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.GenericEntity;
14 import org.opendaylight.mdsal.eos.common.api.GenericEntityOwnershipChange;
15 import org.opendaylight.mdsal.singleton.common.api.ClusterSingletonService;
16 import org.opendaylight.mdsal.singleton.common.api.ClusterSingletonServiceRegistration;
17 import org.opendaylight.yangtools.concepts.Identifiable;
18 import org.opendaylight.yangtools.concepts.Path;
21 * {@link ClusterSingletonServiceGroup} maintains a group of {@link ClusterSingletonService} instances.
22 * All EntityOwnershipChange notifications have to applied to all registered services at the same time in the same
23 * manner. All registered services have only one instantiated service instance in a cluster at one time on same
24 * Cluster Node. This is realized via a double candidate approach where a service group instance maintains a candidate
25 * registration for ownership of the service entity in the cluster and also a registration that acts as a guard to
26 * ensure a service group instance has fully closed prior to relinquishing service ownership. To achieve ownership
27 * of the service group, a service group candidate must hold ownership of both these entities.
29 * @param <P> the instance identifier path type
30 * @param <E> the GenericEntity type
31 * @param <C> the GenericEntityOwnershipChange type
33 abstract class ClusterSingletonServiceGroup<P extends Path<P>, E extends GenericEntity<P>,
34 C extends GenericEntityOwnershipChange<P, E>> implements Identifiable<String> {
37 * This method must be called once on startup to initialize this group and
38 * register the relevant group entity candidate. It means create relevant
39 * Group Entity Candidate Registration.
41 abstract void initialize() throws CandidateAlreadyRegisteredException;
44 * This method registers a service instance for this service group. If the local node has
45 * ownership of the service group, the {@link ClusterSingletonService#instantiateServiceInstance()}
46 * method is called. Otherwise, the method is called once the local node gains ownership.
48 * @param service instance
50 abstract void registerService(ClusterSingletonServiceRegistration reg);
53 * Method provides possibility to restart some service from group without change
54 * leadership for whole group. {@link ClusterSingletonServiceRegistration#close()}
55 * implementation has to call this service.
56 * Candidates are signed for group, so unregistration for group with one service
57 * has to trigger new election only otherwise we can see same behavior as on server
60 * @param service instance
61 * @return Future which completes when this instance is shutdown if this was the last registration, null otherwise
63 abstract @Nullable ListenableFuture<?> unregisterService(ClusterSingletonServiceRegistration reg);
66 * Method implementation has to apply ownershipChange for all registered services.
68 * @param ownershipChange change role for ClusterSingletonServiceGroup
70 abstract void ownershipChanged(C ownershipChange);
73 * Closes this service group. All registered service providers are also closed. Please be careful
74 * and use this method without active EOS listener only.
76 * @return {@link ListenableFuture} in list for all Future from closing {@link ClusterSingletonService}
78 abstract ListenableFuture<?> closeClusterSingletonGroup();