/*
* Copyright (c) 2015 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 java.util.Collection;
import javax.annotation.Nonnull;
import org.opendaylight.yangtools.concepts.ListenerRegistration;
/**
* A {@link DOMService} providing access to the conceptual data tree. Interactions
* with the data tree are split into data producers and consumers (listeners). Each
* of them operate on a set of subtrees, which need to be declared at instantiation time.
*
* Returned instances are not thread-safe and expected to be used by a single thread
* at a time. Furthermore, producers may not be accessed from consumer callbacks
* unless they were specified when the listener is registered.
*
* The service maintains a loop-free topology of producers and consumers. What this means
* is that a consumer is not allowed to access a producer, which affects any of the
* subtrees it is subscribed to. This restriction is in place to ensure the system does
* not go into a feedback loop, where it is impossible to block either a producer or
* a consumer without accumulating excess work in the backlog stemming from its previous
* activity.
*/
public interface DOMDataTreeService extends DOMDataTreeProducerFactory, DOMService {
/**
* Register a {@link DOMDataTreeListener} instance. Once registered, the listener
* will start receiving changes on the selected subtrees. If the listener cannot
* keep up with the rate of changes, and allowRxMerges is set to true, this service
* is free to merge the changes, so that a smaller number of them will be reported,
* possibly hiding some data transitions (like flaps).
*
* If the listener wants to write into any producer, that producer has to be mentioned
* in the call to this method. Those producers will be bound exclusively to the
* registration, so that accessing them outside of this listener's callback will trigger
* an error. Any producers mentioned must be idle, e.g. they may not have an open
* transaction at the time this method is invoked.
*
* Each listener instance can be registered at most once. Implementations of this
* interface have to guarantee that the listener's methods will not be invoked
* concurrently from multiple threads.
*
* @param listener {@link DOMDataTreeListener} that is being registered
* @param subtrees Conceptual subtree identifier of subtrees which should be monitored
* for changes. May not be null or empty.
* @param allowRxMerges True if the backend may perform ingress state compression.
* @param producers {@link DOMDataTreeProducer} instances to bind to the listener.
* @return A listener registration. Once closed, the listener will no longer be
* invoked and the producers will be unbound.
* @throws IllegalArgumentException if subtrees is empty or the listener is already bound
* @throws DOMDataTreeLoopException if the registration of the listener to the specified
* subtrees with specified producers would form a
* feedback loop
*/
@Nonnull <T extends DOMDataTreeListener> ListenerRegistration<T> registerListener(@Nonnull T listener,
@Nonnull Collection<DOMDataTreeIdentifier> subtrees, boolean allowRxMerges, @Nonnull Collection<DOMDataTreeProducer> producers) throws DOMDataTreeLoopException;
}