[bug fix]fix bug: After the master is fault-tolerant, it cannot resume operation (#2813)

* feature: add number configuration for master dispatch tasks

* fix bug(#2762) the master would be blocked when worker group not exists

* fix bug(#2762) the master would be blocked when worker group not exists

* fix ut

* fix ut

* fix bug(2781): cannot pause work flow when task state is "submit success"

* fix code smell

* add mysql other param blank judge

* test

* update comments

* update comments

* add ut

* fix bug: Restart the worker service again, the previously submitted successful tasks are not executed

* update comments

* add sleep

* add null point check

* fix bug:After the master is fault-tolerant, it cannot resume operation

* fix bug: do not failover the host is 'NULL' process
Co-authored-by: Nbaoliang <baoliang@analysys.com.cn>

dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/zk/ZKMasterClient.java

@@ -335,6 +335,9 @@ public class ZKMasterClient extends AbstractZKClient {
 
 		//updateProcessInstance host is null and insert into command
 		for(ProcessInstance processInstance : needFailoverProcessInstanceList){
+			if(Constants.NULL.equals(processInstance.getHost()) ){
+			    continue;
+			}
 			processService.processNeedFailoverProcessInstances(processInstance);
 		}
 

dolphinscheduler-service/src/main/java/org/apache/dolphinscheduler/service/process/ProcessService.java

@@ -121,10 +121,6 @@ public class ProcessService {
             logger.info("there is not enough thread for this command: {}", command);
             return setWaitingThreadProcess(command, processInstance);
         }
-        if (processInstance.getCommandType().equals(CommandType.RECOVER_TOLERANCE_FAULT_PROCESS)){
-            delCommandByid(command.getId());
-            return null;
-        }
         processInstance.setCommandType(command.getCommandType());
         processInstance.addHistoryCmd(command.getCommandType());
         saveProcessInstance(processInstance);
@@ -1484,7 +1480,7 @@ public class ProcessService {
     @Transactional(rollbackFor = Exception.class)
     public void processNeedFailoverProcessInstances(ProcessInstance processInstance){
         //1 update processInstance host is null
-        processInstance.setHost("null");
+        processInstance.setHost(Constants.NULL);
         processInstanceMapper.updateById(processInstance);
 
         //2 insert into recover command

dolphinscheduler-service/src/main/java/org/apache/dolphinscheduler/service/zk/AbstractZKClient.java

@@ -125,12 +125,16 @@ public abstract class AbstractZKClient extends ZookeeperCachedOperator {
 		List<Server> masterServers = new ArrayList<>();
 		for (Map.Entry<String, String> entry : masterMap.entrySet()) {
 			Server masterServer = ResInfo.parseHeartbeatForZKInfo(entry.getValue());
+			if(masterServer == null){
+				continue;
+			}
 			String key = entry.getKey();
 			masterServer.setZkDirectory(parentPath + "/"+ key);
 			//set host and port
 			String[] hostAndPort=key.split(COLON);
 			String[] hosts=hostAndPort[0].split(DIVISION_STRING);
-			masterServer.setHost(hosts[hosts.length-1]);// fetch the last one
+			// fetch the last one
+			masterServer.setHost(hosts[hosts.length-1]);
 			masterServer.setPort(Integer.parseInt(hostAndPort[1]));
 			masterServers.add(masterServer);
 		}