Zookeeper-会话管理器SessionTracker

背景

Zookeeper中定义了SessionTracker接口用于管理Session

实现

由于将会话管理的实现代码抽象为ExpiryQueue,而ExpiryQueue的分析见:https://blog.csdn.net/jpf254/article/details/80800626

SessionTrackerImpl实现了SessionTracker,同时也继承了Thread,也是一个线程.其run()与NIOServerCnxnFactory.ConnectionExpirerThread.run()类似,代码如下:

    @Override
    public void run() {
        try {
            while (running) {
                long waitTime = sessionExpiryQueue.getWaitTime();
                if (waitTime > 0) {
                    Thread.sleep(waitTime);
                    continue;
                }

                for (SessionImpl s : sessionExpiryQueue.poll()) {
                    //1.标记会话状态为"closing"
                    setSessionClosing(s.sessionId);
                    //2.发起"会话关闭"请求
                    expirer.expire(s);
                }
            }
        } catch (InterruptedException e) {
            handleException(this.getName(), e);
        }
        LOG.info("SessionTrackerImpl exited loop!");
    }

    @Override
    synchronized public void setSessionClosing(long sessionId) {
        if (LOG.isTraceEnabled()) {
            LOG.trace("Session closing: 0x" + Long.toHexString(sessionId));
        }
        SessionImpl s = sessionsById.get(sessionId);
        if (s == null) {
            return;
        }
        s.isClosing = true;
    }

    @Override
    public void expire(Session session) {
        long sessionId = session.getSessionId();
        LOG.info("Expiring session 0x" + Long.toHexString(sessionId)
                + ", timeout of " + session.getTimeout() + "ms exceeded");
        close(sessionId);
    }

总结

参考