khogeland commented on issue #26687: [SPARK-30055][k8s] Allow configuration of 
restart policy for Kubernetes pods
URL: https://github.com/apache/spark/pull/26687#issuecomment-568070160
 
 
   > Particularly, if it gets set to Always, what's the implication of that for 
batch run-to-completion jobs?
   
   I think this is a documentation concern, because it's strongly recommended 
you don't use kubelet restart with batch mode (due to lingering executors after 
driver completion). At least, if you're trying to execute at-most-once, you 
can't guarantee the deletion of the executor when the driver completes.
   
   >Further, I'm not 100% sure how kubelet sets the state of an executor pod if 
the executor container completes in between restarts
   
   The pod phase stays as "Running", it's only the container status that is 
updated (which Spark doesn't use). The operator will need to be updated to 
support that, which I have the code for, I've just been waiting until I know 
how this PR will end up.
   
   >Even for streaming jobs that need to continuously run, is it simply a 
matter of restarting the executor pods that inherit the same executor IDs?
   
   It looks like no backends currently recycle executor IDs, so I'm going to 
investigate if it's possible to avoid any issues by having the executors 
generate their own IDs during startup on k8s.
   
   >It would be up to the user to know how to use the restart policy in a 
manner that doesn't cause unwanted behavior.
   
   Agreed, I'll need to add some documentation here. The driver restart policy 
is self-explanatory, but the executor restart has subtleties that need 
explanation.

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