App Timeline Server not started from ambari

[#1]

hi all

when we perform restart of the services in the ambari , we get the following exception

and from ambari we can see that - App Timeline Server cant start

what is the meaning of - "Cannot set permission for /ats/done. Name node is in safe mode.\nThe reported blocks 26 needs additional 2 blocks to reach the threshold 0.9900 of total blocks 28.\nThe number of live datanodes 3 has reached the minimum number 0. Safe mode will be turned off automatically once the thresholds have been reached"

{
  "RemoteException": {
    "exception": "RetriableException", 
    "javaClassName": "org.apache.hadoop.ipc.RetriableException", 
    "message": "org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot set permission for /ats/done. Name node is in safe mode.\nThe reported blocks 26 needs additional 2 blocks to reach the threshold 0.9900 of total blocks 28.\nThe number of live datanodes 3 has reached the minimum number 0. Safe mode will be turned off automatically once the thresholds have been reached."
  }
}

[#2]

@mike_bronson7 

ATS needs to reed files for HDFS and set the permissions as the Namenode isn't started there is no way the ATS file location can be passed to successfully start the service you will need to do the following as HDFS user

$ hdfs dfsadmin -safemode get

If it confirms safe mode then it's a good idea to save the namespace first

$ hdfs dfsadmin -saveNamespace

Now leave safe mode

$ hdfs dfsadmin -safemode leave

Now you ATS should start without any problem

[#3]

dear Shelton

so each time we restart all required services from ambari ,

and in case timeline service failed , then need to check if HDFS in safe mode and if its true then leave safe mode

let me know if this is the procedure that we need to do when timeline service failed?