Start And Stop Heartbeat In Shell

Programmatically configuring a scheduler in Spring makes it feasible to switch on/off of a scheduling tasks in shell.

This entry shows a scenario where I need to start heartbeat generator and stop it; the benefit of doing this is that I could dynamically control event generation, publication and subscription.

The application.properties has a parameter for “infra.ebs.heartbeat.cron” for 1 second interval; if not found, it uses 1 minute interval by default.

Shell command “heartbeat –start” will start scheduler to make HeartBeatGenerator to generate and publish HeartBeatEvent.

Shell command “heartbeat” by default will disable the publishing.

package com.hedge.panda.shell.play;

import java.util.TimerTask;
import java.util.concurrent.ScheduledFuture;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.shell.standard.ShellComponent;
import org.springframework.shell.standard.ShellMethod;

import com.hedge.panda.infra.ebs.HeartBeatGenerator;

/**
 * @author wofon
 *
 */
@ShellComponent
public class EventCommands {
	@Value("${infra.ebs.heartbeat.cron:* */1 * * * *}")
	private String cron;

	public EventCommands() {
	}

	@Autowired TaskScheduler scheduler;
	private ScheduledFuture<?> task = null;
	@Autowired HeartBeatGenerator generator;
	@ShellMethod("heart beat start to generate events at 1 sec interval.")
	public String heartbeat(boolean start) {
		if(start) {
			task = this.scheduler.schedule(
					new TimerTask() {
						@Override
						public void run() {
							generator.generateEvent();
						}
					},
					new CronTrigger(cron)
					);
			return "heartbeat starts ticking...";
		}else {
			if(task!=null) {
				task.cancel(true);
			}
			return "heartbeat canceled.";
		}
	}
}