Madan Jampani | 47b80ba | 2016-01-31 23:05:55 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2016 Open Networking Laboratory |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.onosproject.store.service; |
| 17 | |
| 18 | import java.util.Map; |
| 19 | import java.util.concurrent.CompletableFuture; |
| 20 | import java.util.function.Consumer; |
| 21 | |
| 22 | import org.onosproject.cluster.Leadership; |
| 23 | import org.onosproject.cluster.NodeId; |
| 24 | import org.onosproject.event.Change; |
| 25 | |
| 26 | /** |
| 27 | * Distributed mutual exclusion primitive. |
| 28 | * <p> |
| 29 | * {@code AsyncLeaderElector} facilitates mutually exclusive access to a shared resource by various cluster members. |
| 30 | * Each resource is identified by a unique topic name and members register their desire to access the resource by |
| 31 | * calling the {@link AsyncLeaderElector#run run} method. Access is grated on a FIFO basis. An instance can |
| 32 | * unregister itself from the leadership election by calling {@link AsyncLeaderElector#withdraw withdraw} method. |
| 33 | * If an instance currently holding the resource dies then the next instance waiting to be leader (in FIFO order) |
| 34 | * will be automatically granted access to the resource. |
| 35 | * <p> |
| 36 | * One can register listeners to be notified when a leadership change occurs. The Listeners are notified via a |
| 37 | * {@link Leadership} {@link Change change} subject. |
| 38 | * <p> |
| 39 | * Additionally, {@code AsyncLeaderElector} provides methods to query the current state of leadership for topics. |
| 40 | * <p> |
| 41 | * All methods of this interface return a {@link CompletableFuture future} immediately after a successful invocation. |
| 42 | * The operation itself is executed asynchronous and the returned future will be |
| 43 | * {@link CompletableFuture#complete completed} when the operation finishes. |
| 44 | */ |
| 45 | public interface AsyncLeaderElector extends DistributedPrimitive { |
| 46 | |
| 47 | @Override |
| 48 | default DistributedPrimitive.Type type() { |
| 49 | return DistributedPrimitive.Type.LEADER_ELECTOR; |
| 50 | } |
| 51 | |
| 52 | /** |
| 53 | * Attempts to become leader for a topic. |
| 54 | * @param topic leadership topic |
| 55 | * @param nodeId instance identifier of the node |
| 56 | * @return CompletableFuture that is completed with the current Leadership state of the topic |
| 57 | */ |
| 58 | CompletableFuture<Leadership> run(String topic, NodeId nodeId); |
| 59 | |
| 60 | /** |
| 61 | * Withdraws from leadership race for a topic. |
| 62 | * @param topic leadership topic |
| 63 | * @return CompletableFuture that is completed when the withdraw is done |
| 64 | */ |
| 65 | CompletableFuture<Void> withdraw(String topic); |
| 66 | |
| 67 | /** |
| 68 | * Attempts to promote a node to leadership displacing the current leader. |
| 69 | * @param topic leadership topic |
| 70 | * @param nodeId instance identifier of the new leader |
| 71 | * @return CompletableFuture that is completed with a boolean when the operation is done. Boolean is true if |
| 72 | * leadership transfer was successfully executed; false if it failed. This operation can fail (i.e. return false) |
| 73 | * if the node to be made new leader is not registering to run for election for the topic. |
| 74 | */ |
| 75 | CompletableFuture<Boolean> anoint(String topic, NodeId nodeId); |
| 76 | |
| 77 | /** |
| 78 | * Returns the {@link Leadership} for the specified topic. |
| 79 | * @param topic leadership topic |
| 80 | * @return CompletableFuture that is completed with the current Leadership state of the topic |
| 81 | */ |
| 82 | CompletableFuture<Leadership> getLeadership(String topic); |
| 83 | |
| 84 | /** |
| 85 | * Returns the current {@link Leadership}s for all topics. |
| 86 | * @return CompletableFuture that is completed with the topic to Leadership mapping |
| 87 | */ |
| 88 | CompletableFuture<Map<String, Leadership>> getLeaderships(); |
| 89 | |
| 90 | /** |
| 91 | * Registers a listener to be notified of Leadership changes for all topics. |
| 92 | * @param consumer listener to notify |
| 93 | * @return CompletableFuture that is completed when the operation completes |
| 94 | */ |
| 95 | CompletableFuture<Void> addChangeListener(Consumer<Change<Leadership>> consumer); |
| 96 | |
| 97 | /** |
| 98 | * Unregisters a previously registered change notification listener. |
| 99 | * <p> |
| 100 | * If the specified listener was not previously registered, this operation will be a noop. |
| 101 | * @param consumer listener to remove |
| 102 | * @return CompletableFuture that is completed when the operation completes |
| 103 | */ |
| 104 | CompletableFuture<Void> removeChangeListener(Consumer<Change<Leadership>> consumer); |
| 105 | } |