*/
package org.opendaylight.yangtools.util.concurrent;
-import static com.google.common.base.Preconditions.checkArgument;
-import static java.util.Objects.requireNonNull;
-
import com.google.common.collect.ImmutableList;
-import java.util.ArrayDeque;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Queue;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.Executor;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.locks.Condition;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
-import java.util.stream.Collectors;
-import org.checkerframework.checker.lock.qual.GuardedBy;
import org.eclipse.jdt.annotation.NonNull;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
/**
- * This class manages queuing and dispatching notifications for multiple listeners concurrently.
- * Notifications are queued on a per-listener basis and dispatched serially to each listener via an
- * {@link Executor}.
+ * {@inheritDoc}
*
- * <p>This class optimizes its memory footprint by only allocating and maintaining a queue and executor
- * task for a listener when there are pending notifications. On the first notification(s), a queue
- * is created and a task is submitted to the executor to dispatch the queue to the associated
- * listener. Any subsequent notifications that occur before all previous notifications have been
- * dispatched are appended to the existing queue. When all notifications have been dispatched, the
- * queue and task are discarded.
+ * <p>
+ * This class is pessimistic about listener type and uses identity mapping for comparing them. This is defensive versus
+ * reused objects, maintaining semantics. This may not always be intended, for example if {@code L} is a {@code String}
+ * which is being dynamically determined. In that case we do not want to use identity, but equality, as otherwise
+ * the caller is forced to use {@link String#intern()} -- leading to interning in lookup, which is absolutely
+ * unnecessary. In such use cases, use {@link EqualityQueuedNotificationManager} instead.
*
* @author Thomas Pantelis
- *
- * @param <L> the listener type
- * @param <N> the notification type
*/
-public final class QueuedNotificationManager<L, N> implements NotificationManager<L, N> {
+public final class QueuedNotificationManager<L, N> extends IdentityQueuedNotificationManager<L, N> {
@FunctionalInterface
public interface BatchedInvoker<L, N> {
/**
* @param listener the listener to invoke
* @param notifications notifications to send
*/
- void invokeListener(@NonNull L listener, @NonNull Collection<? extends N> notifications);
+ void invokeListener(@NonNull L listener, @NonNull ImmutableList<N> notifications);
}
- private static final Logger LOG = LoggerFactory.getLogger(QueuedNotificationManager.class);
-
- /**
- * Caps the maximum number of attempts to offer notification to a particular listener. Each
- * attempt window is 1 minute, so an offer times out after roughly 10 minutes.
- */
- private static final int MAX_NOTIFICATION_OFFER_MINUTES = 10;
- private static final long GIVE_UP_NANOS = TimeUnit.MINUTES.toNanos(MAX_NOTIFICATION_OFFER_MINUTES);
- private static final long TASK_WAIT_NANOS = TimeUnit.MILLISECONDS.toNanos(10);
-
- private final ConcurrentMap<ListenerKey<L>, NotificationTask> listenerCache = new ConcurrentHashMap<>();
- private final @NonNull BatchedInvoker<L, N> listenerInvoker;
- private final @NonNull Executor executor;
- private final @NonNull String name;
- private final int maxQueueCapacity;
-
- private QueuedNotificationManager(final @NonNull Executor executor,
- final @NonNull BatchedInvoker<L, N> listenerInvoker, final int maxQueueCapacity,
- final @NonNull String name) {
- checkArgument(maxQueueCapacity > 0, "Invalid maxQueueCapacity %s must be > 0", maxQueueCapacity);
- this.executor = requireNonNull(executor);
- this.listenerInvoker = requireNonNull(listenerInvoker);
- this.maxQueueCapacity = maxQueueCapacity;
- this.name = requireNonNull(name);
+ QueuedNotificationManager(final @NonNull Executor executor, final @NonNull BatchedInvoker<L, N> listenerInvoker,
+ final int maxQueueCapacity, final @NonNull String name) {
+ super(name, executor, maxQueueCapacity, listenerInvoker);
}
/**
final @NonNull String name) {
return new QueuedNotificationManager<>(executor, listenerInvoker, maxQueueCapacity, name);
}
-
- /**
- * Returns the maximum listener queue capacity.
- */
- public int getMaxQueueCapacity() {
- return maxQueueCapacity;
- }
-
- /**
- * Returns the {@link Executor} to used for notification tasks.
