backport of commit dd396a3 (#24520)

Co-authored-by: Seth Hoenig <[email protected]>

.changelog/24494.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+windows: Restore process accounting logic from Nomad 1.6.x
+```

drivers/shared/executor/procstats/list_test.go

@@ -63,31 +63,26 @@ func Test_list(t *testing.T) {
 		name     string
 		needles  int
 		haystack int
-		expect   int
 	}{
 		{
 			name:     "minimal",
 			needles:  2,
 			haystack: 10,
-			expect:   16,
 		},
 		{
 			name:     "small needles small haystack",
 			needles:  5,
 			haystack: 200,
-			expect:   212,
 		},
 		{
 			name:     "small needles large haystack",
 			needles:  10,
 			haystack: 1000,
-			expect:   1022,
 		},
 		{
 			name:     "moderate needles giant haystack",
 			needles:  20,
 			haystack: 2000,
-			expect:   2042,
 		},
 	}
 
@@ -100,11 +95,10 @@ func Test_list(t *testing.T) {
 				return procs, nil
 			}
 
-			result, examined := list(executorPID, lister)
+			result := list(executorPID, lister)
 			must.SliceContainsAll(t, expect, result.Slice(),
 				must.Sprintf("exp: %v; got: %v", expect, result),
 			)
-			must.Eq(t, tc.expect, examined)
 		})
 	}
 }

drivers/shared/executor/procstats/list_windows.go

@@ -26,6 +26,6 @@ import (
 // happens when you use syscalls to work your way from the root down to its
 // descendants.
 func List(executorPID int) set.Collection[ProcessID] {
-	procs, _ := list(executorPID, ps.Processes)
+	procs := list(executorPID, ps.Processes)
 	return procs
 }

drivers/shared/executor/procstats/procstats.go

@@ -82,51 +82,40 @@ func Aggregate(systemStats *cpustats.Tracker, procStats ProcUsages) *drivers.Tas
 	}
 }
 
-func list(executorPID int, processes func() ([]ps.Process, error)) (set.Collection[ProcessID], int) {
-	family := set.From([]int{executorPID})
+func list(executorPID int, processes func() ([]ps.Process, error)) set.Collection[ProcessID] {
+	processFamily := set.From([]ProcessID{executorPID})
 
-	all, err := processes()
+	allPids, err := processes()
 	if err != nil {
-		return family, 0
+		return processFamily
 	}
 
-	parents, examined := mapping(all)
-	examined += gather(family, parents, executorPID)
-
-	return family, examined
-}
-
-func gather(family set.Collection[int], parents map[int]set.Collection[int], parent int) int {
-	examined := 0
-	candidates, ok := parents[parent]
-	if !ok {
-		return examined
-	}
-	for _, candidate := range candidates.Slice() {
-		examined++
-		family.Insert(candidate)
-		examined += gather(family, parents, candidate)
+	// A mapping of pids to their parent pids. It is used to build the process
+	// tree of the executing task
+	pidsRemaining := make(map[int]int, len(allPids))
+	for _, pid := range allPids {
+		pidsRemaining[pid.Pid()] = pid.PPid()
 	}
 
-	return examined
-}
-
-// mapping builds a reverse map of parent to children
-func mapping(all []ps.Process) (map[int]set.Collection[int], int) {
+	for {
+		// flag to indicate if we have found a match
+		foundNewPid := false
 
-	parents := map[int]set.Collection[int]{}
-	examined := 0
+		for pid, ppid := range pidsRemaining {
+			childPid := processFamily.Contains(ppid)
 
-	for _, candidate := range all {
-		if candidate != nil {
-			examined++
-			if children, ok := parents[candidate.PPid()]; ok {
-				children.Insert(candidate.Pid())
-			} else {
-				parents[candidate.PPid()] = set.From([]int{candidate.Pid()})
+			// checking if the pid is a child of any of the parents
+			if childPid {
+				processFamily.Insert(pid)
+				delete(pidsRemaining, pid)
+				foundNewPid = true
 			}
 		}
+
+		if !foundNewPid {
+			break
+		}
 	}
 
-	return parents, examined
+	return processFamily
 }