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From Benjamin Mahler <bmah...@apache.org>
Subject Re: Review Request 70132: Do not implicitly decline speculatively converted resources.
Date Tue, 23 Apr 2019 16:37:31 GMT


> On April 23, 2019, 10:47 a.m., Benjamin Bannier wrote:
> > docs/scheduler-http-api.md
> > Line 132 (original), 132 (patched)
> > <https://reviews.apache.org/r/70132/diff/5/?file=2140649#file2140649line132>
> >
> >     What do you think of getting rid of "implicitly declined" behavior for "cancelling
operations"?
> >     
> >     It seems that behavior is more driven by the implementation than intuitive api
behavior; it e.g., forces frameworks to reason differently about operations executed in isolation
vs. executed together. It seems having the identical behavior for both cases would both be
easier to explain and also program against. The behavior that seems to make most sense for
me would be to only ever implictly decline "untouched resources", e.g., if accepting offered
`cpus:4` with `RESERVE(cpus:2, role) && UNRESERVE(cpus:2, role)` we would implicitly
decline only `cpus:2`.
> 
> Chun-Hung Hsiao wrote:
>     It seems to me that "cancelling operations" as something that are both 1. very rare
and 2. make little sense for frameworks, so I'm more like delivering a fix for common cases
without making the alrealy-messy code path more complicated. WDYT? Also @bmahler what's your
opinion on @bbannier's suggestion? IIRC you mentioned something like some are designed behaviors
before, but I didn't know the context.

Thanks for bringing this up, it's certainly a bit bizarre of a use case. I think the more
common case is UNRESERVE on its own, where it still seems a bit bizarre that the "untouched"
resources are declined with the filter and the UNRESERVE resources are not filtered. That
seems a bit arbitrary to me, but I'm not sure what to do about it without allowing the framework
to be explicit about which part it wants to "decline and filter" when accepting, and this
requires an interface change.

Personally I would consider RESERVE+UNRESERVE to be "touching" those resources, but I don't
think we should worry about it in this patch (I assume that wasn't your intent anyway, and
you were more wanting to raise this topic for discussion?)


> On April 23, 2019, 10:47 a.m., Benjamin Bannier wrote:
> > src/master/master.cpp
> > Lines 5963-5964 (original), 5983-5984 (patched)
> > <https://reviews.apache.org/r/70132/diff/5/?file=2140650#file2140650line5983>
> >
> >     Is this a workaround we need until MESOS-4553 gets resolved? If it is, let's
add a `TODO`.
> 
> Chun-Hung Hsiao wrote:
>     I don't know actually lol. I just copied it from https://github.com/apache/mesos/blob/45c9788618e7123f408a1dffcf6772a1285cd2e5/src/master/master.cpp#L10969-L10972,
as @mzhu suggested that if there's an allocation in between there might be offer fragmentation.
Is this a workaround for MESOS-4553?

Well, one could say all the interactions with the allocator around offers are a "workaround"
until MESOS-4553 is done :)

I would say that the pause/resume here is more a workaround of the limited recoverResources
interface (i.e. it doesn't let you specify a collection of resources and filters, so we need
to perform two calls). The only issue with pause/resume is: https://issues.apache.org/jira/browse/MESOS-9734


- Benjamin


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On April 23, 2019, 1:15 a.m., Chun-Hung Hsiao wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/70132/
> -----------------------------------------------------------
> 
> (Updated April 23, 2019, 1:15 a.m.)
> 
> 
> Review request for mesos, Benjamin Bannier, Benjamin Mahler, and Meng Zhu.
> 
> 
> Bugs: MESOS-9616
>     https://issues.apache.org/jira/browse/MESOS-9616
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Currently if a framework accepts an offer to perform pipelined
> operations, e.g., reserving resource, without a final consumer, the
> converted resources will be implicitly declined. This is an undesired
> behavior as the framework might want to reserve one resource first but
> launch a task later in the next allocation cycle. This patch fixes this
> behavior.
> 
> But, if the framework accepts an offers with multiple operations that
> cancel out each other, the resources consumed by these operations are
> still considered unused and will be declined.
> 
> 
> Diffs
> -----
> 
>   docs/scheduler-http-api.md a5327c229142267836f327f9c382ef50b7e334db 
>   src/master/master.cpp ad54ae217863a08f4e6d743b39c176b171353084 
>   src/tests/slave_tests.cpp b1c3a01031b917fb9773c8c890a8f88838870559 
> 
> 
> Diff: https://reviews.apache.org/r/70132/diff/5/
> 
> 
> Testing
> -------
> 
> make check
> 
> 
> Thanks,
> 
> Chun-Hung Hsiao
> 
>


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