Fix problems found in QA pass of build 1792795001

internal/procgroup/procgroup.go

@@ -3,6 +3,8 @@ package procgroup
 import (
 	"context"
 	"os/exec"
+	"strconv"
+	"strings"
 	"syscall"
 )
 
@@ -25,6 +27,41 @@ func group(cmd *exec.Cmd) *Cmd {
 	return &Cmd{Cmd: cmd}
 }
 
+// Kill also kills descendants that left the group: agents run their commands in sessions of their own.
 func (cmd *Cmd) Kill() error {
-	return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+	pids := descendants(cmd.Process.Pid)
+	err := syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+	for _, pid := range pids {
+		syscall.Kill(pid, syscall.SIGKILL)
+	}
+	return err
+}
+
+func descendants(root int) []int {
+	out, err := exec.Command("ps", "-A", "-o", "pid=,ppid=").Output()
+	if err != nil {
+		return nil
+	}
+	children := map[int][]int{}
+	for _, line := range strings.Split(string(out), "\n") {
+		f := strings.Fields(line)
+		if len(f) != 2 {
+			continue
+		}
+		pid, err1 := strconv.Atoi(f[0])
+		ppid, err2 := strconv.Atoi(f[1])
+		if err1 != nil || err2 != nil {
+			continue
+		}
+		children[ppid] = append(children[ppid], pid)
+	}
+	pids := []int{}
+	queue := children[root]
+	for len(queue) > 0 {
+		pid := queue[0]
+		queue = queue[1:]
+		pids = append(pids, pid)
+		queue = append(queue, children[pid]...)
+	}
+	return pids
 }