com.netflix.genie.web.tasks.leader.LocalLeader Maven / Gradle / Ivy
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/*
*
* Copyright 2016 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.tasks.leader;
import com.netflix.genie.web.events.GenieEventBus;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.integration.leader.event.OnGrantedEvent;
import org.springframework.integration.leader.event.OnRevokedEvent;
import javax.annotation.concurrent.ThreadSafe;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A class to control leadership activities when remote leadership isn't enabled and this node has been forcibly
* elected as the leader.
*
* @author tgianos
* @since 3.0.0
*/
@Slf4j
@ThreadSafe
public class LocalLeader {
private final GenieEventBus genieEventBus;
private final boolean isLeader;
private final AtomicBoolean isRunning;
/**
* Constructor.
*
* @param genieEventBus The spring application event publisher to use to invoke that this node is a leader
* @param isLeader Whether this node should be the leader or not. Should only be one in a cluster but not
* enforced by Genie at this time
*/
public LocalLeader(final GenieEventBus genieEventBus, final boolean isLeader) {
this.genieEventBus = genieEventBus;
this.isLeader = isLeader;
this.isRunning = new AtomicBoolean(false);
if (this.isLeader) {
log.info("Constructing LocalLeader. This node IS the leader.");
} else {
log.info("Constructing LocalLeader. This node IS NOT the leader.");
}
}
/**
* Auto-start once application is up and running.
*
* @param event The Spring Boot application ready event to startup on
*/
@EventListener
public void startLeadership(final ContextRefreshedEvent event) {
log.debug("Starting Leadership due to {}", event);
this.start();
}
/**
* Auto-stop once application is shutting down.
*
* @param event The application context closing event
*/
@EventListener
public void stopLeadership(final ContextClosedEvent event) {
log.debug("Stopping Leadership due to {}", event);
this.stop();
}
/**
* If configured to be leader and previously started, deactivate and send a leadership lost notification.
* NOOP if not running or if this node is not configured to be leader.
*/
public void stop() {
if (this.isRunning.compareAndSet(true, false) && this.isLeader) {
log.info("Stopping Leadership");
this.genieEventBus.publishSynchronousEvent(new OnRevokedEvent(this, null, "leader"));
}
}
/**
* If configured to be leader, activate and send a leadership acquired notification.
* NOOP if already running or if this node is not configured to be leader.
*/
public void start() {
if (this.isRunning.compareAndSet(false, true) && this.isLeader) {
log.debug("Starting Leadership");
this.genieEventBus.publishSynchronousEvent(new OnGrantedEvent(this, null, "leader"));
}
}
/**
* Whether this module is active.
*
* @return true if {@link LocalLeader#start()} was called.
*/
public boolean isRunning() {
return this.isRunning.get();
}
/**
* Whether local node is leader.
*
* @return true if this module is active and the node is configured to be leader
*/
public boolean isLeader() {
return this.isRunning() && this.isLeader;
}
}