> On Nov. 18, 2015, 4:05 p.m., Qian Zhang wrote:
> > src/master/http.cpp, line 2097
> > <https://reviews.apache.org/r/40244/diff/2/?file=1125056#file1125056line2097>
> >
> >     This comment may not be related to this patch. I am just curious, for ```required```, we have called ```flatten()``` to remove role from it when passing it into ```Master::Http::_operation()```. But here for ```offer->resources()```, we do not call ```flatten()``` to remove its role, so is it subtractable between ```required``` and ```offer->resources()```?
> 
> Michael Park wrote:
>     We `flatten` the resources for `/reserve` because the `required` represents the resources that we need in order to perform the reservation.
>     Suppose we want to end up with 2 reserved cpus. We `flatten` it, and search for 2 unreserved cpus in the received offers.
>     If we were to `flatten` the `offer.resources()` also, then an offer with 1 reserved cpu and 1 unreserved cpu would incorrectly satisfy our condition.
>     
>     In terms of subtractibility, that is determined on a per-resource basis, and non-subtractable resources are ignored.
>     For example, `[(2 unreserved cpus)] - [(1 reserved cpu), (1 unreserved cpu)]` == `[(1 unreserved cpu)]`.

Suppose ```offer.resources()``` is ```[(1 reserved cpu), (1 unreserved cpu)]```, and ```required``` is ```[(2 unreserved cpus)]```, so the result of ```required == required - offer.resources()``` is ```false```, that mean we will rescind this offer, right? But it may not make sense to me, because I think the **reserved** resource should not be rescinded.


- Qian


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On Nov. 18, 2015, 7:27 p.m., Neil Conway wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/40244/
> -----------------------------------------------------------
> 
> (Updated Nov. 18, 2015, 7:27 p.m.)
> 
> 
> Review request for mesos, Greg Mann and Michael Park.
> 
> 
> Bugs: MESOS-2455
>     https://issues.apache.org/jira/browse/MESOS-2455
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Clarified comments in Master::Http::_operation.
> 
> 
> Diffs
> -----
> 
>   src/master/http.cpp 1c4f1406f5d917f5d655a7d61d311365f8999ce0 
> 
> Diff: https://reviews.apache.org/r/40244/diff/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> Neil Conway
> 
>