zookeeper源码学习-Vote

对象属性定义

private final int version;

    private final long id;

    private final long zxid;

    private final long electionEpoch;

    private final long peerEpoch;

实例化

 public Vote(long id, long zxid) {
        this.version = 0x0;
        this.id = id;
        this.zxid = zxid;
        this.electionEpoch = -1;
        this.peerEpoch = -1;
        this.state = ServerState.LOOKING;
    }

    public Vote(long id, long zxid, long peerEpoch) {
        this.version = 0x0;
        this.id = id;
        this.zxid = zxid;
        this.electionEpoch = -1;
        this.peerEpoch = peerEpoch;
        this.state = ServerState.LOOKING;
    }

    public Vote(long id, long zxid, long electionEpoch, long peerEpoch) {
        this.version = 0x0;
        this.id = id;
        this.zxid = zxid;
        this.electionEpoch = electionEpoch;
        this.peerEpoch = peerEpoch;
        this.state = ServerState.LOOKING;
    }

    public Vote(int version, long id, long zxid, long electionEpoch, long peerEpoch, ServerState state) {
        this.version = version;
        this.id = id;
        this.zxid = zxid;
        this.electionEpoch = electionEpoch;
        this.state = state;
        this.peerEpoch = peerEpoch;
    }

    public Vote(long id, long zxid, long electionEpoch, long peerEpoch, ServerState state) {
        this.id = id;
        this.zxid = zxid;
        this.electionEpoch = electionEpoch;
        this.state = state;
        this.peerEpoch = peerEpoch;
        this.version = 0x0;
    }

equals 判断是否相同

首先生成一个投票的实例，然后判断传进来的对象是否是投票

然后判断投票的状态，如果在要比较的节点或者传入的节点处于LOOKING状态，则比较所有的属性是否相同

如果不在LOOKING状态，则比较他们的id和朝代

public boolean equals(Object o) {
        if (!(o instanceof Vote)) {
            return false;
        }
        Vote other = (Vote) o;

        if ((state == ServerState.LOOKING) || (other.state == ServerState.LOOKING)) {
            return id == other.id
                   && zxid == other.zxid
                   && electionEpoch == other.electionEpoch
                   && peerEpoch == other.peerEpoch;
        } else {
            /*
             * There are two things going on in the logic below:
             *
             * 1. skip comparing the zxid and electionEpoch for votes for servers
             *    out of election.
             *
             *    Need to skip those because they can be inconsistent due to
             *    scenarios described in QuorumPeer.updateElectionVote.
             *
             *    And given that only one ensemble can be running at a single point
             *    in time and that each epoch is used only once, using only id and
             *    epoch to compare the votes is sufficient.
             *
             *    {@see https://issues.apache.org/jira/browse/ZOOKEEPER-1805}
             *
             * 2. skip comparing peerEpoch if if we're running with mixed ensemble
             *    with (version > 0x0) and without the change (version = 0x0)
             *    introduced in ZOOKEEPER-1732.
             *
             *    {@see https://issues.apache.org/jira/browse/ZOOKEEPER-1732}
             *
             *    The server running with and without ZOOKEEPER-1732 will return
             *    different peerEpoch. During rolling upgrades, it's possible
             *    that 2/5 servers are returning epoch 1, while the other 2/5
             *    are returning epoch 2, the other server need to ignore the
             *    peerEpoch to be able to join it.
             */
            if ((version > 0x0) ^ (other.version > 0x0)) {
                return id == other.id;
            } else {
                return (id == other.id && peerEpoch == other.peerEpoch);
            }
        }
    }