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https://issues.apache.org/jira/browse/YARN-6451?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15994014#comment-15994014
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Carlo Curino commented on YARN-6451:
------------------------------------

I see two or three alternatives:
 # Hard-coding the most important invariants in a programmatic way, you see an 
example of this in: YARN-6473, where I poke the {{ReservationSystem}} and 
{{YarnScheduler}} to check whether their data-structures remain in sync during 
execution. This is more minimalistic/efficient, but any extension requires code 
changes. For example, you can maintain an observer of container allocations, 
and check that certain ordering properties are respected.
 # Expand the mechanics of YARN-6451 by adding "bindings" for many more parts 
of the RM internal state, which one is allowed to mentioned in the 
{{invariants.txt}} file. Metrics was a natural starting point, as the cost of 
gathering is already there, and their names are externally known. To minimize 
the cost, we could load the {{invariants.txt}} expressions, and then limit the 
"state" we probe to be the least one covering the needs of our expressions.
 # Leverage compiler APIs / aspects / dependency-injection type of tricks to 
dynamically modify the code that does the binding work, to cover whatever 
appears in {{invariants.txt}} file. This is obviously the richest one, though 
it has some maintainability issues. 

In YARN-6547 I propose a simple way of combining YARN-6363 and YARN-6451 
capabilities to run tests that check an SLS run for common invariants (both 
during and at the end of the run). That is mostly a mechanism patch, but we can 
work together to define very tight yet robust invariants for specific runs.


> Add RM monitor validating metrics invariants
> --------------------------------------------
>
>                 Key: YARN-6451
>                 URL: https://issues.apache.org/jira/browse/YARN-6451
>             Project: Hadoop YARN
>          Issue Type: New Feature
>            Reporter: Carlo Curino
>            Assignee: Carlo Curino
>             Fix For: 3.0.0-alpha3
>
>         Attachments: YARN-6451.v0.patch, YARN-6451.v1.patch, 
> YARN-6451.v2.patch, YARN-6451.v3.patch, YARN-6451.v4.patch, YARN-6451.v5.patch
>
>
> For SLS runs, as well as for live test clusters (and maybe prod), it would be 
> useful to have a mechanism to continuously check whether core invariants of 
> the RM/Scheduler are respected (e.g., no priority inversions, fairness mostly 
> respected, certain latencies within expected range, etc..)



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