atelet: add the empty_dir volume source

cmd/atelet/main.go

@@ -1573,7 +1573,7 @@ func buildAteomWorkloadSpec(spec *ateletpb.WorkloadSpec, containerSpecs []*ateom
 					VolumeName: volName,
 					MountPath:  vm.GetMountPath(),
 				})
-			case *ateletpb.Volume_External:
+			case *ateletpb.Volume_External, *ateletpb.Volume_EmptyDir:
 				csiMounts = append(csiMounts, &ateompb.VolumeMount{
 					VolumeName: volName,
 					MountPath:  vm.GetMountPath(),

cmd/atelet/main_test.go

@@ -1022,6 +1022,7 @@ func TestBuildAteomWorkloadSpecForwardsDurableDirMounts(t *testing.T) {
 			{Name: "data", Source: &ateletpb.Volume_DurableDir{DurableDir: &ateletpb.DurableDirVolume{}}},
 			{Name: "cache", Source: &ateletpb.Volume_DurableDir{DurableDir: &ateletpb.DurableDirVolume{}}},
 			{Name: "scratch", Source: &ateletpb.Volume_External{External: &ateletpb.ExternalVolumeSource{}}},
+			{Name: "empty", Source: &ateletpb.Volume_EmptyDir{EmptyDir: &ateletpb.EmptyDirVolume{}}},
 			{Name: "system-info", Source: &ateletpb.Volume_SystemInfo{SystemInfo: &ateletpb.SystemInfoVolume{}}},
 		},
 		Containers: []*ateletpb.Container{
@@ -1031,6 +1032,7 @@ func TestBuildAteomWorkloadSpecForwardsDurableDirMounts(t *testing.T) {
 					{Name: "data", MountPath: "/home/counter"},
 					{Name: "cache", MountPath: "/var/cache"},
 					{Name: "scratch", MountPath: "/scratch"},
+					{Name: "empty", MountPath: "/empty"},
 					{Name: "system-info", MountPath: "/run/ate"},
 				},
 			},
@@ -1055,6 +1057,7 @@ func TestBuildAteomWorkloadSpecForwardsDurableDirMounts(t *testing.T) {
 				},
 				CsiVolumeMounts: []*ateompb.VolumeMount{
 					{VolumeName: "scratch", MountPath: "/scratch"},
+					{VolumeName: "empty", MountPath: "/empty"},
 				},
 				SystemInfoVolumeMounts: []*ateompb.SystemInfoVolumeMount{
 					{VolumeName: "system-info", MountPath: "/run/ate"},

cmd/atelet/volumes.go

@@ -31,11 +31,17 @@ import (
 
 func (s *AteomHerder) mountExternalVolumes(ctx context.Context, actorUID string, volumes []*ateletpb.Volume) error {
 	for _, vol := range volumes {
+		hostPath := ateletpath.VolumeHostPath(actorUID, vol.GetName())
+		if vol.GetEmptyDir() != nil {
+			if err := resetEmptyDir(hostPath); err != nil {
+				return err
+			}
+			continue
+		}
 		ext := vol.GetExternal()
 		if ext == nil {
 			continue
 		}
-		hostPath := ateletpath.VolumeHostPath(actorUID, vol.GetName())
 		if err := os.MkdirAll(hostPath, 0o750); err != nil {
 			return fmt.Errorf("failed to create mount point %q: %w", hostPath, err)
 		}
@@ -56,6 +62,16 @@ func (s *AteomHerder) mountExternalVolumes(ctx context.Context, actorUID string,
 	return nil
 }
 
+func resetEmptyDir(hostPath string) error {
+	if err := os.RemoveAll(hostPath); err != nil {
+		return fmt.Errorf("failed to clear empty dir %q: %w", hostPath, err)
+	}
+	if err := os.MkdirAll(hostPath, 0o750); err != nil {
+		return fmt.Errorf("failed to create empty dir %q: %w", hostPath, err)
+	}
+	return nil
+}
+
 func (s *AteomHerder) unmountExternalVolumes(ctx context.Context, actorUID string, volumes []*ateletpb.Volume) error {
 	var errs []error
 	for _, vol := range volumes {

cmd/atelet/volumes_test.go

@@ -570,3 +570,23 @@ func TestDirectCSIDriverConfigGetter(t *testing.T) {
 		t.Fatalf("expected error for missing driver, got nil")
 	}
 }
+
+func TestResetEmptyDirClearsPreviousContents(t *testing.T) {
+	dir := filepath.Join(t.TempDir(), "volumes", "shared")
+	if err := os.MkdirAll(dir, 0o750); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "stale"), []byte("x"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := resetEmptyDir(dir); err != nil {
+		t.Fatalf("resetEmptyDir: %v", err)
+	}
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatalf("ReadDir: %v", err)
+	}
+	if len(entries) != 0 {
+		t.Fatalf("dir still has %d entries after reset", len(entries))
+	}
+}