zookeeper源码学习-SyncedLearnerTracker

该类主要的功能是记录节点ack的信息，并且判断是否超过了半数等信息

这个东西是在FastleaderElection中通过getVoteTracker获取到的

关系图

变量

protected ArrayList<QuorumVerifierAcksetPair> qvAcksetPairs = new ArrayList<QuorumVerifierAcksetPair>();

只有一个变量，节点验证器的ack集合，所以重点是这个qvAcksetPairs

QuorumVerifierAcksetPair

用来存储验证器，以及ack的列表。

public static class QuorumVerifierAcksetPair {

        private final QuorumVerifier qv;   //验证器
        private final HashSet<Long> ackset;   //ack的列表

        public QuorumVerifierAcksetPair(QuorumVerifier qv, HashSet<Long> ackset) {
            this.qv = qv;
            this.ackset = ackset;
        }

        public QuorumVerifier getQuorumVerifier() {
            return this.qv;
        }

        public HashSet<Long> getAckset() {
            return this.ackset;
        }

    }

hasAllQuorums 核心功能，用来判断是否满足了Quorum机制

如果其中存在某个验证器没有拿到超过半数的机器的ack，则认为是失败的。

public boolean hasAllQuorums() {
        for (QuorumVerifierAcksetPair qvAckset : qvAcksetPairs) {
            if (!qvAckset.getQuorumVerifier().containsQuorum(qvAckset.getAckset())) {
                return false;
            }
        }
        return true;
    }

public class SyncedLearnerTracker {

    protected ArrayList<QuorumVerifierAcksetPair> qvAcksetPairs = new ArrayList<QuorumVerifierAcksetPair>();

    public void addQuorumVerifier(QuorumVerifier qv) {
        qvAcksetPairs.add(new QuorumVerifierAcksetPair(qv, new HashSet<Long>(qv.getVotingMembers().size())));
    }

    public boolean addAck(Long sid) {
        boolean change = false;
        for (QuorumVerifierAcksetPair qvAckset : qvAcksetPairs) {
            if (qvAckset.getQuorumVerifier().getVotingMembers().containsKey(sid)) {
                qvAckset.getAckset().add(sid);
                change = true;
            }
        }
        return change;
    }

    public boolean hasSid(long sid) {
        for (QuorumVerifierAcksetPair qvAckset : qvAcksetPairs) {
            if (!qvAckset.getQuorumVerifier().getVotingMembers().containsKey(sid)) {
                return false;
            }
        }
        return true;
    }

    public boolean hasAllQuorums() {
        for (QuorumVerifierAcksetPair qvAckset : qvAcksetPairs) {
            if (!qvAckset.getQuorumVerifier().containsQuorum(qvAckset.getAckset())) {
                return false;
            }
        }
        return true;
    }

    public String ackSetsToString() {
        StringBuilder sb = new StringBuilder();

        for (QuorumVerifierAcksetPair qvAckset : qvAcksetPairs) {
            sb.append(qvAckset.getAckset().toString()).append(",");
        }

        return sb.substring(0, sb.length() - 1);
    }

    public static class QuorumVerifierAcksetPair {

        private final QuorumVerifier qv;
        private final HashSet<Long> ackset;

        public QuorumVerifierAcksetPair(QuorumVerifier qv, HashSet<Long> ackset) {
            this.qv = qv;
            this.ackset = ackset;
        }

        public QuorumVerifier getQuorumVerifier() {
            return this.qv;
        }

        public HashSet<Long> getAckset() {
            return this.ackset;
        }

    }

}