| /* |
| * Copyright 2016-present Open Networking Laboratory |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.onosproject.store.service; |
| |
| import java.util.Map; |
| import java.util.concurrent.CompletableFuture; |
| import java.util.function.Consumer; |
| |
| import org.onosproject.cluster.Leadership; |
| import org.onosproject.cluster.NodeId; |
| import org.onosproject.event.Change; |
| import org.onosproject.store.primitives.DefaultLeaderElector; |
| |
| /** |
| * Distributed mutual exclusion primitive. |
| * <p> |
| * {@code AsyncLeaderElector} facilitates mutually exclusive access to a shared resource by various cluster members. |
| * Each resource is identified by a unique topic name and members register their desire to access the resource by |
| * calling the {@link AsyncLeaderElector#run run} method. Access is grated on a FIFO basis. An instance can |
| * unregister itself from the leadership election by calling {@link AsyncLeaderElector#withdraw withdraw} method. |
| * If an instance currently holding the resource dies then the next instance waiting to be leader (in FIFO order) |
| * will be automatically granted access to the resource. |
| * <p> |
| * One can register listeners to be notified when a leadership change occurs. The Listeners are notified via a |
| * {@link Leadership} {@link Change change} subject. |
| * <p> |
| * Additionally, {@code AsyncLeaderElector} provides methods to query the current state of leadership for topics. |
| * <p> |
| * All methods of this interface return a {@link CompletableFuture future} immediately after a successful invocation. |
| * The operation itself is executed asynchronous and the returned future will be |
| * {@link CompletableFuture#complete completed} when the operation finishes. |
| */ |
| public interface AsyncLeaderElector extends DistributedPrimitive { |
| |
| @Override |
| default DistributedPrimitive.Type primitiveType() { |
| return DistributedPrimitive.Type.LEADER_ELECTOR; |
| } |
| |
| /** |
| * Attempts to become leader for a topic. |
| * @param topic leadership topic |
| * @param nodeId instance identifier of the node |
| * @return CompletableFuture that is completed with the current Leadership state of the topic |
| */ |
| CompletableFuture<Leadership> run(String topic, NodeId nodeId); |
| |
| /** |
| * Withdraws from leadership race for a topic. |
| * @param topic leadership topic |
| * @return CompletableFuture that is completed when the withdraw is done |
| */ |
| CompletableFuture<Void> withdraw(String topic); |
| |
| /** |
| * Attempts to promote a node to leadership displacing the current leader. |
| * @param topic leadership topic |
| * @param nodeId instance identifier of the new leader |
| * @return CompletableFuture that is completed with a boolean when the operation is done. Boolean is true if |
| * leadership transfer was successfully executed; false if it failed. This operation can fail (i.e. return false) |
| * if the node to be made new leader is not registering to run for election for the topic. |
| */ |
| CompletableFuture<Boolean> anoint(String topic, NodeId nodeId); |
| |
| /** |
| * Attempts to evict a node from all leadership elections it is registered for. |
| * <p> |
| * If the node is the current leader for a topic, this call will promote the next top candidate |
| * (if one exists) to leadership. |
| * |
| * @param nodeId node instance identifier |
| * @return CompletableFuture that is completed when the operation is done. |
| */ |
| CompletableFuture<Void> evict(NodeId nodeId); |
| |
| /** |
| * Attempts to promote a node to top of candidate list without displacing the current leader. |
| * |
| * @param topic leadership topic |
| * @param nodeId instance identifier of the new top candidate |
| * @return CompletableFuture that is completed with a boolean when the operation is done. Boolean is true if |
| * node is now the top candidate. This operation can fail (i.e. return false) if the node |
| * is not registered to run for election for the topic. |
| */ |
| CompletableFuture<Boolean> promote(String topic, NodeId nodeId); |
| |
| /** |
| * Returns the {@link Leadership} for the specified topic. |
| * @param topic leadership topic |
| * @return CompletableFuture that is completed with the current Leadership state of the topic |
| */ |
| CompletableFuture<Leadership> getLeadership(String topic); |
| |
| /** |
| * Returns the current {@link Leadership}s for all topics. |
| * @return CompletableFuture that is completed with the topic to Leadership mapping |
| */ |
| CompletableFuture<Map<String, Leadership>> getLeaderships(); |
| |
| /** |
| * Registers a listener to be notified of Leadership changes for all topics. |
| * @param consumer listener to notify |
| * @return CompletableFuture that is completed when the operation completes |
| */ |
| CompletableFuture<Void> addChangeListener(Consumer<Change<Leadership>> consumer); |
| |
| /** |
| * Unregisters a previously registered change notification listener. |
| * <p> |
| * If the specified listener was not previously registered, this operation will be a noop. |
| * @param consumer listener to remove |
| * @return CompletableFuture that is completed when the operation completes |
| */ |
| CompletableFuture<Void> removeChangeListener(Consumer<Change<Leadership>> consumer); |
| |
| /** |
| * Returns a new {@link LeaderElector} that is backed by this instance. |
| * |
| * @param timeoutMillis timeout duration for the returned LeaderElector operations |
| * @return new {@code LeaderElector} instance |
| */ |
| default LeaderElector asLeaderElector(long timeoutMillis) { |
| return new DefaultLeaderElector(this, timeoutMillis); |
| } |
| |
| /** |
| * Returns a new {@link LeaderElector} that is backed by this instance and with a default operation timeout. |
| * |
| * @return new {@code LeaderElector} instance |
| */ |
| default LeaderElector asLeaderElector() { |
| return asLeaderElector(DistributedPrimitive.DEFAULT_OPERTATION_TIMEOUT_MILLIS); |
| } |
| } |