@RefreshScope 停止@Scheduled 任务

Question

我有一个监控应用程序，其中正在运行固定速率任务。这是拉入用 Consul 配置的配置参数。我想引入更新的配置，所以我添加了@RefreshScope。但是，一旦我更新 Consul 上的配置值，fixedRate 任务就会停止运行。

@Service
@RefreshScope
public class MonitorService {

    @Autowired
    private AppConfig appConfig;

    @PostConstruct
    public void postConstRun() {
        System.out.println(appConfig.getMonitorConfig());
    }

    @Scheduled(fixedRate = 1000)
    public void scheduledMonitorScan() {
        System.out.println("MonitorConfig:" + appConfig.getMonitorConfig());
    }
}

AppConfig 类只有一个 String 参数：

@Configuration
@Getter
@Setter
public class AppConfig {

    @Value("${monitor-config:default value}")
    private String monitorConfig;
}

一旦我更新领事中的值，计划任务就会停止运行（在 sheduledMonitorScan 方法中显示）并停止显示。

Answer 1

我成功地获取并覆盖了来自领事配置服务器的值RefreshScopeRefreshedEvent

import java.text.SimpleDateFormat;
import java.util.Date;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.cloud.context.scope.refresh.RefreshScopeRefreshedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
@RefreshScope
public class AlertSchedulerCron implements ApplicationListener<RefreshScopeRefreshedEvent> {

    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    @Value("${pollingtime}")
    private String pollingtime;
    
    /*
     * @Value("${interval}") private String interval;
     */
    @Scheduled(cron = "${pollingtime}")
    //@Scheduled(fixedRateString = "${interval}" )
    public void task() {

        System.out.println(pollingtime);
        System.out.println("Scheduler (cron expression) task with duration : " + sdf.format(new Date()));
    }

    @Override
    public void onApplicationEvent(RefreshScopeRefreshedEvent event) {
        // TODO Auto-generated method stub
        
    }

    
}

Answer 2

以下是我们解决此问题的方法。

/**
 * Listener of Spring's lifecycle to revive Scheduler beans, when spring's
 * scope is refreshed.
 * <p>
 * Spring is able to restart beans, when we change their properties. Such a
 * beans marked with RefreshScope annotation. To make it work, spring creates
 * <b>lazy</b> proxies and push them instead of real object. The issue with
 * scope refresh is that right after refresh in order for such a lazy proxy
 * to be actually instantiated again someone has to call for any method of it.
 * <p>
 * It creates a tricky case with Schedulers, because there is no bean, which
 * directly call anything on any Scheduler. Scheduler lifecycle is to start
 * few threads upon instantiation and schedule tasks. No other bean needs
 * anything from them.
 * <p>
 * To overcome this, we had to create artificial method on Schedulers and call
 * them, when there is a scope refresh event. This actually instantiates.
 */
@RequiredArgsConstructor
public class RefreshScopeListener implements ApplicationListener<RefreshScopeRefreshedEvent> {
    private final List<RefreshScheduler> refreshSchedulers;

    @Override
    public void onApplicationEvent(RefreshScopeRefreshedEvent event) {
        refreshSchedulers.forEach(RefreshScheduler::materializeAfterRefresh);
    }
}

因此，我们定义了一个接口，它不执行任何具体操作，但允许我们调用刷新的作业。

public interface RefreshScheduler {
    /**
     * Used after refresh context for scheduler bean initialization
     */
    default void materializeAfterRefresh() {
    }
}

这里是实际的作业，其参数from.properties可以刷新。

public class AJob implements RefreshScheduler {
    @Scheduled(cron = "${from.properties}")
    public void aTask() {
        // do something useful
    }
}

更新：当然AJob bean必须在@Configuration中用@RefreshScope标记

@Configuration
@EnableScheduling
public class SchedulingConfiguration {
    @Bean
    @RefreshScope
    public AJob aJob() {
        return new AJob();
    }
}

Answer 3

我已经通过实现 SchedulingConfigurer 接口来解决这种情况。在这里，我从外部属性文件动态更新“scheduler.interval”属性，即使在执行器刷新之后，调度程序也能正常工作，因为我不再使用@RefreshScope。希望这对您的情况也有帮助。

public class MySchedulerImpl implements SchedulingConfigurer {

    @Autowired
    private Environment env;

    @Bean(destroyMethod = "shutdown")
    public Executor taskExecutor() {
        return Executors.newScheduledThreadPool(10);
    }

    @Override
    public void configureTasks(final ScheduledTaskRegistrar taskRegistrar) {
        taskRegistrar.setScheduler(this.taskExecutor());
        taskRegistrar.addTriggerTask(() -> {
            //put your code here that to be scheduled
        }, triggerContext -> {
            final Calendar nextExecutionTime = new GregorianCalendar();
            final Date lastActualExecutionTime = triggerContext.lastActualExecutionTime();

            if (lastActualExecutionTime == null) {
                nextExecutionTime.setTime(new Date());
            } else {
                nextExecutionTime.setTime(lastActualExecutionTime);
                nextExecutionTime.add(Calendar.MILLISECOND, env.getProperty("scheduler.interval", Integer.class));
            }
            return nextExecutionTime.getTime();
        });
    }
}