Run different worker types in separate threads

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
backend

Research direction

Start with the worker setup in temporalio/worker/_worker.py around lines 489-492, where workflow and activity workers currently share an event loop. Trace how worker types are created and coordinated, including the future Nexus workers mentioned in the issue. Done means workflow, activity, and eventually Nexus workers can run in separate threads without blocking one another.

Written by the indexing model from the issue text.

Description

enhancement

Currently, when workflow and activity workers are run in the same process, they share the the same thread (same event loop):

https://github.com/temporalio/sdk-python/blob/b0dfaef0f029244a44f56c4c1970cda8621b4e68/temporalio/worker/_worker.py#L489-L492

Running these (and Nexus workers when they arrive) in different threads would prevent an async activity that incorrectly does blocking I/O from blocking workflow progress. In addition to limiting blast radius it should make it easier to understand the failure modes.

Dominant language
Python
Stars
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Forks
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Avg merge
3d 2h
Merged PRs (30d)
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