要講zookeeper的引數配置，可以從程式碼層面說起，在zookeeper中有一個類，QuorumPeerMain類。

其main方法如下：

    public static void main(String[] args) {
        QuorumPeerMain main = new QuorumPeerMain();
        try {
            main.initializeAndRun(args);
        } catch (IllegalArgumentException e) {
            LOG.error("Invalid arguments, exiting abnormally", e);
            LOG.info(USAGE);
            System.err.println(USAGE);
            System.exit(2);
        } catch (ConfigException e) {
            LOG.error("Invalid config, exiting abnormally", e);
            System.err.println("Invalid config, exiting abnormally");
            System.exit(2);
        } catch (Exception e) {
            LOG.error("Unexpected exception, exiting abnormally", e);
            System.exit(1);
        }
        LOG.info("Exiting normally");
        System.exit(0);
    }
 

    protected void initializeAndRun(String[] args)
        throws ConfigException, IOException
    {
        QuorumPeerConfig config = new QuorumPeerConfig();
        if (args.length == 1) {
            config.parse(args[0]);
        }

        // Start and schedule the the purge task
        DatadirCleanupManager purgeMgr = new DatadirCleanupManager(config
                .getDataDir(), config.getDataLogDir(), config
                .getSnapRetainCount(), config.getPurgeInterval());
        purgeMgr.start();

        if (args.length == 1 && config.servers.size() > 0) {
            runFromConfig(config);
        } else {
            LOG.warn("Either no config or no quorum defined in config, running "
                    + " in standalone mode");
            // there is only server in the quorum -- run as standalone
            ZooKeeperServerMain.main(args);
        }
    }
 

    public void parse(String path) throws ConfigException {
        File configFile = new File(path);

        LOG.info("Reading configuration from: " + configFile);

        try {
            if (!configFile.exists()) {
                throw new IllegalArgumentException(configFile.toString()
                        + " file is missing");
            }

            Properties cfg = new Properties();
            FileInputStream in = new FileInputStream(configFile);
            try {
                cfg.load(in);
            } finally {
                in.close();
            }

            parseProperties(cfg);
 

        } catch (IOException e) {
            throw new ConfigException("Error processing " + path, e);
        } catch (IllegalArgumentException e) {
            throw new ConfigException("Error processing " + path, e);
        }
    }

public void parseProperties(Properties zkProp)
    throws IOException, ConfigException {
        int clientPort = 0;
        String clientPortAddress = null;
        for (Entry<Object, Object> entry : zkProp.entrySet()) {
            String key = entry.getKey().toString().trim();
            String value = entry.getValue().toString().trim();
            if (key.equals("dataDir")) {
                dataDir = value;
            } else if (key.equals("dataLogDir")) {
                dataLogDir = value;
            } else if (key.equals("clientPort")) {
                clientPort = Integer.parseInt(value);
            } else if (key.equals("clientPortAddress")) {
                clientPortAddress = value.trim();
            } else if (key.equals("tickTime")) {
                tickTime = Integer.parseInt(value);
            } else if (key.equals("maxClientCnxns")) {
                maxClientCnxns = Integer.parseInt(value);
            } else if (key.equals("minSessionTimeout")) {
                minSessionTimeout = Integer.parseInt(value);
            } else if (key.equals("maxSessionTimeout")) {
                maxSessionTimeout = Integer.parseInt(value);
            } else if (key.equals("initLimit")) {
                initLimit = Integer.parseInt(value);
            } else if (key.equals("syncLimit")) {
                syncLimit = Integer.parseInt(value);
            } else if (key.equals("electionAlg")) {
                electionAlg = Integer.parseInt(value);
            } else if (key.equals("quorumListenOnAllIPs")) {
                quorumListenOnAllIPs = Boolean.parseBoolean(value);
            } else if (key.equals("peerType")) {
                if (value.toLowerCase().equals("observer")) {
                    peerType = LearnerType.OBSERVER;
                } else if (value.toLowerCase().equals("participant")) {
                    peerType = LearnerType.PARTICIPANT;
                } else
                {
                    throw new ConfigException("Unrecognised peertype: " + value);
                }
            } else if (key.equals( "syncEnabled" )) {
                syncEnabled = Boolean.parseBoolean(value);
            } else if (key.equals("autopurge.snapRetainCount")) {
                snapRetainCount = Integer.parseInt(value);
            } else if (key.equals("autopurge.purgeInterval")) {
                purgeInterval = Integer.parseInt(value);
            } else if (key.startsWith("server.")) {
                int dot = key.indexOf('.');
                long sid = Long.parseLong(key.substring(dot + 1));
                String parts[] = value.split(":");
                if ((parts.length != 2) && (parts.length != 3) && (parts.length !=4)) {
                    LOG.error(value
                       + " does not have the form host:port or host:port:port " +
                       " or host:port:port:type");
                }
                InetSocketAddress addr = new InetSocketAddress(parts[0],
                        Integer.parseInt(parts[1]));
                if (parts.length == 2) {
                    servers.put(Long.valueOf(sid), new QuorumServer(sid, addr));
                } else if (parts.length == 3) {
                    InetSocketAddress electionAddr = new InetSocketAddress(
                            parts[0], Integer.parseInt(parts[2]));
                    servers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
                            electionAddr));
                } else if (parts.length == 4) {
                    InetSocketAddress electionAddr = new InetSocketAddress(
                            parts[0], Integer.parseInt(parts[2]));
                    LearnerType type = LearnerType.PARTICIPANT;
                    if (parts[3].toLowerCase().equals("observer")) {
                        type = LearnerType.OBSERVER;
                        observers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
                                electionAddr,type));
                    } else if (parts[3].toLowerCase().equals("participant")) {
                        type = LearnerType.PARTICIPANT;
                        servers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
                                electionAddr,type));
                    } else {
                        throw new ConfigException("Unrecognised peertype: " + value);
                    }
                }
            } else if (key.startsWith("group")) {
                int dot = key.indexOf('.');
                long gid = Long.parseLong(key.substring(dot + 1));

                numGroups++;

                String parts[] = value.split(":");
                for(String s : parts){
                    long sid = Long.parseLong(s);
                    if(serverGroup.containsKey(sid))
                        throw new ConfigException("Server " + sid + "is in multiple groups");
                    else
                        serverGroup.put(sid, gid);
                }

            } else if(key.startsWith("weight")) {
                int dot = key.indexOf('.');
                long sid = Long.parseLong(key.substring(dot + 1));
                serverWeight.put(sid, Long.parseLong(value));
            } else {
                System.setProperty("zookeeper." + key, value);
            }
        }

至此zookeeper讀取配置的原始碼就解析完成了