com.netflix.genie.web.spring.actuators.LeaderElectionActuator Maven / Gradle / Ivy

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/*
 *
 *  Copyright 2020 Netflix, Inc.
 *
 *     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 com.netflix.genie.web.spring.actuators;

import com.google.common.collect.ImmutableMap;
import com.netflix.genie.web.services.ClusterLeaderService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
import org.springframework.boot.actuate.endpoint.annotation.WriteOperation;

import java.util.Map;


/**
 * An actuator endpoint that exposes leadership status and allows stop/start/restart of the leader election service.
 * Useful when a specific set of nodes should be given priority to win the leader election (e.g., because they are
 * running newer code).
 *
 * @author mprimi
 * @since 4.0.0
 */
@Endpoint(id = "leaderElection")
@Slf4j
public class LeaderElectionActuator {

    private static final String RUNNING = "running";
    private static final String LEADER = "leader";
    private final ClusterLeaderService clusterLeaderService;

    /**
     * Constructor.
     *
     * @param clusterLeaderService the cluster leader service
     */
    public LeaderElectionActuator(final ClusterLeaderService clusterLeaderService) {
        this.clusterLeaderService = clusterLeaderService;
    }

    /**
     * Provides the current leader service status: whether the leader service is running and whether the node is leader.
     *
     * @return a map of attributes
     */
    @ReadOperation
    public Map getStatus() {
        return ImmutableMap.builder()
            .put(RUNNING, this.clusterLeaderService.isRunning())
            .put(LEADER, this.clusterLeaderService.isLeader())
            .build();
    }

    /**
     * Forces the node to leave the leader election, then re-join it.
     *
     * @param action the action to perform
     */
    @WriteOperation
    public void doAction(final Action action) {
        switch (action) {
            case START:
                log.info("Starting leader election service");
                this.clusterLeaderService.start();
                break;
            case STOP:
                log.info("Stopping leader election service");
                this.clusterLeaderService.stop();
                break;
            case RESTART:
                log.info("Restarting leader election service");
                this.clusterLeaderService.stop();
                this.clusterLeaderService.start();
                break;
            default:
                log.error("Unknown action: " + action);
                throw new UnsupportedOperationException("Unknown action: " + action.name());
        }
    }

    /**
     * Operations that this actuator can perform on the leader service.
     */
    public enum Action {
        /**
         * Stop the leader election service.
         */
        STOP,
        /**
         * Start the leader election service.
         */
        START,
        /**
         * Stop then start the leader election service.
         */
        RESTART,

        /**
         * NOOP action for the purpose of testing unknown actions.
         */
        TEST,
    }
}