Flume源码阅读记录（3）flume启动组件Application代码分析

最新推荐文章于 2021-01-04 16:48:03 发布

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最新推荐文章于 2021-01-04 16:48:03 发布 · 368 阅读

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本文深入探讨了Flume Application的源代码，重点关注start()和stop()方法中组件的启动与关闭顺序，LifecycleAware接口以及LifecycleSupervisor的角色。此外，还介绍了loadMonitoring()方法用于加载监控，以及PollingZooKeeperConfigurationProvider如何管理组件的启动停止，并通过supervise方法控制组件状态。

public class Application {

  private static final Logger logger = LoggerFactory
      .getLogger(Application.class);

  public static final String CONF_MONITOR_CLASS = "flume.monitoring.type";
  public static final String CONF_MONITOR_PREFIX = "flume.monitoring.";

  private final List<LifecycleAware> components;
  private final LifecycleSupervisor supervisor;
  private MaterializedConfiguration materializedConfiguration;
  private MonitorService monitorServer;
  //类持有的锁
  private final ReentrantLock lifecycleLock = new ReentrantLock();

  public Application() {
    this(new ArrayList<LifecycleAware>(0));
  }

  public Application(List<LifecycleAware> components) {
    this.components = components;
    supervisor = new LifecycleSupervisor();
  }


  //启动方法
  public void start() {
    lifecycleLock.lock();
    try {
      for (LifecycleAware component : components) {
        supervisor.supervise(component,
            new SupervisorPolicy.AlwaysRestartPolicy(), LifecycleState.START);
      }
    } finally {
      lifecycleLock.unlock();
    }
  }

  //更新配置文件时，执行以下方法。
  @Subscribe
  public void handleConfigurationEvent(MaterializedConfiguration conf) {
    try {
      lifecycleLock.lockInterruptibly();
      //先停止，再启动所有组件。
      stopAllComponents();
      startAllComponents(conf);
    } catch (InterruptedException e) {
      logger.info("Interrupted while trying to handle configuration event");
      return;
    } finally {
      // If interrupted while trying to lock, we don't own the lock, so must not attempt to unlock
      if (lifecycleLock.i