2 * Copyright (c) 2016 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.mdsal.singleton.dom.impl;
10 import com.google.common.util.concurrent.ListenableFuture;
11 import org.eclipse.jdt.annotation.Nullable;
12 import org.opendaylight.mdsal.eos.common.api.CandidateAlreadyRegisteredException;
13 import org.opendaylight.mdsal.eos.common.api.EntityOwnershipStateChange;
14 import org.opendaylight.mdsal.eos.dom.api.DOMEntity;
15 import org.opendaylight.mdsal.singleton.common.api.ClusterSingletonService;
16 import org.opendaylight.yangtools.concepts.Identifiable;
19 * {@link ClusterSingletonServiceGroup} maintains a group of {@link ClusterSingletonService} instances.
20 * All EntityOwnershipChange notifications have to applied to all registered services at the same time in the same
21 * manner. All registered services have only one instantiated service instance in a cluster at one time on same
22 * Cluster Node. This is realized via a double candidate approach where a service group instance maintains a candidate
23 * registration for ownership of the service entity in the cluster and also a registration that acts as a guard to
24 * ensure a service group instance has fully closed prior to relinquishing service ownership. To achieve ownership
25 * of the service group, a service group candidate must hold ownership of both these entities.
27 * @param <P> the instance identifier path type
28 * @param <E> the GenericEntity type
30 // FIXME: rename to ServiceGroup and seal
31 abstract class ClusterSingletonServiceGroup implements Identifiable<String> {
33 * This method must be called once on startup to initialize this group and register the relevant group entity
34 * candidate. It means create relevant Group Entity Candidate Registration.
36 abstract void initialize() throws CandidateAlreadyRegisteredException;
39 * This method registers a service instance for this service group. If the local node has ownership of the service
40 * group, the {@link ClusterSingletonService#instantiateServiceInstance()} method is called. Otherwise, the method
41 * is called once the local node gains ownership.
43 * @param service instance
45 abstract void registerService(ServiceRegistration reg);
48 * Method provides possibility to restart some service from group without change leadership for whole group.
49 * {@link ServiceRegistration#removeRegistration()} implementation has to call this service.
52 * Candidates are signed for group, so unregistration for group with one service has to trigger new election only
53 * otherwise we can see same behavior as on server without clustering.
55 * @param service instance
56 * @return Future which completes when this instance is shutdown if this was the last registration, null otherwise
58 abstract @Nullable ListenableFuture<?> unregisterService(ServiceRegistration reg);
61 * Method implementation has to apply ownershipChange for all registered services.
63 * @param entity the entity whose ownership status changed
64 * @param change the change the entity underwent
65 * @param inJeopardy {@code true} if ownership is in jeopardy and the reported change may be inaccurate
67 abstract void ownershipChanged(DOMEntity entity, EntityOwnershipStateChange change, boolean inJeopardy);
70 * Closes this service group. All registered service providers are also closed. Please be careful
71 * and use this method without active EOS listener only.
73 * @return {@link ListenableFuture} in list for all Future from closing {@link ClusterSingletonService}
75 abstract ListenableFuture<?> closeClusterSingletonGroup();