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https://issues.apache.org/jira/browse/LENS-619?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14598879#comment-14598879
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Jaideep Dhok commented on LENS-619:
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Hi [~himanshu.gahlaut] Can you put up a design proposal? Also, we need to break
this into subtasks.
I agree with Amareshwari that policy should be pluggable.
Regarding the proposal -
# Is the 'wait queue' persisted across restarts? Is it bounded?
# All N queries for a user may have different resource requirements. Rather
than limiting the 'number' of queries we should limit based on the resources
consumed by a user across different drivers. One option is to use cumulative
query cost of running queries as a way to limit queries of a user. Since query
cost is supposed to give a hint about resource usage of the query, it can be
used here.
# Is it N queries across all drivers? or N per driver
> Applying Query Running Constraint before allowing a query to run
> ----------------------------------------------------------------
>
> 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 priority
> queue for processing.
> Next candidate query picked up from priority 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 priority queue to be re-processed.
> [Initial thought]: 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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