Installing xarray-leaflet causes jupyter server to be really slow to start

[yuvipanda]

On a fresh install (no .pyc files), just importing xarray_leaflet takes about 9s:

(notebook) jovyan@jupyter-yuvipanda:~$ time python -c 'import xarray_leaflet'


real    0m9.275s
user    0m8.100s
sys     0m1.134s

As this is imported each time jupyter server is started, the user can not see their notebook until this initialization is complete. When coupled with other slow loading extensions (such as panel holoviz/panel#4271), this can cause server starts to time out in JupyterHubs. There is no way to disable this (jupyter server will still import your package even if it is disabled), so the only way to get a faster startup is to uninstall xarray-leaflet completely.

I think a majority of the import time comes from rioxarray

(notebook) jovyan@jupyter-yuvipanda:~$ time python -c 'import rioxarray'

real    0m7.707s
user    0m5.787s
sys     0m0.912s

[yuvipanda]

I opened jupyter-server/jupyter_server#1171 to make this information available more easily.

[davidbrochart]

Thanks for reporting the issue @yuvipanda.
Maybe we could implement something like lazy importing in xarray-leaflet?

[yuvipanda]

@davidbrochart yep that would seem to be the solution

[davidbrochart]

Actually xarray-leaflet doesn't import rioxarray. It depends on it and it uses properties of xarray's DataArray that exist because the array was opened with rioxarray, but that's external to xarray-leaflet.
Also, I don't think I can implement lazy importing anyway, since enabling xarray-leaflet only consists of importing it (it registers a DataArray accessor).
If rioxarray is the culprit, it might be worth opening an issue there? Although I'm not sure they can do a lot either, it's probably just the time to load GDAL in memory.

[yuvipanda]

sorry i misspoke, i meant https://github.com/xarray-contrib/xarray_leaflet/blob/main/xarray_leaflet/xarray_leaflet.py#L16 and rasterio as one of the culprits, not rioxarray. I think IPython is the other big culprit - moving those to be imported just before use might help?

[davidbrochart]

Actually there is not need to import LeafMap in __init__. One could e.g. import xarray_leaflet.map instead of import xarray_leaflet. That would be a breaking change though.

[yuvipanda]

@davidbrochart right, I'm not sure if a breaking change is desired - I don't know how far along the xarray-leaflet project is.

Another option is to split the serverextension into its own module perhaps? It could ship by default with xarray-leaflet, maybe even as part of the same package, but just be a different module?

[davidbrochart]

Another option is to split the serverextension into its own module perhaps?

Thanks, that's what I did in #80, and I released v0.2.2 with these changes.

[yuvipanda]

Thank you so much for your quick work on this, @davidbrochart!