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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()
+ " \r\n 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