test(agent/agentssh): fix test race and improve Windows compat (#17271)

Fixes coder/internal#558

agent/agentssh/agentssh.go

@@ -1060,8 +1060,10 @@ func (s *Server) Close() error {
 	// Guard against multiple calls to Close and
 	// accepting new connections during close.
 	if s.closing != nil {
+		closing := s.closing
 		s.mu.Unlock()
-		return xerrors.New("server is closing")
+		<-closing
+		return xerrors.New("server is closed")
 	}
 	s.closing = make(chan struct{})
 

agent/agentssh/agentssh_test.go

@@ -153,7 +153,9 @@ func TestNewServer_CloseActiveConnections(t *testing.T) {
 		logger := slogtest.Make(t, &slogtest.Options{IgnoreErrors: true}).Leveled(slog.LevelDebug)
 		s, err := agentssh.NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
 		require.NoError(t, err)
-		defer s.Close()
+		t.Cleanup(func() {
+			_ = s.Close()
+		})
 		err = s.UpdateHostSigner(42)
 		assert.NoError(t, err)
 
@@ -190,10 +192,17 @@ func TestNewServer_CloseActiveConnections(t *testing.T) {
 				}
 				// The 60 seconds here is intended to be longer than the
 				// test. The shutdown should propagate.
-				err = sess.Start("/bin/bash -c 'trap \"sleep 60\" SIGTERM; sleep 60'")
+				if runtime.GOOS == "windows" {
+					// Best effort to at least partially test this in Windows.
+					err = sess.Start("echo start\"ed\" && sleep 60")
+				} else {
+					err = sess.Start("/bin/bash -c 'trap \"sleep 60\" SIGTERM; echo start\"ed\"; sleep 60'")
+				}
 				assert.NoError(t, err)
 
+				pty.ExpectMatchContext(ctx, "started")
 				close(ch)
+
 				err = sess.Wait()
 				assert.Error(t, err)
 			}(waitConns[i])

agent/agentssh/exec_windows.go

@@ -2,7 +2,6 @@ package agentssh
 
 import (
 	"context"
-	"os"
 	"os/exec"
 	"syscall"
 
@@ -15,7 +14,12 @@ func cmdSysProcAttr() *syscall.SysProcAttr {
 
 func cmdCancel(ctx context.Context, logger slog.Logger, cmd *exec.Cmd) func() error {
 	return func() error {
-		logger.Debug(ctx, "cmdCancel: sending interrupt to process", slog.F("pid", cmd.Process.Pid))
-		return cmd.Process.Signal(os.Interrupt)
+		logger.Debug(ctx, "cmdCancel: killing process", slog.F("pid", cmd.Process.Pid))
+		// Windows doesn't support sending signals to process groups, so we
+		// have to kill the process directly. In the future, we may want to
+		// implement a more sophisticated solution for process groups on
+		// Windows, but for now, this is a simple way to ensure that the
+		// process is terminated when the context is cancelled.
+		return cmd.Process.Kill()
 	}
 }