WISH: Muffle warning on 'In mccollect(jobs = jobs, wait = TRUE) : # 1 parallel job did not deliver a result' when multicore worker crashes

[HenrikBengtsson]

If a forked child process crashes/terminates, calling result() on the corresponding multicore future, directly or indirectly, will trigger a warning that comes from the parallel package:

library(future)
plan(multicore, workers = 2L)
f <- future(quit("no"))
r <- tryCatch(result(f), error = identity)
# Warning message:
# In mccollect(jobs = jobs, wait = TRUE) :
#   1 parallel job did not deliver a result
print(r)
# <FutureError: Failed to retrieve the result of MulticoreFuture (<none>) from the
# forked worker (on localhost; PID 21926). Post-mortem diagnostic: No process 
# exists with this PID, i.e. the forked localhost worker is no longer alive.>

Action

Have result() for MulticoreFuture muffle this warning.

[HenrikBengtsson]

While thinking about it, unless we capture and relay the information in this warning, maybe it's better to let the warning stay? It'll add information when it comes to troubleshooting - and then warning only occurs when there's a serious problem so it's a rare event.