I am working with a function that starts with parallel::makeCluster() and ends with parallel::stopCluster(). Sometimes it crashes in the middle and does not stop the cluster.

Demonstration code:

library('doParallel')

show_problem <- function(n.cores=7) {
  clust <- makeCluster(n.cores,type='FORK')
  registerDoParallel(cl = clust)
  stop('Here is an error message, the function will stop before it gets to the next line.')
  parallel::stopCluster(cl = clust)
}

show_problem()
showConnections(all=T)

After the function crashes, showConnections(all=T) will show its “sockconn” connections for workers are still open, and the threads for the workers will still be running. But I can’t call stopCluster() because the object “clust” only exists within the scope of the show_problem() function and that function has ended.

Is there some way for me to find whatever entity “clust” was referring to from outside the function, so I can still run stopCluster() ?