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From "Guangya Liu" <gyliu...@gmail.com>
Subject Re: Review Request 35702: Added /reserve HTTP endpoint to the master.
Date Sun, 06 Sep 2015 03:31:20 GMT

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https://reviews.apache.org/r/35702/#review97881
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Ship it!


Ship It!

- Guangya Liu


On 九月 4, 2015, 11:19 p.m., Michael Park wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/35702/
> -----------------------------------------------------------
> 
> (Updated 九月 4, 2015, 11:19 p.m.)
> 
> 
> Review request for mesos, Adam B, Benjamin Hindman, Ben Mahler, Jie Yu, Joris Van Remoortere,
and Vinod Kone.
> 
> 
> Bugs: MESOS-2600
>     https://issues.apache.org/jira/browse/MESOS-2600
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> This involved a lot more challenges than I anticipated, I've captured the various approaches
and limitations and deal-breakers of those approaches here: [Master Endpoint Implementation
Challenges](https://docs.google.com/document/d/1cwVz4aKiCYP9Y4MOwHYZkyaiuEv7fArCye-vPvB2lAI/edit#)
> 
> Key points:
> 
> * This is a stop-gap solution until we shift the offer creation/management logic from
the master to the allocator.
> * `updateAvailable` and `updateSlave` are kept separate because
>   (1) `updateAvailable` is allowed to fail whereas `updateSlave` must not.
>   (2) `updateAvailable` returns a `Future` whereas `updateSlave` does not.
>   (3) `updateAvailable` never leaves the allocator in an over-allocated state and must
not, whereas `updateSlave` does, and can.
> * The algorithm:
>     * Initially, the master pessimistically assume that what seems like "available" resources
will be gone.
>       This is due to the race between the allocator scheduling an `allocate` call to
itself vs master's
>       `allocator->updateAvailable` invocation.
>       As such, we first try to satisfy the request only with the offered resources.
>     * We greedily rescind one offer at a time until we've rescinded sufficiently many
offers.
>       IMPORTANT: We perform `recoverResources(..., Filters())` which has a default `refuse_sec`
of 5 seconds,
>       rather than `recoverResources(..., None())` so that we can virtually always win
the race against `allocate`.
>       In the rare case that we do lose, no disaster occurs. We simply fail to satisfy
the request.
>     * If we still don't have enough resources after resciding all offers, be semi-optimistic
and forward the
>       request to the allocator since there may be available resources to satisfy the
request.
>     * If the allocator returns a failure, report the error to the user with `Conflict`.
> 
> This approach is clearly not ideal, since we would prefer to rescind as little offers
as possible.
> 
> 
> Diffs
> -----
> 
>   src/master/http.cpp 94e97a2898106579434e8cdec04b7b0e130a810e 
>   src/master/master.hpp e1331851c19e3372a4a525dcfd7ba2a01c3e97a6 
>   src/master/master.cpp 5589eca4317b597de509f3387cfc349083b361ac 
>   src/master/validation.hpp 43b8d84556e7f0a891dddf6185bbce7ca50b360a 
>   src/master/validation.cpp ffb7bf07b8a40d6e14f922eabcf46045462498b5 
> 
> Diff: https://reviews.apache.org/r/35702/diff/
> 
> 
> Testing
> -------
> 
> `make check`
> 
> 
> Thanks,
> 
> Michael Park
> 
>


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