[jira] [Comment Edited] (YARN-6451) Add RM monitor validating metrics invariants

["Carlo Curino (JIRA)" <ji...@apache.org>]

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

Carlo Curino edited comment on YARN-6451 at 5/2/17 11:31 PM:
-------------------------------------------------------------

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.
 # (discussing with [~chris.douglas] another option emerged) 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.



was (Author: curino):
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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