Performance Improvements using Worker Threads

[DonJayamanne]

I've been looking into a performance issue related to opening notebook.
TLDR - Opening a notebook in widows for Chris Dias and me takes 20-30 seconds (Jupyter extension is not doing anything).
If we disable the Python extension, it opens almost immediately (~5 seconds).

I think the delay is in Python extension spawning n processes. I know we're making changes to environment discovery.
However I think we can improve this even further (or, even with the current changes, it might not be sufficient).

I believe the problem lies with the spawning of processes, if we spawn proceses, it takes a few ms to just spawn the process, e.g. i know on Windows, spawning a conda process takes a few seconds, & that's blocking (spawning processes in node is synchronous) - but communication is async.

This blocks the main thread, hence blocks all other extensions (kinda explains why it takes so many seconds to just open a notebook when Jupyter isn't doing anything).

Suggestion - Why not spawn the processes in a worker thread (completely non-blocking)
I did look into this last year, & we can do this today.

What can we move to these worker threads:
Spawning processes just to get their environment information
Spawning processes to run code e.g. python -c "import ipykernel"
& other simple processes

[karthiknadig]

@DonJayamanne we should turn this into a meta issue an create work items for each particular case we move into worker. This is great if we can do this where ever possible.

[DonJayamanne]

FYI - We have managed to resolve the performance issue in Jupyter notebooks by delaying the loading of the Python extension. Now Jupyter Notebooks open in around 3 seconds, basically the Python extension gets loaded/activated AFTER the notebook is opened.
Hence this isn't a priority anymore, but if we had this, we'd ensure the Jupyter extension doesn't regress & we don't need to worry about other extensions blocking us. (or this extenison not blocking others)

[karrtikr]

• Spike: Investigate using webworker for Python discovery #21755