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MyCat配置信息
除了一些默认的配置参数，大多数的MyCat配置信息是通过读取若干.xml/.properties文件获取的，主要包括：
1）server.xml：系统和用户相关配置
2）schema.xml：虚拟库、表、数据节点配置等
3）rule.xml：分片规则设置
4）cacheservice.properties：缓存相关设置
5）dnindex.properties：datahost主从切换配置文件
6）sequence_conf.properties：本地全局序列号配置文件
而在代码层面，与配置相关的类主要包括3个：
1）MycatConfig：最为重要的配置类
2）ReloadConfig：用于通过管理端口执行mysql> reload @@config或config_all命令，重新载入配置文件
3）RollbackConfig：用于通过管理端口执行mysql> rollback @@config命令，将配置信息回滚至reload之前的状态
接下来重点介绍MycatConfig，它最关键的属性如下：
private volatile SystemConfig system; private volatile MycatCluster cluster; private volatile MycatCluster _cluster; private volatile QuarantineConfig quarantine; private volatile QuarantineConfig _quarantine; private volatile Map<String, UserConfig> users; private volatile Map<String, UserConfig> _users; private volatile Map<String, SchemaConfig> schemas; private volatile Map<String, SchemaConfig> _schemas; private volatile Map<String, PhysicalDBNode> dataNodes; private volatile Map<String, PhysicalDBNode> _dataNodes; private volatile Map<String, PhysicalDBPool> dataHosts; private volatile Map<String, PhysicalDBPool> _dataHosts;
- SystemConfig：包含了诸多系统相关的配置参数（如端口、编码、线程池大小、BufferPool大小、隔离级别等）
- MycatCluster：MyCat集群配置信息
- QuarantineConfig：用户权限隔离（黑白名单）
- UserConfig：用户配置，包含用户名/密码和允许访问的虚拟库
- SchemaConfig：虚拟库配置，包括所有下属的表配置（
TableConfig
）以及这些表涉及的datanode - PhysicalDBNode：datanode相关，对应一个数据库实例中的数据库
- PhysicalDBPool：datahost相关，里面包含了DataHostConfig配置，包括所有writeHosts和readHosts以及读写分离类型等
注意到除了SystemConfig，其余属性都还有一个前缀加了_的同名属性，这些属性其实是作为备份的，用于reload/rollback配置文件时的切换。reload和rollback相关的方法如下：
public void reload(Map<String, UserConfig> users, Map<String, SchemaConfig> schemas, Map<String, PhysicalDBNode> dataNodes, Map<String, PhysicalDBPool> dataHosts, MycatCluster cluster, QuarantineConfig quarantine,boolean reloadAll) { apply(users, schemas, dataNodes, dataHosts, cluster, quarantine,reloadAll); this.reloadTime = TimeUtil.currentTimeMillis(); this.status = reloadAll?RELOAD_ALL:RELOAD; } public void rollback(Map<String, UserConfig> users, Map<String, SchemaConfig> schemas, Map<String, PhysicalDBNode> dataNodes, Map<String, PhysicalDBPool> dataHosts, MycatCluster cluster, QuarantineConfig quarantine) { apply(users, schemas, dataNodes, dataHosts, cluster, quarantine,status==RELOAD_ALL); this.rollbackTime = TimeUtil.currentTimeMillis(); this.status = ROLLBACK; }
在reload的时候注意到有reload和reload_all，区别就在于前者不会重新加载与datahost/datanode相关的更改，而后者会。
启动流程
MyCat的启动类为MycatStartup，而主体为MycatServer，其中主要分为两个步骤：
1）初始化：此过程在MycatServer构造函数时执行，包括配置文件的读取、CacheService和RouteService的创建等
public MycatServer() { this.config = new MycatConfig(); this.timer = new Timer(NAME + "Timer", true); this.sqlRecorder = new SQLRecorder(config.getSystem() .getSqlRecordCount()); this.isOnline = new AtomicBoolean(true); cacheService = new CacheService(); routerService = new RouteService(cacheService); // load datanode active index from properties dnIndexProperties = loadDnIndexProps(); try { sqlInterceptor = (SQLInterceptor) Class.forName( config.getSystem().getSqlInterceptor()).newInstance(); } catch (Exception e) { throw new RuntimeException(e); } catletClassLoader = new DynaClassLoader(SystemConfig.getHomePath() + File.separator + "catlet", config.getSystem() .getCatletClassCheckSeconds()); this.startupTime = TimeUtil.currentTimeMillis(); }
2）运行：此过程由startup()方法触发，包括处理器对象创建、bufferpool创建、处理线程池创建、AIOConnector/NIOConnector创建与启动、两个AIOAcceptor/NIOAcceptor创建与启动、后端数据库的初始连接建立、定时器线程池/定时任务创建与启动
