/*
* Copyright (c) 2014 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.md.sal.dom.api;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import org.opendaylight.controller.sal.core.api.BrokerService;
/**
* A {@link DOMService} which allows its user to send {@link DOMNotification}s. It
* provides two styles of initiating the notification delivery, similar to
* {@link java.util.concurrent.BlockingQueue}:
* - a put-style method which waits until the implementation can accept the notification
* for delivery, and
* - an offer-style method, which attempts to enqueue the notification, but allows
* the caller to specify that it should never wait, or put an upper bound on how
* long it is going to wait.
*/
public interface DOMNotificationPublishService extends DOMService, BrokerService {
/**
* Well-known value indicating that the implementation is currently not
* able to accept a notification.
*/
ListenableFuture<Object> REJECTED = Futures.immediateFailedFuture(new DOMNotificationRejectedException("Unacceptable blocking conditions encountered"));
/**
* Publish a notification. The result of this method is a {@link ListenableFuture}
* which will complete once the notification has been delivered to all immediate
* registrants. The type of the object resulting from the future is not defined
* and implementations may use it to convey additional information related to the
* publishing process.
*
* Abstract subclasses can refine the return type as returning a promise of a
* more specific type, e.g.:
*
* {@code
* public interface DeliveryStatus { int getListenerCount(); }
* ListenableFuture<? extends DeliveryStatus> putNotification(DOMNotification notification);
* }
*
* Once the Future succeeds, the resulting object can be queried for traits using
* instanceof, e.g:
*
* {@code
* // Can block when (for example) the implemention's ThreadPool queue is full
* Object o = service.putNotification(notif).get();
* if (o instanceof DeliveryStatus) {
* DeliveryStatus ds = (DeliveryStatus)o;
* LOG.debug("Notification was received by {} listeners", ds.getListenerCount(););
* }
* }
*
* In case an implementation is running out of resources, it can block the calling
* thread until enough resources become available to accept the notification for
* processing, or it is interrupted.
*
* Caution: completion here means that the implementation has completed processing
* of the notification. This does not mean that all existing registrants
* have seen the notification. Most importantly, the delivery process at
* other cluster nodes may have not begun yet.
*
* @param notification Notification to be published.
* @return A listenable future which will report completion when the service
* has finished propagating the notification to its immediate registrants.
* @throws InterruptedException if interrupted while waiting
* @throws NullPointerException if notification is null.
*/
@Nonnull ListenableFuture<?> putNotification(@Nonnull DOMNotification notification) throws InterruptedException;
/**
* Attempt to publish a notification. The result of this method is a {@link ListenableFuture}
* which will complete once the notification has been delivered to all immediate
* registrants. The type of the object resulting from the future is not defined
* and implementations may use it to convey additional information related to the
* publishing process. Unlike {@link #putNotification(DOMNotification)}, this method
* is guaranteed not to block if the underlying implementation encounters contention.
*
* @param notification Notification to be published.
* @return A listenable future which will report completion when the service
* has finished propagating the notification to its immediate registrants,
* or {@link #REJECTED} if resource constraints prevent
* the implementation from accepting the notification for delivery.
* @throws NullPointerException if notification is null.
*/
@Nonnull ListenableFuture<?> offerNotification(@Nonnull DOMNotification notification);
/**
* Attempt to publish a notification. The result of this method is a {@link ListenableFuture}
* which will complete once the notification has been delivered to all immediate
* registrants. The type of the object resulting from the future is not defined
* and implementations may use it to convey additional information related to the
* publishing process. Unlike {@link #putNotification(DOMNotification)}, this method
* is guaranteed to block more than the specified timeout.
*
* @param notification Notification to be published.
* @param timeout how long to wait before giving up, in units of unit
* @param unit a TimeUnit determining how to interpret the timeout parameter
* @return A listenable future which will report completion when the service
* has finished propagating the notification to its immediate registrants,
* or {@link #REJECTED} if resource constraints prevent
* the implementation from accepting the notification for delivery.
* @throws InterruptedException if interrupted while waiting
* @throws NullPointerException if notification or unit is null.
* @throws IllegalArgumentException if timeout is negative.
*/
@Nonnull ListenableFuture<?> offerNotification(@Nonnull DOMNotification notification,
@Nonnegative long timeout, @Nonnull TimeUnit unit) throws InterruptedException;
}