te.getTxSequence(), envelope);
302 return Optional.empty();
305 LOG.debug("Completing request {} with {}", request, envelope);
307 return Optional.of(te);
313 private static void poisonQueue(final Queue<? extends ConnectionEntry> queue, final RequestException cause) {
314 for (ConnectionEntry e : queue) {
315 final Request<?, ?> request = e.getRequest();
316 LOG.trace("Poisoning request {}", request, cause);
317 e.complete(request.toRequestFailure(cause));