zookeeper源码学习-读取配置文件

parseDynamicConfig 读取配置文件，返回QuorumVerifier，包含所有节点的信息

对节点的配置，需要是用server.开头，或者是version开头

拿到QV之后，根据参与者的数量，做一些校验

如果校验通过，在返回的QV里面，包含所有的节点的信息，方便后续进行选举时候的连接

里面有两个核心的东西，lastSeenQuorumVerifier和quorumVerifier

public static QuorumVerifier parseDynamicConfig(Properties dynamicConfigProp, int eAlg, boolean warnings, boolean configBackwardCompatibilityMode) throws IOException, ConfigException {
        boolean isHierarchical = false;
        for (Entry<Object, Object> entry : dynamicConfigProp.entrySet()) {
            String key = entry.getKey().toString().trim();
            if (key.startsWith("group") || key.startsWith("weight")) {
                isHierarchical = true;
            } else if (!configBackwardCompatibilityMode && !key.startsWith("server.") && !key.equals("version")) {
                LOG.info(dynamicConfigProp.toString());
                throw new ConfigException("Unrecognised parameter: " + key);
            }
        }

        QuorumVerifier qv = createQuorumVerifier(dynamicConfigProp, isHierarchical);

        int numParticipators = qv.getVotingMembers().size();
        int numObservers = qv.getObservingMembers().size();
        if (numParticipators == 0) {
            if (!standaloneEnabled) {
                throw new IllegalArgumentException("standaloneEnabled = false then "
                                                   + "number of participants should be >0");
            }
            if (numObservers > 0) {
                throw new IllegalArgumentException("Observers w/o participants is an invalid configuration");
            }
        } else if (numParticipators == 1 && standaloneEnabled) {
            // HBase currently adds a single server line to the config, for
            // b/w compatibility reasons we need to keep this here. If standaloneEnabled
            // is true, the QuorumPeerMain script will create a standalone server instead
            // of a quorum configuration
            LOG.error("Invalid configuration, only one server specified (ignoring)");
            if (numObservers > 0) {
                throw new IllegalArgumentException("Observers w/o quorum is an invalid configuration");
            }
        } else {
            if (warnings) {
                if (numParticipators <= 2) {
                    LOG.warn("No server failure will be tolerated. You need at least 3 servers.");
                } else if (numParticipators % 2 == 0) {
                    LOG.warn("Non-optimial configuration, consider an odd number of servers.");
                }
            }

            for (QuorumServer s : qv.getVotingMembers().values()) {
                if (s.electionAddr == null) {
                    throw new IllegalArgumentException("Missing election port for server: " + s.id);
                }
            }
        }
        return qv;
    }

createQuorumVerifier 创建QuorumVerifier

private static QuorumVerifier createQuorumVerifier(Properties dynamicConfigProp, boolean isHierarchical) throws ConfigException {
        if (isHierarchical) {
            return new QuorumHierarchical(dynamicConfigProp);
        } else {
            /*
             * The default QuorumVerifier is QuorumMaj
             */
            //LOG.info("Defaulting to majority quorums");
            return new QuorumMaj(dynamicConfigProp);
        }
    }

QuorumMaj 根据配置文件，返回一个QuorumVerifier，并且规定根据节点类型不同，加入到不同的set中，最后根据投票set的大小，计算出来Quorum的判定值

public QuorumMaj(Properties props) throws ConfigException {
        for (Entry<Object, Object> entry : props.entrySet()) {
            String key = entry.getKey().toString();
            String value = entry.getValue().toString();

            if (key.startsWith("server.")) {  
                int dot = key.indexOf('.');
                long sid = Long.parseLong(key.substring(dot + 1));
                QuorumServer qs = new QuorumServer(sid, value);
                allMembers.put(Long.valueOf(sid), qs);
                if (qs.type == LearnerType.PARTICIPANT) {
                    votingMembers.put(Long.valueOf(sid), qs);
                } else {
                    observingMembers.put(Long.valueOf(sid), qs);
                }
            } else if (key.equals("version")) {
                version = Long.parseLong(value, 16);
            }
        }
        half = votingMembers.size() / 2;
    }