Publish Cython build

[mrocklin]

The Cython work seems mature enough that we might want to make it more publicly accessible with an optional separate package. Is this easy to do? I don't think that we should make it default yet, but having it be easy to install by people who are not familiar with Cython or compilation would probably be a plus.

One option would be to have a separate conda package conda install -c conda-forge distributed-cython (I'm curious how this would play with the dask metapackage). I wonder also if there is some more blessed way to specify variants.

cc @jakirkham

[jakirkham]

I don't think it is ready to live in a package yet. There are some other packaging related things we would want to sort out before doing that ( like PR #4326 ).

If you or your team need help building this, I'm happy to walk them through it. Assuming an environment with dask installed. Here are the steps:

1. Install the compilers and cython packages from conda-forge
2. Clone and cd into distributed/
3. Run python -m pip install -vv --no-deps --install-option="--with-cython=profile" . (drop =profile if not profiling)
4. Optionally verify scheduler is Cythonized: python -c "from distributed.scheduler import COMPILED; assert COMPILED"

[jakirkham]

@jrbourbeau and I made some improvement to testing in PR ( #4764 ). We did observe a few test failures (and are now skipped when the Scheduler is Cythonized). These are being tracked in PR ( #4767 ). Some of these issues may involve working with Cython to address

[jakirkham]

Now that nightlies are supported ( dask/community#76 ). Maybe a good first step would be to build nightlies with Cython enabled.

Admittedly this isn't quite as easy as installing from conda-forge, which we could also discuss, but it is an improvement from a user standpoint since they could install the package and would not need to compile from source.