- */
- public @NonNull Executor getExecutor() {
- return executor;
- }
-
- /* (non-Javadoc)
- * @see org.opendaylight.yangtools.util.concurrent.NotificationManager#addNotification(L, N)
- */
- @Override
- public void submitNotification(final L listener, final N notification) {
- if (notification != null) {
- submitNotifications(listener, Collections.singletonList(notification));
- }
- }
-
- /* (non-Javadoc)
- * @see org.opendaylight.yangtools.util.concurrent.NotificationManager#submitNotifications(L, java.util.Collection)
- */
- @Override
- public void submitNotifications(final L listener, final Iterable<N> notifications) {
-
- if (notifications == null || listener == null) {
- return;
- }
-
- LOG.trace("{}: submitNotifications for listener {}: {}", name, listener, notifications);
-
- final ListenerKey<L> key = new ListenerKey<>(listener);
-
- // Keep looping until we are either able to add a new NotificationTask or are able to
- // add our notifications to an existing NotificationTask. Eventually one or the other
- // will occur.
- try {
- Iterator<N> it = notifications.iterator();
-
- while (true) {
- NotificationTask task = listenerCache.get(key);
- if (task == null) {
- // No task found, try to insert a new one
- final NotificationTask newTask = new NotificationTask(key, it);
- task = listenerCache.putIfAbsent(key, newTask);
- if (task == null) {
- // We were able to put our new task - now submit it to the executor and
- // we're done. If it throws a RejectedExecutionException, let that propagate
- // to the caller.
- runTask(listener, newTask);
- break;
- }
-
- // We have a racing task, hence we can continue, but we need to refresh our iterator from
- // the task.
- it = newTask.recoverItems();
- }
-
- final boolean completed = task.submitNotifications(it);
- if (!completed) {
- // Task is indicating it is exiting before it has consumed all the items and is exiting. Rather
- // than spinning on removal, we try to replace it.
- final NotificationTask newTask = new NotificationTask(key, it);
- if (listenerCache.replace(key, task, newTask)) {
- runTask(listener, newTask);
- break;
- }
-
- // We failed to replace the task, hence we need retry. Note we have to recover the items to be
- // published from the new task.
- it = newTask.recoverItems();
- LOG.debug("{}: retrying task queueing for {}", name, listener);
- continue;
- }
-
- // All notifications have either been delivered or we have timed out and warned about the ones we
- // have failed to deliver. In any case we are done here.
- break;
- }
- } catch (InterruptedException e) {
- // We were interrupted trying to offer to the listener's queue. Somebody's probably
- // telling us to quit.
- LOG.warn("{}: Interrupted trying to add to {} listener's queue", name, listener);
- }
-
- LOG.trace("{}: submitNotifications done for listener {}", name, listener);
- }
-
- /**
- * Returns {@link ListenerNotificationQueueStats} instances for each current listener
- * notification task in progress.
- */
- public List<ListenerNotificationQueueStats> getListenerNotificationQueueStats() {
- return listenerCache.values().stream().map(t -> new ListenerNotificationQueueStats(t.listenerKey.toString(),
- t.size())).collect(Collectors.toList());
- }
-
- private void runTask(final L listener, final NotificationTask task) {
- LOG.debug("{}: Submitting NotificationTask for listener {}", name, listener);
- executor.execute(task);
- }
-
- /**
- * Used as the listenerCache map key. We key by listener reference identity hashCode/equals.
- * Since we don't know anything about the listener class implementations and we're mixing
- * multiple listener class instances in the same map, this avoids any potential issue with an
- * equals implementation that just blindly casts the other Object to compare instead of checking
- * for instanceof.
- */
- private static final class ListenerKey<L> {
- private final @NonNull L listener;
-
- ListenerKey(final L listener) {
- this.listener = requireNonNull(listener);
- }
-
- @NonNull L getListener() {
- return listener;
- }
-
- @Override
- public int hashCode() {
- return System.identityHashCode(listener);
- }
-
- @Override
- public boolean equals(final Object obj) {
- return obj == this || obj instanceof ListenerKey<?> && listener == ((ListenerKey<?>) obj).listener;
- }
-
- @Override
- public String toString() {
- return listener.toString();
- }
- }
-
- /**
- * Executor task for a single listener that queues notifications and sends them serially to the
- * listener.
