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Directing output of out external threads/processes to specific cells

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
20/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
cpp, linux, python

Research direction

Review ipykernel PR #1186 first to understand the existing routing for Python threads and asyncio tasks. No source file or test is named; the issue needs an agreed design for external thread/process output, followed by implementation and tests that demonstrate output reaches the intended cell.

Written by the indexing model from the issue text.

Description

https://github.com/ipython/ipykernel/pull/1186 made output of Python threads and asyncio tasks go to right cells. It would be interesting, although challenging to make it work for any thread/process (e.g. created from a C++ dependency).

Here are two possible options to consider:

  • (a) define format (e.g. JSON-RPC) where each write to the stdio/stderr would be a packed with both target cell ID and a blob message (slight challenges related to buffering and format choice) - this is how LSP works.
  • (b) allow to open file descriptors per-cell (*2 for stdout/stderr) and make their IDs easily accessible to the external processes for writing (this could use virtual filesystem on Linux), either by having an API return the file descriptor or by having them in predictable locations (e.g. relative to kernel runtime); of course the challenges here would be around OS-specific limits for watching files and the allowed number of open file descriptors.

Any thoughts on whether any of these would be in scope?

Dominant language
Python
Stars
734
Forks
411
Avg merge
1d 2h
Merged PRs (30d)
9

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