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From "Craig Welch (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3318) Create Initial OrderingPolicy Framework and FifoOrderingPolicy
Date Mon, 13 Apr 2015 16:42:13 GMT

    [ https://issues.apache.org/jira/browse/YARN-3318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14492615#comment-14492615
] 

Craig Welch commented on YARN-3318:
-----------------------------------

Looking again at using ResourceUsage instead of the initial use of application demand and
consumption, while it may be preferable for future cases like queues with node label aware
policies, there are deficiencies which need to be addressed to use it for the initial case,
and it makes it more complex to do so.  In fact, for the initial case, this approach is inferior.

ResourceUsage is still a bit rough and incomplete, get does not properly handle the ANY/ALL
case, which is what we need for application fairness - otherwise, applications whose resource
requests are labeled something other than NO_LABEL will be erroneously preferred for scheduling
in the fair case.  The prior approach was working with full consumption and demand and did
not have this issue and did not require additional change to support fairness properly.

Even supporting ANY/ALL in ResourceUsage is a little tricky, as I see no reason why someone
could not set values on ResourceUsage using the ANY label definition, and then there is a
question as to what is the proper behavior for an ANY get request - should it sum all the
values for all labels (which is, in some sense, correct), or just return the previously set
ANY value? Should we disallow setting ANY? (that seems a bit arbitrary...) My suggestion is
that we introduce explicit getAll(Used, Pending, etc), (not an ALL CommonNodeLabelsManager
constant, I think this just moves/replicates the existing problem).  There would be no corresponding
setAll.  getAll(XYZ) would iterate all labels in ResourceUsage for the passed ResourceType
and return a total.

For OrderingPolicy, the values should be cached on ResourceUsage instead of in SchedulableEntity
for cases where that is needed - cloning an entire ResourceUsage will be expensive, inefficient,
and unnecessary.  We could add a separate cache collection in ResourceUsage, but I think it
would actually be better to add values to the ResourceType enum, SCHEDULING_USED, SCHEDULING_PENDING

When updating the cached value for Used, OrderingPolicy would then call getAllUsed() on ResourceUsage
and set the resulting value with set (ANY node label expression, SCHEDULING_USED ResourceType),
and for demand, getAllPending() and then set ANY node label expression, SCHEDULING_PENDING

When getting the cached value, OrderingPolicy would call getUsed(ANY nlexpression, SCHEDULING_USED
ResourceType) and for pending, getPending(ANY, SCHEDULING_PENDING)

I'm inclined to roll forward with using ResourceUsage despite this additional scope to ease
future usecases, but we need to be very careful about continuing to pull in additional change
and complexity which is not required right now, and should avoid doing so again this iteration.
 It's good to aim for a stable api, but it's also good to complete the initial functionality,
and to realize it's not possible to anticipate all future needs / highly likely there will
be some change to api's like this as the system evolves.

> Create Initial OrderingPolicy Framework and FifoOrderingPolicy
> --------------------------------------------------------------
>
>                 Key: YARN-3318
>                 URL: https://issues.apache.org/jira/browse/YARN-3318
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: scheduler
>            Reporter: Craig Welch
>            Assignee: Craig Welch
>         Attachments: YARN-3318.13.patch, YARN-3318.14.patch, YARN-3318.17.patch, YARN-3318.34.patch,
YARN-3318.35.patch, YARN-3318.36.patch, YARN-3318.39.patch, YARN-3318.45.patch, YARN-3318.47.patch,
YARN-3318.48.patch, YARN-3318.52.patch, YARN-3318.53.patch, YARN-3318.56.patch
>
>
> Create the initial framework required for using OrderingPolicies and an initial FifoOrderingPolicy



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