> On Feb. 19, 2016, 6:32 a.m., Adam B wrote:
> > include/mesos/mesos.proto, line 1600
> > <https://reviews.apache.org/r/43616/diff/2/?file=1252884#file1252884line1600>
> >
> >     Is it ok for labels to contain duplicate keys even if the values are 
> > different?
> >     That sounds like undefined behavior too. Is the label-consumer supposed 
> > to use all values, first value, last value?

To me, the issue isn't how the label-consumer is supposed to interpret the 
labels: rather, labels with duplicate key-value pairs are not handled correctly 
by Mesos (our equality operator is wrong for this situation -- see MESOS-4445). 
The initial feeling was that the runtime cost of fixing the equality operator 
wasn't worth it (although based on the experiments in 
https://reviews.apache.org/r/43686/, it is unclear whether this is true).

The equality operator behaves correctly for labels with duplicate keys but 
distinct values associated with those keys. How label consumers are supposed to 
interpret them is up to the application.


> On Feb. 19, 2016, 6:32 a.m., Adam B wrote:
> > include/mesos/mesos.proto, line 1634
> > <https://reviews.apache.org/r/43616/diff/2/?file=1252884#file1252884line1634>
> >
> >     Are you intentionally leaving out the Labels field in DiscoveryInfo, 
> > Port, NetworkInfo, Image.Appc? I didn't think Mesos interpreted any of 
> > these either.

It just seemed a bit verbose to copy the same comment that many times, so I 
settled for documenting the most common use-sites as well as the definition of 
`Labels`. Happy to change that if people would rather see it done another way 
though.


- Neil


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On Feb. 17, 2016, 6:44 p.m., Neil Conway wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/43616/
> -----------------------------------------------------------
> 
> (Updated Feb. 17, 2016, 6:44 p.m.)
> 
> 
> Review request for mesos and Michael Park.
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> The implementation of the equality operator for `Labels` is buggy for labels
> that contain duplicates. We might want to revisit fixing the implementation of
> that operator (which might be expensive; MESOS-4445), but in the short-term we
> should document that duplicates should not be specified.
> 
> 
> Diffs
> -----
> 
>   include/mesos/mesos.proto e24d3e03a7dc7c6bfd07f34531cb593fe4925646 
>   include/mesos/v1/mesos.proto d909e60ddfd8e3ba2075f82c372edde04cd99d54 
> 
> Diff: https://reviews.apache.org/r/43616/diff/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> Neil Conway
> 
>

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