public void startup() throws IOException { SystemConfig system = config.getSystem(); int processorCount = system.getProcessors(); // server startup LOGGER.info("==============================================="); LOGGER.info(NAME + " is ready to startup ..."); String inf = "Startup processors ...,total processors:" + system.getProcessors() + ",aio thread pool size:" + system.getProcessorExecutor() + " each process allocated socket buffer pool " + " bytes ,buffer chunk size:" + system.getProcessorBufferChunk() + " buffer pool's capacity(buferPool/bufferChunk) is:" + system.getProcessorBufferPool() / system.getProcessorBufferChunk(); LOGGER.info(inf); LOGGER.info("sysconfig params:" + system.toString()); // startup manager ManagerConnectionFactory mf = new ManagerConnectionFactory(); ServerConnectionFactory sf = new ServerConnectionFactory(); SocketAcceptor manager = null; SocketAcceptor server = null; aio = (system.getUsingAIO() == 1); // startup processors int threadPoolSize = system.getProcessorExecutor(); processors = new NIOProcessor[processorCount]; long processBuferPool = system.getProcessorBufferPool(); int processBufferChunk = system.getProcessorBufferChunk(); int socketBufferLocalPercent = system.getProcessorBufferLocalPercent(); bufferPool = new BufferPool(processBuferPool, processBufferChunk, socketBufferLocalPercent / processorCount); businessExecutor = ExecutorUtil.create("BusinessExecutor", threadPoolSize); timerExecutor = ExecutorUtil.create("Timer", system.getTimerExecutor()); listeningExecutorService = MoreExecutors.listeningDecorator(businessExecutor); for (int i = 0; i < processors.length; i++) { processors[i] = new NIOProcessor("Processor" + i, bufferPool, businessExecutor); } if (aio) { LOGGER.info("using aio network handler "); asyncChannelGroups = new AsynchronousChannelGroup[processorCount]; // startup connector connector = new AIOConnector(); for (int i = 0; i < processors.length; i++) { asyncChannelGroups[i] = AsynchronousChannelGroup .withFixedThreadPool(processorCount, new ThreadFactory() { private int inx = 1; @Override public Thread newThread(Runnable r) { Thread th = new Thread(r); th.setName(BufferPool.LOCAL_BUF_THREAD_PREX + "AIO" + (inx++)); LOGGER.info("created new AIO thread " + th.getName()); return th; } }); } manager = new AIOAcceptor(NAME + "Manager", system.getBindIp(), system.getManagerPort(), mf, this.asyncChannelGroups[0]); // startup server server = new AIOAcceptor(NAME + "Server", system.getBindIp(), system.getServerPort(), sf, this.asyncChannelGroups[0]); } else { LOGGER.info("using nio network handler "); NIOReactorPool reactorPool = new NIOReactorPool( BufferPool.LOCAL_BUF_THREAD_PREX + "NIOREACTOR", processors.length); connector = new NIOConnector(BufferPool.LOCAL_BUF_THREAD_PREX + "NIOConnector", reactorPool); ((NIOConnector) connector).start(); manager = new NIOAcceptor(BufferPool.LOCAL_BUF_THREAD_PREX + NAME + "Manager", system.getBindIp(), system.getManagerPort(), mf, reactorPool); server = new NIOAcceptor(BufferPool.LOCAL_BUF_THREAD_PREX + NAME + "Server", system.getBindIp(), system.getServerPort(), sf, reactorPool); } // manager start manager.start(); LOGGER.info(manager.getName() + " is started and listening on " + manager.getPort()); server.start(); // server started LOGGER.info(server.getName() + " is started and listening on " + server.getPort()); LOGGER.info("==============================================="); // init datahost Map<String, PhysicalDBPool> dataHosts = config.getDataHosts(); LOGGER.info("Initialize dataHost ..."); for (PhysicalDBPool node : dataHosts.values()) { String index = dnIndexProperties.getProperty(node.getHostName(), "0"); if (!"0".equals(index)) { LOGGER.info("init datahost: " + node.getHostName() + " to use datasource index:" + index); } node.init(Integer.valueOf(index)); node.startHeartbeat(); } long dataNodeIldeCheckPeriod = system.getDataNodeIdleCheckPeriod(); timer.schedule(updateTime(), 0L, TIME_UPDATE_PERIOD); timer.schedule(processorCheck(), 0L, system.getProcessorCheckPeriod()); timer.schedule(dataNodeConHeartBeatCheck(dataNodeIldeCheckPeriod), 0L, dataNodeIldeCheckPeriod); timer.schedule(dataNodeHeartbeat(), 0L, system.getDataNodeHeartbeatPeriod()); timer.schedule(catletClassClear(), 30000); }
从以上代码中不难看出，connector用于作为客户端与后端MySQL建立连接，而server和manager则作为服务端接受来自前端应用的连接请求，其中server负责常规业务流程（默认端口8066），而manager负责监控与管理（默认端口9066）。
而datahost的初始化行为由node.init(Integer.valueOf(index));触发，其目的是每个datahost中writehost会连续创建若干初始连接供使用（该数量由schema.xml中datahost标签的minCon属性确定），当后续连接不足时会创建新的连接（最大不超过maxCon）。
由此，MyCat程序启动完成，等待接受来自应用的连接请求和后续的命令处理。
为尊重原创成果，如需转载烦请注明本文出处：http://www.cnblogs.com/fernandolee24/p/5193983.html，特此感谢