package org.opendaylight.yangtools.util.concurrent;
-import java.util.Arrays;
+import com.google.common.base.Preconditions;
+import java.util.Collections;
+import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
-
+import java.util.stream.Collectors;
import javax.annotation.concurrent.GuardedBy;
-
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
-import com.google.common.base.Preconditions;
-
/**
* 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}.
- * <p>
- * This class optimizes its memory footprint by only allocating and maintaining a queue and executor
+ *
+ * <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
* @param <L> the listener type
* @param <N> the notification type
*/
-public class QueuedNotificationManager<L,N> implements NotificationManager<L,N> {
+public class QueuedNotificationManager<L, N> implements NotificationManager<L, N> {
/**
* Interface implemented by clients that does the work of invoking listeners with notifications.
* @param <L> the listener type
* @param <N> the notification type
*/
- public interface Invoker<L,N> {
+ public interface Invoker<L, N> {
/**
* Called to invoke a listener with a notification.
* @param listener the listener to invoke
* @param notification the notification to send
*/
- void invokeListener( L listener, N notification );
+ void invokeListener(L listener, N notification);
}
- private static final Logger LOG = LoggerFactory.getLogger( QueuedNotificationManager.class );
+ 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<>();
+ /**
+ * 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_ATTEMPTS = 10;
+ private final ConcurrentMap<ListenerKey<L>, NotificationTask> listenerCache = new ConcurrentHashMap<>();
+ private final Invoker<L, N> listenerInvoker;
+ private final Executor executor;
private final String name;
private final int maxQueueCapacity;
* @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 " );
+ public QueuedNotificationManager(final Executor executor, final Invoker<L, N> listenerInvoker,
+ final int maxQueueCapacity, final String name) {
+ Preconditions.checkArgument(maxQueueCapacity > 0, "Invalid maxQueueCapacity %s must be > 0", maxQueueCapacity);
+ this.executor = Preconditions.checkNotNull(executor);
+ this.listenerInvoker = Preconditions.checkNotNull(listenerInvoker);
this.maxQueueCapacity = maxQueueCapacity;
- this.name = Preconditions.checkNotNull( name );
+ 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;
+ public void submitNotification(final L listener, final N notification) throws RejectedExecutionException {
+ if (notification != null) {
+ submitNotifications(listener, Collections.singletonList(notification));
}
-
- 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 )
+ public void submitNotifications(final L listener, final Iterable<N> notifications)
throws RejectedExecutionException {
- if( notifications == null || listener == null ) {
+ if (notifications == null || listener == null) {
return;
}
- if( LOG.isTraceEnabled() ) {
- LOG.trace( "{}: submitNotifications for listener {}: {}",
- name, listener.getClass(), notifications );
- }
+ LOG.trace("{}: submitNotifications for listener {}: {}", name, listener, notifications);
- ListenerKey<L> key = new ListenerKey<>( listener );
- NotificationTask newNotificationTask = null;
+ 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 {
- 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 {
+ NotificationTask newNotificationTask = null;
+ while (true) {
+ final NotificationTask existingTask = listenerCache.get(key);
+ if (existingTask != null && existingTask.submitNotifications(notifications)) {
// We were able to add our notifications to an existing task so we're done.
+ break;
+ }
+
+ // 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);
+ }
+ final NotificationTask oldTask = listenerCache.putIfAbsent(key, newNotificationTask);
+ if (oldTask == 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);
+ executor.execute(newNotificationTask);
break;
}
- }
- } catch( InterruptedException e ) {
+ LOG.debug("{}: retrying task queueing for {}", name, listener);
+ }
+ } 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() );
+ LOG.warn("{}: Interrupted trying to add to {} listener's queue", name, listener);
}
- if( LOG.isTraceEnabled() ) {
- LOG.trace( "{}: submitNotifications dine for listener {}",
- name, listener.getClass() );
- }
+ LOG.trace("{}: submitNotifications dine 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.notificationQueue.size())).collect(Collectors.toList());
+ }
+
+ /**
+ * Returns the maximum listener queue capacity.
+ */
+ public int getMaxQueueCapacity() {
+ return maxQueueCapacity;
+ }
+
+ /**
+ * Returns the {@link Executor} to used for notification tasks.
+ */
+ public Executor getExecutor() {
+ return executor;
}
/**
* equals implementation that just blindly casts the other Object to compare instead of checking
* for instanceof.
