海豚调度Dolphinscheduler源码分析（四）
今天来分析server模块的master，MasterServer类
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package org.apache.dolphinscheduler.server.master;
import org.apache.dolphinscheduler.common.Constants;
import org.apache.dolphinscheduler.common.thread.Stopper;
import org.apache.dolphinscheduler.remote.NettyRemotingServer;
import org.apache.dolphinscheduler.remote.command.CommandType;
import org.apache.dolphinscheduler.remote.config.NettyServerConfig;
import org.apache.dolphinscheduler.server.master.config.MasterConfig;
import org.apache.dolphinscheduler.server.master.processor.TaskAckProcessor;
import org.apache.dolphinscheduler.server.master.processor.TaskKillResponseProcessor;
import org.apache.dolphinscheduler.server.master.processor.TaskResponseProcessor;
import org.apache.dolphinscheduler.server.master.registry.MasterRegistry;
import org.apache.dolphinscheduler.server.master.runner.MasterSchedulerService;
import org.apache.dolphinscheduler.server.worker.WorkerServer;
import org.apache.dolphinscheduler.server.zk.ZKMasterClient;
import org.apache.dolphinscheduler.service.bean.SpringApplicationContext;
import org.apache.dolphinscheduler.service.quartz.QuartzExecutors;
import org.quartz.SchedulerException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.FilterType;
import javax.annotation.PostConstruct;
@ComponentScan(value = "org.apache.dolphinscheduler", excludeFilters = {
@ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, classes = {WorkerServer.class})
})
public class MasterServer {
/**
* logger of MasterServer
*/
private static final Logger logger = LoggerFactory.getLogger(MasterServer.class);
/**
* master config
* master 配置类注入
*/
@Autowired
private MasterConfig masterConfig;
/**
* spring application context
* only use it for initialization
* 仅用于初始化
*/
@Autowired
private SpringApplicationContext springApplicationContext;
/**
* 网络远程服务器
* netty remote server
*/
private NettyRemotingServer nettyRemotingServer;
/**
* master registry
* master服务监听
*/
@Autowired
private MasterRegistry masterRegistry;
/**
* zk master client
* zk 客户端curator
*/
@Autowired
private ZKMasterClient zkMasterClient;
/**
* scheduler service
*/
@Autowired
private MasterSchedulerService masterSchedulerService;
/**
* master server startup
*
* master server not use web service
* @param args arguments
*/
public static void main(String[] args) {
Thread.currentThread().setName(Constants.THREAD_NAME_MASTER_SERVER);
new SpringApplicationBuilder(MasterServer.class).web(WebApplicationType.NONE).run(args);
}
/**
* run master server
* @PostConstruct 会在该bean依赖注入完成后，执行该方法
*/
@PostConstruct
public void run(){
//init remoting server
//初始化 netty 服务器
NettyServerConfig serverConfig = new NettyServerConfig();
serverConfig.setListenPort(masterConfig.getListenPort());
this.nettyRemotingServer = new NettyRemotingServer(serverConfig);
this.nettyRemotingServer.registerProcessor(CommandType.TASK_EXECUTE_RESPONSE, new TaskResponseProcessor());
this.nettyRemotingServer.registerProcessor(CommandType.TASK_EXECUTE_ACK, new TaskAckProcessor());
this.nettyRemotingServer.registerProcessor(CommandType.TASK_KILL_RESPONSE, new TaskKillResponseProcessor());
this.nettyRemotingServer.start();
// register
// 添加node/master/XXX:5678节点，并监听事件
this.masterRegistry.registry();
// self tolerant
// 这个地方有个分布式锁，保持/dolphinscheduler/lock/failover/startup-masters
// 锁，然后创建znode节点，
// 并查询master任务和worker任务是否需要容错
this.zkMasterClient.start();
// scheduler start
// 启动master scheduler
// MasterSchedulerService，继承了Thread类
this.masterSchedulerService.start();
// start QuartzExecutors
// what system should do if exception
try {
logger.info("start Quartz server...");
// 开启quartzExecutor 服务
QuartzExecutors.getInstance().start();
} catch (Exception e) {
try {
QuartzExecutors.getInstance().shutdown();
} catch (SchedulerException e1) {
logger.error("QuartzExecutors shutdown failed : " + e1.getMessage(), e1);
}
logger.error("start Quartz failed", e);
}
/**
* register hooks, which are called before the process exits，在关闭程序时，jvm会先执行close方法
*/
Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
@Override
public void run() {
close("shutdownHook");
}
}));
}
/**
* gracefully close
* @param cause close cause
*/
public void close(String cause) {
try {
//execute only once
if(Stopper.isStopped()){
return;
}
logger.info("master server is stopping ..., cause : {}", cause);
// set stop signal is true
Stopper.stop();
try {
//thread sleep 3 seconds for thread quietly stop
Thread.sleep(3000L);
}catch (Exception e){
logger.warn("thread sleep exception ", e);
}
//
this.masterSchedulerService.close();
this.nettyRemotingServer.close();
this.masterRegistry.unRegistry();
this.zkMasterClient.close();
//close quartz
try{
QuartzExecutors.getInstance().shutdown();
logger.info("Quartz service stopped");
}catch (Exception e){
logger.warn("Quartz service stopped exception:{}",e.getMessage());
}
} catch (Exception e) {
logger.error("master server stop exception ", e);
System.exit(-1);
}
}
}
有两个点 需要看一下：
一：Runtime.getRuntime().addShutdownHook(shutdownHook);
Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
@Override
public void run() {
close("shutdownHook");
}
}));
这个方法的含义说明：
这个方法的意思就是在jvm中增加一个关闭的钩子，当jvm关闭的时候，会执行系统中已经设置的所有通过方法addShutdownHook添加的钩子，当系统执行完这些钩子后，jvm才会关闭。所以这些钩子可以在jvm关闭的时候进行内存清理、对象销毁等操作。
二：PostConstruct
public static void main(String[] args) {
Thread.currentThread().setName(Constants.THREAD_NAME_MASTER_SERVER);
new SpringApplicationBuilder(MasterServer.class).web(WebApplicationType.NONE).run(args);
}
/**
* run master server
* @PostConstruct 会在该bean依赖注入完成后，执行该方法
*/
@PostConstruct
public void run(){
//init remoting server
//初始化 netty 服务器
NettyServerConfig serverConfig = new NettyServerConfig();
serverConfig.setListenPort(masterConfig.getListenPort());
this.nettyRemotingServer.start();
// register
// 添加node/master/XXX:5678节点，并监听事件
this.masterRegistry.registry();
}
在main方法中调用了MasterServer.class 此时构造方法还无法完成初始化，需要借助@PostConstruct，通过run()方法，完成MasterServer类的
对象的初始化。
这个参考https://www.cnblogs.com/erlou96/p/13753824.html