Hi Kevin, Thanks for engaging with the community on this. My 2 cents:
1. I feel that this capabilities has a particular useful semantic which is lacking in the current reservation system: reserving some scarce resource for a* dynamic list of multiple roles:* Right now, any reservation (static or dynamic) can only express the semantic of "reserving this resource for the given role R". However, in a complex cluster, it is possible that we have [R1, R2, ..., RN] which wants to share the scarce resource among them but there is another set of roles which should never see the given resource. The new hierarchical role (and/or multi-role?) might be able to provide a better solution, but until that's widely available and adopted, the capabilities based hack is the only thing I know that can solve the problem. In fact, I think if we are going to wo with `--filter-gpu-resources` path, I think we should make the filter more powerful (i.e, able to handle all known framework <-> resource/host constraints and more types of scarce resources) instead of the piecewise patches on a specific use case. Happy to chat more on this topic. On Sat, May 20, 2017 at 6:45 PM, Kevin Klues <klue...@gmail.com> wrote: > Hello GPU users, > > We are currently considering deprecating the requirement that frameworks > register with the GPU _RESOURCES capability in order to receive offers that > contain GPUs. Going forward, we will recommend that users rely on Mesos's > builtin `reservation` mechanism to achieve similar results. > > Before deprecating it, we wanted to get a sense from the community if > anyone is currently relying on this capability and would like to see it > persist. If not, we will begin deprecating it in the next Mesos release and > completely remove it in Mesos 2.0. > > As background, the original motivation for this capability was to keep > “legacy” frameworks from inadvertently scheduling jobs that don’t require > GPUs on GPU capable machines and thus starving out other frameworks that > legitimately want to place GPU jobs on those machines. The assumption here > was that most machines in a cluster won't have GPUs installed on them, so > some mechanism was necessary to keep legacy frameworks from scheduling jobs > on those machines. In essence, it provided an implicit reservation of GPU > machines for "GPU aware" frameworks, bypassing the traditional > `reservation` mechanism already built into Mesos. > > In such a setup, legacy frameworks would be free to schedule jobs on > non-GPU machines, and "GPU aware" frameworks would be free to schedule GPU > jobs GPU machines and other types of jobs on other machines (or mix and > match them however they please). > > However, the problem comes when *all* machines in a cluster contain GPUs > (or even if most of the machines in a cluster container them). When this is > the case, we have the opposite problem we were trying to solve by > introducing the GPU_RESOURCES capability in the first place. We end up > starving out jobs from legacy frameworks that *don’t* require GPU resources > because there are not enough machines available that don’t have GPUs on > them to service those jobs. We've actually seen this problem manifest in > the wild at least once. > > An alternative to completely deprecating the GPU_RESOURCES flag would be to > add a new flag to the mesos master called `--filter-gpu-resources`. When > set to `true`, this flag will cause the mesos master to continue to > function as it does today. That is, it would filter offers containing GPU > resources and only send them to frameworks that opt into the GPU_RESOURCES > framework capability. When set to `false`, this flag would cause the master > to *not* filter offers containing GPU resources, and indiscriminately send > them to all frameworks whether they set the GPU_RESOURCES capability or > not. > > , this flag would allow them to keep relying on it without disruption. > > We'd prefer to deprecate the capability completely, but would consider > adding this flag if people are currently relying on the GPU_RESOURCES > capability and would like to see it persist > > We welcome any feedback you have. > > Kevin + Ben > -- Cheers, Zhitao Li
