纯干货 | Dolphinscheduler Master模块源码剖析-编程知识

纯干货 | Dolphinscheduler Master模块源码剖析

news/2025/4/2 6:01:36/文章来源:https://www.cnblogs.com/DolphinScheduler/p/18802071

此前我们曾用万字长文解释了Apache DolphinScheduler的Worker模块源码，今天，我们再来一起看看Master模块源码的原理。

Master Slot计算

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核心代码逻辑：
org.apache.dolphinscheduler.server.master.registry.MasterSlotManager.SlotChangeListener#notify

public void notify(Map<String, MasterHeartBeat> masterNodeInfo) {List<Server> serverList = masterNodeInfo.values().stream()// TODO 这里其实就是过滤掉buzy的master节点.filter(heartBeat -> !heartBeat.getServerStatus().equals(ServerStatus.BUSY)).map(this::convertHeartBeatToServer).collect(Collectors.toList());// TODO 同步master节点syncMasterNodes(serverList);
}

计算 totalSlot和currentSlot

private void syncMasterNodes(List<Server> masterNodes) {slotLock.lock();try {this.masterPriorityQueue.clear();// TODO 这里会把所有的master节点都放入到masterPriorityQueue中，比如说 [192.168.220.1:12345,192.168.220.2:12345]this.masterPriorityQueue.putAll(masterNodes);// TODO 就是获取到本地ip的在队列中的位置int tempCurrentSlot = masterPriorityQueue.getIndex(masterConfig.getMasterAddress());// TODO 所有节点数量int tempTotalSlot = masterNodes.size();// TODO 正常情况下不会小于0if (tempCurrentSlot < 0) {totalSlot = 0;currentSlot = 0;log.warn("Current master is not in active master list");} else if (tempCurrentSlot != currentSlot || tempTotalSlot != totalSlot) {// TODO 这里其实就是记录的是比如说一共有两个slot，我的slot是0或者1totalSlot = tempTotalSlot;currentSlot = tempCurrentSlot;log.info("Update master nodes, total master size: {}, current slot: {}", totalSlot, currentSlot);}} finally {slotLock.unlock();}
}

this.masterPriorityQueue.putAll(masterNodes); 会计算索引

public void putAll(Collection<Server> serverList) {for (Server server : serverList) {this.queue.put(server);}// TODO 这里更新了hostIndexMap，存放的是 <host:port> -> 索引refreshMasterList();
}private void refreshMasterList() {hostIndexMap.clear();Iterator<Server> iterator = queue.iterator();int index = 0;while (iterator.hasNext()) {Server server = iterator.next();String addr = NetUtils.getAddr(server.getHost(), server.getPort());hostIndexMap.put(addr, index);index += 1;}}

Master消费Command生成流程实例

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command最终的获取逻辑:

比如说两个Master节点 : 
masterCount=2 thisMasterSlot=0  master1
masterCount=2 thisMasterSlot=1  master2command中的数据如下 :
1 master2
2 master1
3 master2
4 master1select *from t_ds_commandwhere id % #{masterCount} = #{thisMasterSlot}order by process_instance_priority, id asclimit #{limit}

有没有感到疑惑，就是如果一个master更新到的最新的，一个没有更新到，怎么办？

比如说，master1节点是这样的
1  master2
2  master1
3  master2
4  master1比如说，master2节点是这样的，是不是发现master2节点都是他的，都可以拉取消费？那就导致重复消费，比如说1这个command
1 master1
2 master1
3 master1
4 master1

org.apache.dolphinscheduler.service.process.ProcessServiceImpl#handleCommand

@Transactional
public @Nullable ProcessInstance handleCommand(String host,Command command) throws CronParseException, CodeGenerateException {// TODO 创建流程实例ProcessInstance processInstance = constructProcessInstance(command, host);// cannot construct process instance, return nullif (processInstance == null) {log.error("scan command, command parameter is error: {}", command);commandService.moveToErrorCommand(command, "process instance is null");return null;}processInstance.setCommandType(command.getCommandType());processInstance.addHistoryCmd(command.getCommandType());processInstance.setTestFlag(command.getTestFlag());// if the processDefinition is serialProcessDefinition processDefinition = this.findProcessDefinition(processInstance.getProcessDefinitionCode(),processInstance.getProcessDefinitionVersion());// TODO 是否是串行执行if (processDefinition.getExecutionType().typeIsSerial()) {saveSerialProcess(processInstance, processDefinition);if (processInstance.getState() != WorkflowExecutionStatus.RUNNING_EXECUTION) {setSubProcessParam(processInstance);triggerRelationService.saveProcessInstanceTrigger(command.getId(), processInstance.getId());deleteCommandWithCheck(command.getId());// todo: this is a bad design to return null here, whether trigger the taskreturn null;}} else {// TODO 并行执行processInstanceDao.upsertProcessInstance(processInstance);}// TODO 这里其实还会向triggerRelation表中插入一条数据，是流程实例和triggerCode的关系triggerRelationService.saveProcessInstanceTrigger(command.getId(), processInstance.getId());// TODO 设置子流程参数setSubProcessParam(processInstance);// TODO 删除commanddeleteCommandWithCheck(command.getId());return processInstance;
}

注意：这个方法是加@Transactional的，所以说创建流程实例和删除Command是在一个事物里面的，如果不同的Master消费到同一个Command。肯定会有一个删除Command失败，这时会抛出一个异常，这样就会让数据库进行回滚。

工作流启动流程

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DAG切分 & 任务提交

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Master事件状态流转

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图连接 : Master事件状态流转

TaskEventService组件中的TaskEventDispatchThread(线程)和TaskEventHandlerThread(线程)解析

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其实就是Master自己状态(DISPATCH)和Worker汇报上来的状态(RUNNING、UPDATE_PID、RESULT)都会放入到eventQueue，TaskEventDispatchThread(线程)会阻塞的方式进行获取，然后放入到对应的TaskExecuteRunnable中(注意 : 不执行的)，只有通过TaskEventHandlerThread(线程)才会使用TaskExecuteThreadPool线程进行TaskExecuteRunnable的提交。

转载自Journey
原文链接：https://segmentfault.com/a/1190000044992842