BUG FIX: Timeouts when launching 'cluster' and 'multisession' futures would produce an obscure error

Author: HenrikBengtsson

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: future
-Version: 1.80.0-9006
+Version: 1.80.0-9007
 Title: Unified Parallel and Distributed Processing in R for Everyone
 Depends:
     R (>= 3.2.0)

NEWS.md

@@ -12,6 +12,10 @@
 
 ## Bug Fixes
 
+ * When launching a 'cluster' or 'multisession' future timed out while
+   waiting for an available worker, it would produce an obscure
+   errorinstead of an informative timeout error.
+
  * Waiting for an available 'multicore', 'multisession', and 'cluster'
    worker with a timeout greater than 60 seconds could take much
    longer than that.

R/backend_api-11.ClusterFutureBackend-class.R

@@ -214,7 +214,7 @@ launchFuture.ClusterFutureBackend <- function(backend, future, ...) {
   ## rather than worker index? /HB 2025-07-04
   node_idx <- requestNode(await = function() {
     FutureRegistry(reg, action = "collect-first", earlySignal = TRUE, debug = debug)
-  }, backend = backend, timeout = timeout, delta = delta, alpha = alpha)
+  }, backend = backend, timeout = timeout, delta = delta, alpha = alpha, future = future)
   workers <- backend[["workers"]] ## Backend might have been updated
   future[["node"]] <- node_idx
 
@@ -1065,7 +1065,7 @@ requestNode <- local({
     if (inherits(con, "connection")) close(con)
   })
 
-  function(await, backend, timeout, delta, alpha, validateWorker = TRUE) {
+  function(await, backend, timeout, delta, alpha, validateWorker = TRUE, future = NULL) {
     debug <- isTRUE(getOption("future.debug"))
     if (debug) {
       mdebug_push("requestNode() ...")

inst/testme/test-requestNode.R

@@ -43,4 +43,20 @@ plan(sequential)
 
 message("*** requestNode() - timeout ... DONE")
 
+message("*** requestNode() - timeout when workers occupied ...")
+
+ovalue <- options(future.wait.timeout = 0.5)
+plan(cluster, workers = 1L)
+
+f1 <- future({ Sys.sleep(2); 42 })
+
+res <- tryCatch(future(1), error = identity)
+print(res)
+stopifnot(inherits(res, "FutureError"))
+
+plan(sequential)
+options(ovalue)
+
+message("*** requestNode() - timeout when workers occupied ... DONE")
+
 message("*** requestNode() ... DONE")