RocketMQ源码 Broker-BrokerFastFailure 快速失败请求组件源码分析

前言

BrokerFastFailure 快速失败处理组件，主要负责，在系统激活broker快速失败能力时，以后台定时调度任务方式进行过期任务清理。主要对以下几类任务进行处理：

1. 消息存储组件中的请求。如果消息存储组件中的OSPageCacheBusy（系统页缓存繁忙）为true，则对它的请求循环进行快速失败处理。
2. 清理发送线程池队列中的过期请求。
3. 清理拉取线程池队列中的过期请求。
4. 清理心跳线程池队列中的过期请求。
5. 清理事务线程池队列中的过期请求。

源码版本：4.9.3

源码分析

源码比较短，仅仅100多行，源码 + 注释 如下：

// broker快速失败组件
public class BrokerFastFailure {
    private static final InternalLogger log = InternalLoggerFactory.getLogger(LoggerName.BROKER_LOGGER_NAME);
    // broker快速失败调度线程池
    private final ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(new ThreadFactoryImpl(
        "BrokerFastFailureScheduledThread"));
    private final BrokerController brokerController;

    public BrokerFastFailure(final BrokerController brokerController) {
        this.brokerController = brokerController;
    }

    // 对线程进行转换
    public static RequestTask castRunnable(final Runnable runnable) {
        try {
            if (runnable instanceof FutureTaskExt) {
                FutureTaskExt object = (FutureTaskExt) runnable;
                return (RequestTask) object.getRunnable();
            }
        } catch (Throwable e) {
            log.error(String.format("castRunnable exception, %s", runnable.getClass().getName()), e);
        }

        return null;
    }

    public void start() {
        // 注册定时调度任务
        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                // 如果激活快速失败功能
                if (brokerController.getBrokerConfig().isBrokerFastFailureEnable()) {
                    // 清理过期请求
                    cleanExpiredRequest();
                }
            }
        }, 1000, 10, TimeUnit.MILLISECONDS);
    }

    private void cleanExpiredRequest() {
        // 如果消息存储组件中的OSPageCacheBusy（系统页缓存繁忙）为true，则进行快速失败处理
        while (this.brokerController.getMessageStore().isOSPageCacheBusy()) {
            try {

                // 取出发送线程池队列中的线程，并进行快速失败处理
                if (!this.brokerController.getSendThreadPoolQueue().isEmpty()) {
                    final Runnable runnable = this.brokerController.getSendThreadPoolQueue().poll(0, TimeUnit.SECONDS);
                    if (null == runnable) {
                        break;
                    }

                    final RequestTask rt = castRunnable(runnable);
                    rt.returnResponse(RemotingSysResponseCode.SYSTEM_BUSY, String.format("[PCBUSY_CLEAN_QUEUE]broker busy, start flow control for a while, period in queue: %sms, size of queue: %d", System.currentTimeMillis() - rt.getCreateTimestamp(), this.brokerController.getSendThreadPoolQueue().size()));
                } else {
                    break;
                }
            } catch (Throwable ignored) {
            }
        }
        // 清理发送线程池队列中的过期请求
        cleanExpiredRequestInQueue(this.brokerController.getSendThreadPoolQueue(),
            this.brokerController.getBrokerConfig().getWaitTimeMillsInSendQueue());
        // 清理拉取线程池队列中的过期请求
        cleanExpiredRequestInQueue(this.brokerController.getPullThreadPoolQueue(),
            this.brokerController.getBrokerConfig().getWaitTimeMillsInPullQueue());
        // 清理心跳线程池队列中的过期请求
        cleanExpiredRequestInQueue(this.brokerController.getHeartbeatThreadPoolQueue(),
            this.brokerController.getBrokerConfig().getWaitTimeMillsInHeartbeatQueue());
        // 清理事务线程池队列中的过期请求
        cleanExpiredRequestInQueue(this.brokerController.getEndTransactionThreadPoolQueue(), this
            .brokerController.getBrokerConfig().getWaitTimeMillsInTransactionQueue());
    }

    void cleanExpiredRequestInQueue(final BlockingQueue blockingQueue, final long maxWaitTimeMillsInQueue) {
        while (true) {
            try {
                if (!blockingQueue.isEmpty()) {
                    // 死循环访问队列，将队列头部所有过期请求清理掉，直到处理到一个没有过期的请求
                    final Runnable runnable = blockingQueue.peek();
                    if (null == runnable) {
                        break;
                    }
                    final RequestTask rt = castRunnable(runnable);
                    if (rt == null || rt.isStopRun()) {
                        break;
                    }

                    // 计算当前请求是否过期
                    final long behind = System.currentTimeMillis() - rt.getCreateTimestamp();
                    if (behind >= maxWaitTimeMillsInQueue) {
                        // 过期后移除当前请求
                        if (blockingQueue.remove(runnable)) {
                            // 设置当前请求为停止状态
                            rt.setStopRun(true);
                            // 返回当前请求响应
                            rt.returnResponse(RemotingSysResponseCode.SYSTEM_BUSY, String.format("[TIMEOUT_CLEAN_QUEUE]broker busy, start flow control for a while, period in queue: %sms, size of queue: %d", behind, blockingQueue.size()));
                        }
                    } else {
                        break;
                    }
                } else {
                    break;
                }
            } catch (Throwable ignored) {
            }
        }
    }

    public void shutdown() {
        this.scheduledExecutorService.shutdown();
    }