ark: Cryptic warning after starting and interrupting Shiny application

[kevinushey]

Saw this in the console some time after a Shiny application was stopped:

Can't detect correct thread for auto_deleter_background.

It looks like this comes from httpuv; e.g.

https://github.com/rstudio/httpuv/blob/main/src/auto_deleter.h#L30

And the error seems to imply the destructor / deleter was run on a thread unrecognized by later.

For reference, the example code:

shiny::runExample("01_hello")

[kevinushey]

Putting this in private alpha in case this is indicative of a need to restructure how threads are oriented in ark.

[kevinushey]

Looks like this happens if the LSP thread runs some R code, and that triggers some finalizers registered via httpuv to run.

However, httpuv expects to either be on the "main" thread, or on its own background thread, as per:

https://github.com/rstudio/httpuv/blob/main/src/auto_deleter.h#L13-L51

https://github.com/rstudio/httpuv/blob/main/src/thread.cpp

[ryjohnson09]

I hit this same issue today. It's hard to replicate - but with enough runApp() calls followed by closing the app, I can usually get the message to appear.

Positron Version: 2023.09.0 (Universal) build 203
Code - OSS Version: 1.79.0
Commit: 519fbc7
Date: 2023-09-22T02:37:21.484Z
Electron: 22.3.10
Chromium: 108.0.5359.215
Node.js: 16.17.1
V8: 10.8.168.25-electron.0
OS: Darwin arm64 22.6.0

[lionel-]

Addressed by posit-dev/ark#109 and ready for review.

Should be fixed in builds >= 2023.10.0-1267.
Could you please confirm this is fixed @ryjohnson09?

[juliasilge]

I just tried running and interrupting Shiny apps many, many times in build 1269 and I never saw "Can't detect correct thread for auto_deleter_background." Working great for me. 👍

[ryjohnson09]

Addressed by posit-dev/amalthea#109 and ready for review.

Should be fixed in builds >= 2023.10.0-1267. Could you please confirm this is fixed @ryjohnson09?

Confirmed - thanks!!