*/
- private static class ListenerKey<L> {
-
+ private static final class ListenerKey<L> {
private final L listener;
- public ListenerKey( L listener ) {
- this.listener = listener;
+ ListenerKey(final L listener) {
+ this.listener = Preconditions.checkNotNull(listener);
}
L getListener() {
@Override
public int hashCode() {
- return System.identityHashCode( listener );
+ return System.identityHashCode(listener);
+ }
+
+ @Override
+ public boolean equals(final Object obj) {
+ if (obj == this) {
+ return true;
+ }
+ return (obj instanceof ListenerKey<?>) && listener == ((ListenerKey<?>) obj).listener;
}
@Override
- public boolean equals( Object obj ) {
- ListenerKey<?> other = (ListenerKey<?>) obj;
- return listener == other.listener;
+ public String toString() {
+ return listener.toString();
}
}
* listener.
*/
private class NotificationTask implements Runnable {
-
+ private final Lock queuingLock = new ReentrantLock();
private final BlockingQueue<N> notificationQueue;
-
- private volatile boolean done = false;
+ private final ListenerKey<L> listenerKey;
@GuardedBy("queuingLock")
private boolean queuedNotifications = false;
+ private volatile boolean done = false;
- private final Lock queuingLock = new ReentrantLock();
+ NotificationTask(final ListenerKey<L> listenerKey, final Iterable<N> notifications) {
+ this.listenerKey = Preconditions.checkNotNull(listenerKey);
+ this.notificationQueue = new LinkedBlockingQueue<>(maxQueueCapacity);
- private final ListenerKey<L> listenerKey;
+ for (N notification: notifications) {
+ this.notificationQueue.add(notification);
+ }
+ }
- NotificationTask( ListenerKey<L> listenerKey, Iterable<N> notifications ) {
+ @GuardedBy("queuingLock")
+ private void publishNotification(final N notification) throws InterruptedException {
+ // The offer is attempted for up to 10 minutes, with a status message printed each minute
+ for (int notificationOfferAttempts = 0;
+ notificationOfferAttempts < MAX_NOTIFICATION_OFFER_ATTEMPTS; notificationOfferAttempts++) {
- this.listenerKey = listenerKey;
- this.notificationQueue = new LinkedBlockingQueue<>( maxQueueCapacity );
+ // Try to offer for up to a minute and log a message if it times out.
+ LOG.debug("{}: Offering notification to the queue for listener {}: {}", name, listenerKey,
+ notification);
- for( N notification: notifications ) {
- this.notificationQueue.add( notification );
+ if (notificationQueue.offer(notification, 1, TimeUnit.MINUTES)) {
+ return;
+ }
+
+ LOG.warn("{}: Timed out trying to offer a notification to the queue for listener {} "
+ + "on attempt {} of {}. The queue has reached its capacity of {}", name, listenerKey,
+ notificationOfferAttempts, MAX_NOTIFICATION_OFFER_ATTEMPTS, maxQueueCapacity);
}
+
+ LOG.warn("{}: Failed to offer a notification to the queue for listener {}. Exceeded max allowable attempts"
+ + " of {} in {} minutes; the listener is likely in an unrecoverable state (deadlock or endless"
+ + " loop).", name, listenerKey, MAX_NOTIFICATION_OFFER_ATTEMPTS, MAX_NOTIFICATION_OFFER_ATTEMPTS);
}
- boolean submitNotifications( Iterable<N> notifications ) throws InterruptedException {
+ boolean submitNotifications(final 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 ) {
+ 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 );
- }
+ for (N notification : notifications) {
+ publishNotification(notification);
}
// Set the queuedNotifications flag to tell #run that we've just queued
// point.
queuedNotifications = true;
-
} finally {
queuingLock.unlock();
}
@Override
public void run() {
-
try {
// Loop until we've dispatched all the notifications in the queue.
- while( true ) {
-
+ 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 ) {
+ final 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() ) {
+ if (queuingLock.tryLock()) {
try {
// Check the queuedNotifications flag to see if #submitNotifications
// Once we set the done flag and unlock, calls to
// #submitNotifications will fail and a new task will be created.
- if( !queuedNotifications ) {
+ if (!queuedNotifications) {
done = true;
break;
}
}
}
- notifyListener( notification );
+ notifyListener(notification);
}
- } catch( InterruptedException e ) {
-
+ } 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() );
+ LOG.debug("{}: Interrupted trying to remove from {} listener's queue", name, listenerKey);
} finally {
-
// We're exiting, gracefully or not - either way make sure we always remove
// ourselves from the cache.
-
- listenerCache.remove( listenerKey );
+ listenerCache.remove(listenerKey, this);
}
}
- private void notifyListener( N notification ) {
-
- if( notification == null ) {
+ private void notifyListener(final N notification) {
+ if (notification == null) {
return;
}
+ LOG.debug("{}: Invoking listener {} with notification: {}", name, listenerKey, notification);
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;
+ listenerInvoker.invokeListener(listenerKey.getListener(), notification);
+ } catch (Exception 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), e);
}
}
}
Code Review / yangtools.git / blobdiff