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.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.api.ClusterSingletonService;
16 import org.opendaylight.mdsal.singleton.api.ServiceGroupIdentifier;
17 import org.opendaylight.yangtools.concepts.Identifiable;
20 * {@link ServiceGroup} maintains a group of {@link ClusterSingletonService} instances.
21 * All EntityOwnershipChange notifications have to applied to all registered services at the same time in the same
22 * manner. All registered services have only one instantiated service instance in a cluster at one time on same
23 * Cluster Node. This is realized via a double candidate approach where a service group instance maintains a candidate
24 * registration for ownership of the service entity in the cluster and also a registration that acts as a guard to
25 * ensure a service group instance has fully closed prior to relinquishing service ownership. To achieve ownership
26 * of the service group, a service group candidate must hold ownership of both these entities.
28 abstract sealed class ServiceGroup implements Identifiable<ServiceGroupIdentifier>
29 permits ActiveServiceGroup, PlaceholderServiceGroup {
31 * This method must be called once on startup to initialize this group and register the relevant group entity
32 * candidate. It means create relevant Group Entity Candidate Registration.
34 abstract void initialize() throws CandidateAlreadyRegisteredException;
37 * This method registers a service instance for this service group. If the local node has ownership of the service
38 * group, the {@link ClusterSingletonService#instantiateServiceInstance()} method is called. Otherwise, the method
39 * is called once the local node gains ownership.
41 * @param service instance
43 abstract void registerService(ServiceRegistration reg);
46 * Method provides possibility to restart some service from group without change leadership for whole group.
47 * {@link ServiceRegistration#removeRegistration()} implementation has to call this service.
50 * Candidates are signed for group, so unregistration for group with one service has to trigger new election only
51 * otherwise we can see same behavior as on server without clustering.
53 * @param service instance
54 * @return Future which completes when this instance is shutdown if this was the last registration, null otherwise
56 abstract @Nullable ListenableFuture<?> unregisterService(ServiceRegistration reg);
59 * Method implementation has to apply ownershipChange for all registered services.
61 * @param entity the entity whose ownership status changed
62 * @param change the change the entity underwent
63 * @param inJeopardy {@code true} if ownership is in jeopardy and the reported change may be inaccurate
65 abstract void ownershipChanged(DOMEntity entity, EntityOwnershipStateChange change, boolean inJeopardy);
68 * Closes this service group. All registered service providers are also closed. Please be careful
69 * and use this method without active EOS listener only.
71 * @return {@link ListenableFuture} in list for all Future from closing {@link ClusterSingletonService}
73 abstract ListenableFuture<?> closeClusterSingletonGroup();