* 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.yangtools.util.concurrent;
-import java.util.Arrays;
-import java.util.concurrent.BlockingQueue;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
+import com.google.common.collect.ImmutableList;
import java.util.concurrent.Executor;
-import java.util.concurrent.LinkedBlockingQueue;
-import java.util.concurrent.RejectedExecutionException;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
-
-import javax.annotation.concurrent.GuardedBy;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import com.google.common.base.Preconditions;
+import org.eclipse.jdt.annotation.NonNull;
/**
- * 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.
+ * 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 class QueuedNotificationManager<L,N> implements NotificationManager<L,N> {
-
- /**
- * Interface implemented by clients that does the work of invoking listeners with notifications.
- *
- * @author Thomas Pantelis
- *
- * @param <L> the listener type
- * @param <N> the notification type
- */
- public interface Invoker<L,N> {
-
+public final class QueuedNotificationManager<L, N> extends IdentityQueuedNotificationManager<L, N> {
+ @FunctionalInterface
+ public interface BatchedInvoker<L, N> {
/**
* Called to invoke a listener with a notification.
*
* @param listener the listener to invoke
- * @param notification the notification to send
+ * @param notifications notifications to send
*/
- void invokeListener( L listener, N notification );
+ void invokeListener(@NonNull L listener, @NonNull ImmutableList<N> notifications);
}
- private static final Logger LOG = LoggerFactory.getLogger( QueuedNotificationManager.class );
-
- private final Executor executor;
- private final Invoker<L,N> listenerInvoker;
-
- private final ConcurrentMap<ListenerKey<L>,NotificationTask>
- listenerCache = new ConcurrentHashMap<>();
-
- private final String name;
- private final int maxQueueCapacity;
+ QueuedNotificationManager(final @NonNull Executor executor, final @NonNull BatchedInvoker<L, N> listenerInvoker,
+ final int maxQueueCapacity, final @NonNull String name) {
+ super(name, executor, maxQueueCapacity, listenerInvoker);
+ }
/**
- * Constructor.
+ * Create a new notification manager.
*
* @param executor the {@link Executor} to use for notification tasks
- * @param listenerInvoker the {@link Invoker} to use for invoking listeners
+ * @param listenerInvoker the {@link BatchedInvoker} to use for invoking listeners
* @param maxQueueCapacity the capacity of each listener queue
* @param name the name of this instance for logging info
*/
- public QueuedNotificationManager( Executor executor, Invoker<L,N> listenerInvoker,
- int maxQueueCapacity, String name ) {
- this.executor = Preconditions.checkNotNull( executor );
- this.listenerInvoker = Preconditions.checkNotNull( listenerInvoker );
- Preconditions.checkArgument( maxQueueCapacity > 0, "maxQueueCapacity must be > 0 " );
- this.maxQueueCapacity = maxQueueCapacity;
- this.name = Preconditions.checkNotNull( name );
- }
-
- /* (non-Javadoc)
- * @see org.opendaylight.yangtools.util.concurrent.NotificationManager#addNotification(L, N)
- */
- @Override
- public void submitNotification( final L listener, final N notification )
- throws RejectedExecutionException {
-
- if( notification == null ) {
- return;
- }
-
- submitNotifications( listener, Arrays.asList( 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 )
- throws RejectedExecutionException {
-
- if( notifications == null || listener == null ) {
- return;
- }
-
- if( LOG.isTraceEnabled() ) {
- LOG.trace( "{}: submitNotifications for listener {}: {}",
- name, listener.getClass(), notifications );
- }
-
- ListenerKey<L> key = new ListenerKey<>( listener );
- NotificationTask newNotificationTask = null;
-
- // 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 {
- while( true ) {
- NotificationTask existingTask = listenerCache.get( key );
-
- if( existingTask == null || !existingTask.submitNotifications( notifications ) ) {
-
- // Either there's no existing task or we couldn't add our notifications to the
- // existing one because it's in the process of exiting and removing itself from
- // the cache. Either way try to put a new task in the cache. If we can't put
- // then either the existing one is still there and hasn't removed itself quite
- // yet or some other concurrent thread beat us to the put although this method
- // shouldn't be called concurrently for the same listener as that would violate
- // notification ordering. In any case loop back up and try again.
-
- if( newNotificationTask == null ) {
- newNotificationTask = new NotificationTask( key, notifications );
- }
-
- existingTask = listenerCache.putIfAbsent( key, newNotificationTask );
- if( existingTask == null ) {
-
- // We were able to put our new task - now submit it to the executor and
- // we're done. If it throws a RejectedxecutionException, let that propagate
- // to the caller.
-
- LOG.debug( "{}: Submitting NotificationTask for listener {}",
- name, listener.getClass() );
-
- executor.execute( newNotificationTask );
- break;
- }
- } else {
-
- // We were able to add our notifications to an existing task so we're done.
-
- break;
- }
- }
- } catch( InterruptedException e ) {
-
- // We were interrupted trying to offer to the listener's queue. Somebody's probably
- // telling us to quit.
