Reintroduce weight function

[jrbourbeau]

This PR adds the weight function (which was recently removed) back into distributed/worker.py. I heard this was being used by RAPIDS so it'd be good to keep it around for a bit before removing it in a future release.

cc @quasiben @kkraus14

[quasiben]

Thank you @jrbourbeau !

[pentschev]

Just FYI, we have no problem in moving to safe_sizeof, which is what we're doing in rapidsai/dask-cuda#584 . For the upcoming 0.19 release we're pinning Dask/Distributed 2021.04.0 in rapidsai/dask-cuda#585, which is something we had already decided to do some weeks back in RAPIDS. So if we're reintroducing this only because of dask-cuda that may not be necessary.

[jrbourbeau]

Thanks for the additional context @pentschev -- we're primarily adding this back for dask-cuda but, as the dask-cuda CI has pointed out, there could be other folks using weight too. Temporarily adding it back isn't a big deal from distributeds perspective.

Also, when is the 0.19 release due to be out? With dask / distributed being released this Friday, it may be beneficial to add weight back in to avoid any breakages between distributed 2021.04.1 and dask-cuda 0.19 being released

[pentschev]

Thanks for the additional context @pentschev -- we're primarily adding this back for dask-cuda but, as the dask-cuda CI has pointed out, there could be other folks using weight too. Temporarily adding it back isn't a big deal from distributeds perspective.

Makes sense to add the deprecation then.

Also, when is the 0.19 release due to be out? With dask / distributed being released this Friday, it may be beneficial to add weight back in to avoid any breakages between distributed 2021.04.1 and dask-cuda 0.19 being released

It's scheduled for release tomorrow, or Thursday depending on the timezone I guess, for reference we have a public RAPIDS Release Schedule. Parts of RAPIDS are already pinning Dask 2021.04.0 which is something we have decided to do some weeks ago anyway, so even if the release was after Friday I don't think it would impact us much, but thanks a lot for taking that into consideration, it's really appreciated! 😄