Feature Request: Option to disable debugging for specific threads

[Qasemt]

Feature Request: Option to disable debugging for specific threads

Description

Currently, debugpy does not provide an option to disable debugging for specific threads. This becomes challenging in multi-threaded applications where certain threads need to run without interruptions caused by breakpoints or debugging overhead.

Proposed Solution

Introduce an API or configuration option (e.g., disable_debug_for_thread(thread_id) or a similar mechanism) to exclude specific threads from being debugged.

Use Case

In a multi-threaded application, developers might want to focus debugging only on specific threads while allowing others to execute uninterrupted. This feature would improve debugging efficiency in complex scenarios.

Additional Notes

• A similar feature exists in some other debugging tools, and it greatly enhances usability in multi-threaded applications.
• If possible, allow thread-specific logging as an additional option.

 
import threading
import sys

def thread_function():
    # Simulate disabling debugging for this thread
    sys.settrace(None)  # This disables debugging for the current thread

    # Simulate work
    for i in range(5):
        print(f"Thread running iteration {i}")
        import time
        time.sleep(1)

[eleanorjboyd]

Hi! This would be required on the debugpy level and not something we can just implement on the surface, sending it there. Thanks!

[rchiodo]

I think this might be possible, but it can get very complicated. See this issue here for some of why:
#1475

[rchiodo]

Converting to a discussion item for up votes

[rchiodo]

You can eliminate debugger overhead (especially in 3.12 and later) with specific rules in your launch.json:

    {
      "name": "Python: Current File",
      "type": "python",
      "request": "launch",
      "program": "${file}",
      "console": "integratedTerminal",
      "rules": [
          {"path": "<glob pattern>", "include": true},  // Include or Exclude using a glob pattern or file name (include: false is how you exclude)
          {"module": "module name", "include": true}, // Include or Exclude by module name
        ],
    },

This won't stop threads from being suspended during a breakpoint but it will eliminate any tracing code running in certain modules or files.

[victorallume]

When I specify an include rule for just the file I want to debug, it works (i.e. the breakpoint stays in that file). But I'd rather set up an exclude rule than to have to set up include rules for every other file.

[rchiodo]

'exclude' isn't allowed. You use 'include': false to indicate excluded.

I just tried it with this:

    {
      "name": "Python Debugger: Current File",
      "type": "debugpy",
      "request": "launch",
      "program": "${file}",
      "console": "integratedTerminal",
      "rules": 
        [
          {"path": "C:\\Users\\rchiodo\\source\\testing\\test_pylance\\excluded_by_debug_rules.py", "include": false},  // Include or Exclude using a glob pattern or file name
        ],
    },

And it doesn't hit breakpoints in the excluded_by_debug_rules.py.

If it's picking the wrong thread when hitting a breakpoint, that sounds like a bug I recently fixed. What's your debugpy version?

[victorallume]

OK, thanks, using "include": false works. The original instructions didn't make this clear.

I'm using the following debugpy (as per the extension info in vscode)
Identifier ms-python.debugpy
Version 2024.14.0
Last Updated 2025-01-15, 15:06:35

[rchiodo]

This issue here:
#1765

Which is fixed in the preview version of the ms-python.debugpy extension (version 2024.15.202501280) and debugpy 1.8.12

[victorallume]

If it's picking the wrong thread when hitting a breakpoint, that sounds like a bug I recently fixed. What's your debugpy version?

I've just switched to the pre-release (2024.15.2025012801) and removed my launch.json changes, and it stays in the right thread.

Thanks for your help.