Changing options `warn` causes infinite waiting on a multisession in RStudio Rmd

[VasLem]

That is a really cryptic issue, and I am not sure whether it has to do with globals being set.

Reproduce example
The following infinitely waits in RStudio (in WSL2) but runs OK in an R terminal:

op <- options(warn = 2)$warn
future::plan(future::multisession, workers = 2)
future.apply::future_lapply(
    X=seq(10),
    FUN=function(x){
        print(x)
    }
)

Session information

R version 4.3.3 (2024-02-29)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 24.04.2 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3 
LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.26.so;  LAPACK version 3.12.0

locale:
 [1] LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8        LC_COLLATE=C.UTF-8     LC_MONETARY=C.UTF-8   
 [6] LC_MESSAGES=C.UTF-8    LC_PAPER=C.UTF-8       LC_NAME=C              LC_ADDRESS=C           LC_TELEPHONE=C        
[11] LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C   

time zone: Europe/Brussels
tzcode source: system (glibc)

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
 [1] compiler_4.3.3      parallelly_1.45.1   parallel_4.3.3      tools_4.3.3         rstudioapi_0.17.1   future.apply_1.20.0
 [7] listenv_0.9.1       codetools_0.2-19    digest_0.6.37       globals_0.18.0      future_1.67.0     

[HenrikBengtsson]

That's weird. What version of RStudio do you run?

I don't have easy access to WSL, so it's hard for me to troubleshoot there. FWIW, I tried on Ubuntu 24.04 with RStudio 2025.09.0 with R 4.4.3 as well as R 4.5.1 and with all R packages up-to-date, but that did not stall. It worked as expected.

Does it also stall if you use one of the following

1. future::plan(future::sequential)
2. future::plan(future.callr::callr, workers = 2)
3. future::plan(future.mirai::mirai_multisession, workers = 2)

? Testing those can help us narrow in on what you're experiencing.

Also, if you enable debugging by

options(future.debug = TRUE)

what are the last 20-30 lines of debug output you get? That should tell us where it stalls.

[VasLem]

Hi @HenrikBengtsson , apologies for the late reply. I was not able to reproduce it when I restart Windows. In general though, I see a lot of stalls with the package, that are not even resolved when I restart wsl, I have to reboot my entire machine to make things run back normal, which can become very frustrating in the long run. Could it be that tmp files are used as pipes, that are never consumed appropriately? I will try to have the debug option set next time this problem occurs.