zookeeper源码学习-QuorumCnxManager

原本的代码很长，只记录了个别在看代码时候有用的一些

里面会启动两个线程，一个发送线程QuorumConnectionReqThread还有一个接受线程QuorumConnectionReceiverThread。
在zk启动的时候，会在QuorumConfig里面读到所有的节点信息，然后生成一个Quorum验证器，这时候已经包含了所有的节点信息。
然后是一些节点数据或者投票的发送，已经接到返回时候的相关处理，这个没有仔细研究，有兴趣的可以去看下QuorumCnxManager的源码

消息的发送

public void toSend(Long sid, ByteBuffer b) {
        /*
         * If sending message to myself, then simply enqueue it (loopback).
         */
        if (this.mySid == sid) {    //如果当前的消息需要分给自己，那么就直接把它放入到接收队列中
            b.position(0);
            addToRecvQueue(new Message(b.duplicate(), sid));
            /*
             * Otherwise send to the corresponding thread to send.
             */
        } else {
            /*
             * Start a new connection if doesn't have one already.
             */
            BlockingQueue<ByteBuffer> bq = queueSendMap.computeIfAbsent(sid, serverId -> new CircularBlockingQueue<>(SEND_CAPACITY));
            addToSendQueue(bq, b);
            connectOne(sid);
        }
    }

建立连接

synchronized void connectOne(long sid) {
        if (senderWorkerMap.get(sid) != null) {
            LOG.debug("There is a connection already for server {}", sid);
            if (self.isMultiAddressEnabled() && self.isMultiAddressReachabilityCheckEnabled()) {
                // since ZOOKEEPER-3188 we can use multiple election addresses to reach a server. It is possible, that the
                // one we are using is already dead and we need to clean-up, so when we will create a new connection
                // then we will choose an other one, which is actually reachable
                senderWorkerMap.get(sid).asyncValidateIfSocketIsStillReachable();
            }
            return;
        }
        synchronized (self.QV_LOCK) {
            boolean knownId = false;
            // Resolve hostname for the remote server before attempting to
            // connect in case the underlying ip address has changed.
            self.recreateSocketAddresses(sid);
            Map<Long, QuorumPeer.QuorumServer> lastCommittedView = self.getView();
            QuorumVerifier lastSeenQV = self.getLastSeenQuorumVerifier();
            Map<Long, QuorumPeer.QuorumServer> lastProposedView = lastSeenQV.getAllMembers();
            if (lastCommittedView.containsKey(sid)) {
                knownId = true;
                LOG.debug("Server {} knows {} already, it is in the lastCommittedView", self.getId(), sid);
                if (connectOne(sid, lastCommittedView.get(sid).electionAddr)) {
                    return;
                }
            }
            if (lastSeenQV != null
                && lastProposedView.containsKey(sid)
                && (!knownId
                    || (lastProposedView.get(sid).electionAddr != lastCommittedView.get(sid).electionAddr))) {
                knownId = true;
                LOG.debug("Server {} knows {} already, it is in the lastProposedView", self.getId(), sid);

                if (connectOne(sid, lastProposedView.get(sid).electionAddr)) {
                    return;
                }
            }
            if (!knownId) {
                LOG.warn("Invalid server id: {} ", sid);
            }
        }
    }