- */
- private class NotificationTask implements Runnable {
- private final Lock lock = new ReentrantLock();
- private final Condition notEmpty = lock.newCondition();
- private final Condition notFull = lock.newCondition();
- private final @NonNull ListenerKey<L> listenerKey;
-
- @GuardedBy("lock")
- private final Queue<N> queue = new ArrayDeque<>();
- @GuardedBy("lock")
- private boolean exiting;
-
- NotificationTask(final @NonNull ListenerKey<L> listenerKey, final @NonNull Iterator<N> notifications) {
- this.listenerKey = requireNonNull(listenerKey);
- while (notifications.hasNext()) {
- queue.add(notifications.next());
- }
- }
-
- @NonNull Iterator<N> recoverItems() {
- // This violates @GuardedBy annotation, but is invoked only when the task is not started and will never
- // get started, hence this is safe.
- return queue.iterator();
- }
-
- int size() {
- lock.lock();
- try {
- return queue.size();
- } finally {
- lock.unlock();
- }
- }
-
- boolean submitNotifications(final @NonNull Iterator<N> notifications) throws InterruptedException {
- final long start = System.nanoTime();
- final long deadline = start + GIVE_UP_NANOS;
-
- lock.lock();
- try {
- // Lock may have blocked for some time, we need to take that into account. We may have exceedded
- // the deadline, but that is unlikely and even in that case we can make some progress without further
- // blocking.
- long canWait = deadline - System.nanoTime();
-
- while (true) {
- // Check the exiting flag - if true then #run is in the process of exiting so return
- // false to indicate such. Otherwise, offer the notifications to the queue.
- if (exiting) {
- return false;
- }
-
- final int avail = maxQueueCapacity - queue.size();
- if (avail <= 0) {
- if (canWait <= 0) {
- LOG.warn("{}: Failed to offer notifications {} to the queue for listener {}. Exceeded"
- + "maximum allowable time of {} minutes; the listener is likely in an unrecoverable"
- + "state (deadlock or endless loop). ", name, ImmutableList.copyOf(notifications),
- listenerKey, MAX_NOTIFICATION_OFFER_MINUTES);
- return true;
- }
-
- canWait = notFull.awaitNanos(canWait);
- continue;
- }
-
- for (int i = 0; i < avail; ++i) {
- if (!notifications.hasNext()) {
- notEmpty.signal();
- return true;
- }
-
- queue.add(notifications.next());
- }
- }
- } finally {
- lock.unlock();
- }
- }
-
- @GuardedBy("lock")
- private boolean waitForQueue() {
- long timeout = TASK_WAIT_NANOS;
-
- while (queue.isEmpty()) {
- if (timeout <= 0) {
- return false;
- }
-
- try {
- timeout = notEmpty.awaitNanos(timeout);
- } catch (InterruptedException e) {
- // The executor is probably shutting down so log as debug.
- LOG.debug("{}: Interrupted trying to remove from {} listener's queue", name, listenerKey);
- return false;
- }
- }
-
- return true;
- }
-
- @Override
- public void run() {
- try {
- // Loop until we've dispatched all the notifications in the queue.
- while (true) {
- final @NonNull Collection<N> notifications;
-
- lock.lock();
- try {
- if (!waitForQueue()) {
- exiting = true;
- break;
- }
-
- // Splice the entire queue
- notifications = ImmutableList.copyOf(queue);
- queue.clear();
-
- notFull.signalAll();
- } finally {
- lock.unlock();
- }
-
- invokeListener(notifications);
- }
- } finally {
- // We're exiting, gracefully or not - either way make sure we always remove
- // ourselves from the cache.
- listenerCache.remove(listenerKey, this);
- }
- }
-
- @SuppressWarnings("checkstyle:illegalCatch")
- private void invokeListener(final @NonNull Collection<N> notifications) {
- LOG.debug("{}: Invoking listener {} with notification: {}", name, listenerKey, notifications);
- try {
- listenerInvoker.invokeListener(listenerKey.getListener(), notifications);
- } catch (Exception e) {
- // We'll let a RuntimeException from the listener slide and keep sending any remaining notifications.
- LOG.error("{}: Error notifying listener {} with {}", name, listenerKey, notifications, e);
- }
- }
- }
}
Code Review / yangtools.git / blobdiff