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https://issues.apache.org/jira/browse/LENS-619?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Himanshu Gahlaut updated LENS-619:
----------------------------------
    Summary: Applying Query Launching Constraints before allowing a query to be 
launched  (was: Applying Query Running Constraint before allowing a query to 
run)

> Applying Query Launching Constraints before allowing a query to be launched
> ---------------------------------------------------------------------------
>
>                 Key: LENS-619
>                 URL: https://issues.apache.org/jira/browse/LENS-619
>             Project: Apache Lens
>          Issue Type: New Feature
>            Reporter: Himanshu Gahlaut
>            Assignee: Himanshu Gahlaut
>
> [June 23. 2015]: 
> This is the refined model after knowledge crunching:
> Lens will always accept a new query from a user and put it in a scheduling 
> queue for processing.
> Next candidate query picked up from scheduling queue for processing will be 
> run only if a query running constraint evaluated on running queries and 
> candidate query allows the candidate query to be run, otherwise the candidate 
> query will be moved to waiting queries list.
> When any running query is finished, result of evaluation of query constraint 
> might change, waiting queries might become eligible to be run, hence waiting 
> queries will be moved back to scheduling queue to be re-processed.
> Waiting Queries will be persisted across server restarts.
> [Initial thought] (Not in work): Fair Usage Policy for using Lens
> After a user has used the lens system beyond fair usage policy, he will get 
> lens features in degraded mode. 
> One of the forms of fair usage policy could be that at any point in time only 
> N queries can be present in RUNNING state for a user. 
> If N queries of a user are in RUNNING state, then a new query submitted by 
> same user will stay in QUEUED state until one of the N queries in RUNNING 
> state have moved to SUCCESSFUL, FAILED, OR CANCELLED state.



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