-
- LOG.debug( "{}: Interrupted trying to add to {} listener's queue",
- name, listener.getClass() );
- }
-
- if( LOG.isTraceEnabled() ) {
- LOG.trace( "{}: submitNotifications dine for listener {}",
- name, listener.getClass() );
- }
- }
-
- /**
- * 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 class ListenerKey<L> {
-
- private final L listener;
-
- public ListenerKey( L listener ) {
- this.listener = listener;
- }
-
- L getListener() {
- return listener;
- }
-
- @Override
- public int hashCode() {
- return System.identityHashCode( listener );
- }
-
- @Override
- public boolean equals( Object obj ) {
- ListenerKey<?> other = (ListenerKey<?>) obj;
- return listener == other.listener;
- }
- }
-
- /**
- * Executor task for a single listener that queues notifications and sends them serially to the
- * listener.
- */
- private class NotificationTask implements Runnable {
-
- private final BlockingQueue<N> notificationQueue;
-
- private volatile boolean done = false;
-
- @GuardedBy("queuingLock")
- private boolean queuedNotifications = false;
-
- private final Lock queuingLock = new ReentrantLock();
-
- private final ListenerKey<L> listenerKey;
-
- NotificationTask( ListenerKey<L> listenerKey, Iterable<N> notifications ) {
-
- this.listenerKey = listenerKey;
- this.notificationQueue = new LinkedBlockingQueue<>( maxQueueCapacity );
-
- for( N notification: notifications ) {
- this.notificationQueue.add( notification );
- }
- }
-
- boolean submitNotifications( Iterable<N> notifications ) throws InterruptedException {
-
- queuingLock.lock();
- try {
-
- // Check the done 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( done ) {
- return false;
- }
-
- for( N notification: notifications ) {
-
- while( true ) {
-
- // Try to offer for up to a minute and log a message if it times out.
-
- // FIXME: we loop forever to guarantee delivery however this leaves it open
- // for 1 rogue listener to bring everyone to a halt. Another option is to
- // limit the tries and give up after a while and drop the notification.
- // Given a reasonably large queue capacity and long timeout, if we still
- // can't queue then most likely the listener is an unrecoverable state
- // (deadlock or endless loop).
-
- if( LOG.isDebugEnabled() ) {
- LOG.debug( "{}: Offering notification to the queue for listener {}: {}",
- name, listenerKey.getListener().getClass(), notification );
- }
-
- if( notificationQueue.offer( notification, 1, TimeUnit.MINUTES ) ) {
- break;
- }
-
- LOG.warn(
- "{}: Timed out trying to offer a notification to the queue for listener {}." +
- "The queue has reached its capacity of {}",
- name, listenerKey.getListener().getClass(), maxQueueCapacity );
- }
- }
-
- // Set the queuedNotifications flag to tell #run that we've just queued
- // notifications and not to exit yet, even if it thinks the queue is empty at this
- // point.
-
- queuedNotifications = true;
-
- } finally {
- queuingLock.unlock();
- }
-
- return true;
- }
-
- @Override
- public void run() {
-
- try {
- // Loop until we've dispatched all the notifications in the queue.
-
- while( true ) {
-
- // Get the notification at the head of the queue, waiting a little bit for one
- // to get offered.
-
- N notification = notificationQueue.poll( 10, TimeUnit.MILLISECONDS );
- if( notification == null ) {
-
- // The queue is empty - try to get the queuingLock. If we can't get the lock
- // then #submitNotifications is in the process of offering to the queue so
- // we'll loop back up and poll the queue again.
-
- if( queuingLock.tryLock() ) {
- try {
-
- // Check the queuedNotifications flag to see if #submitNotifications
- // has offered new notification(s) to the queue. If so, loop back up
- // and poll the queue again. Otherwise set done to true and exit.
- // Once we set the done flag and unlock, calls to
- // #submitNotifications will fail and a new task will be created.
-
- if( !queuedNotifications ) {
- done = true;
- break;
- }
-
- // Clear the queuedNotifications flag so we'll try to exit the next
- // time through the loop when the queue is empty.
-
- queuedNotifications = false;
-
- } finally {
- queuingLock.unlock();
- }
- }
- }
-
- notifyListener( notification );
- }
- } 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.getListener().getClass() );
- } finally {
-
- // We're exiting, gracefully or not - either way make sure we always remove
- // ourselves from the cache.
-
- listenerCache.remove( listenerKey );
- }
- }
-
- private void notifyListener( N notification ) {
-
- if( notification == null ) {
- return;
- }
-
- try {
-
- if( LOG.isDebugEnabled() ) {
- LOG.debug( "{}: Invoking listener {} with notification: {}",
- name, listenerKey.getListener().getClass(), notification );
- }
-
- listenerInvoker.invokeListener( listenerKey.getListener(), notification );
-
- } catch( RuntimeException e ) {
-
- // We'll let a RuntimeException from the listener slide and keep sending any
- // remaining notifications.
-
- LOG.error( String.format( "%1$s: Error notifying listener %2$s", name,
- listenerKey.getListener().getClass() ), e );
-
- } catch( Error e ) {
-
- // A JVM Error is severe - best practice is to throw them up the chain. Set done to
- // true so no new notifications can be added to this task as we're about to bail.
-
- done = true;
- throw e;
- }
- }
+ public static <L, N> QueuedNotificationManager<L, N> create(final @NonNull Executor executor,
+ final@NonNull BatchedInvoker<L, N> listenerInvoker, final int maxQueueCapacity,
+ final @NonNull String name) {
+ return new QueuedNotificationManager<>(executor, listenerInvoker, maxQueueCapacity, name);
}
}
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