Prasanth Jayachandran created TEZ-3078:
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             Summary: Provide a mechanism for AM to let Client know about the 
reason for failure
                 Key: TEZ-3078
                 URL: https://issues.apache.org/jira/browse/TEZ-3078
             Project: Apache Tez
          Issue Type: Improvement
    Affects Versions: 0.8.3
            Reporter: Prasanth Jayachandran


When working on HIVE-12959 for LLAP, the requirement is when we submit a query 
to LLAP task scheduler and if there are no LLAP daemons we should fail the 
query instead of waiting indefinitely for daemons to show up. For this to work, 
the task scheduler has to provide a mechanism to let the AM know that the 
scheduler service cannot proceed further as there are no daemons running. 
Currently there is no way for the task scheduler to let AM know about this 
information. The only way right now is to send back exception using 
TaskSchedulerContext.onError() API. This will kill the AM but AM will restart 
to recover the DAG. It will be better if there a way to let AM know about 
daemon status via some status response based on which AM should avoid 
restarting. It will be even better if we can provide a way for AM to 
communicate this information back to the client (hive CLI or HiveServer2).



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