Add dask proxy to labextension.yaml

[lsterzinger]

It'd be nice if the pangeo notebook dask-labextension knew to use the /proxy/localhost:8787 option by default, since as @scottyhq mentioned in Gitter it's probably more common to be running a LocalCluster rather than a GatewayCluster.

Right now, I'm able to append:

distributed:
  dashboard:
    link: "/proxy/localhost:8787"

To ~/.config/dask/labextension.yaml view the line:

RUN echo 'distributed:\n  dashboard:\n    link: "/proxy/localhost:8787"' >> /home/jovyan/.config/dask/distributed.yaml

in my Dockerfile, and confirmed it worked in pangeo binder. I can open a PR to add this to one of Pangeo dockerfiles, but I'm not sure which one. base-image?

[scottyhq]

Thanks @lsterzinger , let's wait on a pull request because i think there might be a few approaches.

Ideally, the reported dashboard url would be functional for both a LocalCluster and GatewayCluster. So instead of overriding the global dashboard config link, we'd only want to do this for LocalClusters. @TomAugspurger seems Dashboard: http://127.0.0.1:8787/status is also reported for LocalClusters on the Planetary Computer hub, do you have a recommended way to change that to /proxy/localhost:8787?

[scottyhq]

@consideRatio @ian-r-rose there seem to be a lot of related issues discussed over in the dask-labextension repository (e.g. dask/dask-labextension#41) but i'm not tacking down a relevant per-cluster config for the dashboard URL ?

[TomAugspurger]

It seems to me like setting distributed.dashboard.link to "/user/{JUPYTERHUB_USER}/proxy/{port}/status" does the trick, for both LocalCluster and dask Gateway based clusters.

So maybe it's OK to just change that setting? I'm not sure how the dask-gateway URL is determined, but it doesn't seem to be harmed by setting it.

[lsterzinger]

Is setting that parameter from within the notebook the same as writing to the config file like I did during the docker image build stage?

[TomAugspurger]

Setting it in the notebook was just for illustration, but yes, it's equivalent.

IMO, this shouldn't be set here in pangeo-docker-images. I think it should be set wherever the image is being used (e.g. https://github.com/pangeo-data/pangeo-cloud-federation)