项目中一直在使用redis的subscribe功能，偶然会发生订阅断开的问题，一直无法定位，在此之下只能阅读源码定位问题
首先从spring.xml入手观察配置
RedisMessageListenerContainer类中有个Map专门放MessageListenerAdapter类型的监听，同时这个类也是整个监听的核心类，总共有1000行
RedisMessageListenerContainer
其实现了InitializingBean, DisposableBean, BeanNameAware, SmartLifecycle几个接口
InitializingBean：主要实现afterPropertiesSet方法，来定义spring设置完properties后进行的处理，在spring init这个bean时候会被调用
DisposableBean：实现destroy方法，在spring销毁bean时会调用
BeanNameAware：实现setBeanName方法来为bean进行取名，在RedisMessageListenerContainer中该name被用于内部线程的线程名
SmartLifecycle：spring的bean生命周期类，spring会调用start，stop等操作来完成RedisMessageListenerContainer类的启动
启动顺序
1.spring先完成对于bean属性的set，其中包含listener map的set操作
2.调用afterPropertiesSet方法
public void afterPropertiesSet() {
if (taskExecutor == null) {
manageExecutor = true;
taskExecutor = createDefaultTaskExecutor();
}
if (subscriptionExecutor == null) {
subscriptionExecutor = taskExecutor;
}
initialized = true;
}此方法构造了一个线程池来跑监听线程。
3.spring调用start方法来开启这个bean
public void start() {
if (!running) {
running = true;
// wait for the subscription to start before returning
// technically speaking we can only be notified right before the subscription starts
synchronized (monitor) {
lazyListen();
if (listening) {
try {
// wait up to 5 seconds for Subscription thread
monitor.wait(initWait);
} catch (InterruptedException e) {
// stop waiting
}
}
}
if (logger.isDebugEnabled()) {
logger.debug("Started RedisMessageListenerContainer");
}
}
}4.最重要的一步 lazyListen();方法的调用，下面是其源码
private void lazyListen() {
boolean debug = logger.isDebugEnabled();
boolean started = false;
if (isRunning()) {
if (!listening) {
synchronized (monitor) {
if (!listening) {
if (channelMapping.size() > 0 || patternMapping.size() > 0) {
subscriptionExecutor.execute(subscriptionTask);
listening = true;
started = true;
}
}
}
if (debug) {
if (started) {
logger.debug("Started listening for Redis messages");
} else {
logger.debug("Postpone listening for Redis messages until actual listeners are added");
}
}
}
}
}构造一个SubscriptionTask，并且提交给第二步afterPropertiesSet方法中创建的线程池来执行，SubscriptionTask是一个RedisMessageListenerContainer中的重要的内部类
SubscriptionTask
其run方法如下，在spring容器启动时刻，最终会在eventuallyPerformSubscription方法处阻塞，执行底层jedis的监听，调用的也是jedis的subscribe方法
public void run() {
synchronized (localMonitor) {
subscriptionTaskRunning = true;
}
try {
connection = connectionFactory.getConnection();
if (connection.isSubscribed()) {
throw new IllegalStateException("Retrieved connection is already subscribed; aborting listening");
}
boolean asyncConnection = ConnectionUtils.isAsync(connectionFactory);
// NB: async drivers' Xsubscribe calls block, so we notify the RDMLC before performing the actual subscription.
if (!asyncConnection) {
synchronized (monitor) {
monitor.notify();
}
}
SubscriptionPresentCondition subscriptionPresent = eventuallyPerformSubscription();
if (asyncConnection) {
SpinBarrier.waitFor(subscriptionPresent, getMaxSubscriptionRegistrationWaitingTime());
synchronized (monitor) {
monitor.notify();
}
}
} catch (Throwable t) {
handleSubscriptionException(t);
} finally {
// this block is executed once the subscription thread has ended, this may or may not mean
// the connection has been unsubscribed, depending on driver
synchronized (localMonitor) {
subscriptionTaskRunning = false;
localMonitor.notify();
}
}
}当有链接异常发生时，会进入catch代码块的handleSubscriptionException(t);方法，其实现如下
protected void handleSubscriptionException(Throwable ex) {
listening = false;
subscriptionTask.closeConnection();
if (ex instanceof RedisConnectionFailureException) {
if (isRunning()) {
logger.error("Connection failure occurred. Restarting subscription task after " + recoveryInterval + " ms");
sleepBeforeRecoveryAttempt();
lazyListen();
}
} else {
logger.error("SubscriptionTask aborted with exception:", ex);
}
}RedisMessageListenerContainer在jedis的subscribe抛异常时重新调用了lazyListen();试图重新加载监听线程
理论上来说当链接断开时只要底层jedis的subscribe处报异常时，spring-data-redis的RedisMessageListenerContainer的内部线程都应该处在异常->重连->异常->重连的循环之中。