@RefreshScope stops @Scheduled task

问题

I have a monitoring app wherein I am running a fixedRate task. This is pulling in a config parameter configured with Consul. I want to pull in updated configuration, so I added @RefreshScope. But as soon as I update the config value on Consul, the fixedRate task stops running.

@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 class just has a single String parameter:

@Configuration
@Getter
@Setter
public class AppConfig {

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

As soon as I update the value in consul, the scheduled task just stops running (display in sheduledMonitorScan method) stop showing up.

回答1:

Here's how we've solved this issue.

/**
 * 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);
    }
}

So, we've defined an interface, which does nothing in particular, but allows us to call for a refreshed job.

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

And here is actual job, whose parameter from.properties can be refreshed.

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

UPDATED: Of course AJob bean must be marked with @RefreshScope in @Configuration

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

回答2:

My solution consists of listening to EnvironmentChangeEvent

@Configuration
public class SchedulingSpringConfig implements ApplicationListener<EnvironmentChangeEvent>, SchedulingConfigurer {

  private static final Logger LOGGER = LoggerFactory.getLogger(SchedulingSpringConfig.class);

  private final DemoProperties demoProperties;

  public SchedulingSpringConfig(DemoProperties demoProperties) {
    this.demoProperties = demoProperties;
  }

  @Override
  public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
    LOGGER.info("Configuring scheduled task with cron expression: {}", demoProperties.getCronExpression());
    taskRegistrar.addTriggerTask(triggerTask());
    taskRegistrar.setTaskScheduler(taskScheduler());
  }

  @Bean
  public TriggerTask triggerTask() {
    return new TriggerTask(this::work, cronTrigger());
  }

  private void work() {
    LOGGER.info("Doing work!");
  }

  @Bean
  @RefreshScope
  public CronTrigger cronTrigger() {
    return new CronTrigger(demoProperties.getCronExpression());
  }

  @Bean
  public ThreadPoolTaskScheduler taskScheduler() {
    return new ThreadPoolTaskScheduler();
  }

  @Override
  public void onApplicationEvent(EnvironmentChangeEvent event) {
    if (event.getKeys().contains("demo.config.cronExpression")) {
      ScheduledTasksRefresher scheduledTasksRefresher = new ScheduledTasksRefresher(triggerTask());
      scheduledTasksRefresher.afterPropertiesSet();
    }
  }
}

Then I use the ContextLifecycleScheduledTaskRegistrar to recreate the task.

public class ScheduledTasksRefresher extends ContextLifecycleScheduledTaskRegistrar {

  private final TriggerTask triggerTask;

  ScheduledTasksRefresher(TriggerTask triggerTask) {
    this.triggerTask = triggerTask;
  }

  @Override
  public void afterPropertiesSet() {
    super.destroy();
    super.addTriggerTask(triggerTask);
    super.afterSingletonsInstantiated();
  }
}

Properties definition:

@ConfigurationProperties(prefix = "demo.config", ignoreUnknownFields = false)
public class DemoProperties {

  private String cronExpression;

  public String getCronExpression() {
    return cronExpression;
  }

  public void setCronExpression(String cronExpression) {
    this.cronExpression = cronExpression;
  }
}

Main definition:

@SpringBootApplication
@EnableConfigurationProperties(DemoProperties.class)
@EnableScheduling
public class DemoApplication {

  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }
}

回答3:

I have done workaround for this kind of scenario by implementing SchedulingConfigurer interface. Here I am dynamically updating "scheduler.interval" property from external property file and scheduler is working fine even after actuator refresh as I am not using @RefreshScope anymore. Hope this might help you in your case also.

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();
        });
    }
}

来源：https://stackoverflow.com/questions/50440468/refreshscope-stops-scheduled-task