osbuild/osbuild-exec: add file for monitor to options

If opts.MonitorFile is set, the monitor output is written to a separate
FD which corresponds with the specified file.

Author: croissanne

pkg/osbuild/osbuild-exec.go

@@ -43,8 +43,10 @@ type OSBuildOptions struct {
 	Stdout     io.Writer
 	Stderr     io.Writer
 
-	Monitor   MonitorType
-	MonitorFD uintptr
+	// If MonitorFD is set, a file (MonitorW) needs to be inherited by the osbuild process. The
+	// caller should make sure to close it afterwards.
+	Monitor     MonitorType
+	MonitorFile *os.File
 
 	JSONOutput bool
 
@@ -79,8 +81,10 @@ func NewOSBuildCmd(manifest []byte, optsPtr *OSBuildOptions) *exec.Cmd {
 	if opts.Monitor != "" {
 		cmd.Args = append(cmd.Args, fmt.Sprintf("--monitor=%s", opts.Monitor))
 	}
-	if opts.MonitorFD != 0 {
-		cmd.Args = append(cmd.Args, fmt.Sprintf("--monitor-fd=%d", opts.MonitorFD))
+
+	if opts.MonitorFile != nil {
+		cmd.Args = append(cmd.Args, "--monitor-fd=3")
+		cmd.ExtraFiles = []*os.File{opts.MonitorFile}
 	}
 
 	if opts.JSONOutput {

pkg/osbuild/osbuild-exec_test.go

@@ -51,6 +51,8 @@ func TestNewOSBuildCmdNilOptions(t *testing.T) {
 
 func TestNewOSBuildCmdFullOptions(t *testing.T) {
 	mf := []byte(`{"real": "manifest"}`)
+	_, wp, err := os.Pipe()
+	assert.NoError(t, err)
 	cmd := osbuild.NewOSBuildCmd(
 		mf,
 		&osbuild.OSBuildOptions{
@@ -63,7 +65,7 @@ func TestNewOSBuildCmdFullOptions(t *testing.T) {
 			Checkpoints:  []string{"checkpoint-1", "checkpoint-2"},
 			ExtraEnv:     []string{"EXTRA_ENV_1=1", "EXTRA_ENV_2=2"},
 			Monitor:      osbuild.MonitorLog,
-			MonitorFD:    10,
+			MonitorFile:  wp,
 			JSONOutput:   true,
 			CacheMaxSize: 10 * datasizes.GiB,
 		},
@@ -89,7 +91,7 @@ func TestNewOSBuildCmdFullOptions(t *testing.T) {
 			"--checkpoint",
 			"checkpoint-2",
 			"--monitor=LogMonitor",
-			"--monitor-fd=10",
+			"--monitor-fd=3",
 			"--json",
 		},
 		cmd.Args,
@@ -101,6 +103,8 @@ func TestNewOSBuildCmdFullOptions(t *testing.T) {
 	stdin, err := io.ReadAll(cmd.Stdin)
 	assert.NoError(t, err)
 	assert.Equal(t, mf, stdin)
+
+	assert.Equal(t, wp, cmd.ExtraFiles[0])
 }
 
 func TestRunOSBuildJSONOutput(t *testing.T) {
@@ -157,6 +161,44 @@ osbuild-stderr-output
 	assert.Empty(t, stderr.Bytes())
 }
 
+func TestRunOSBuildMonitor(t *testing.T) {
+	fakeOSBuildBinary := makeFakeOSBuild(t, `
+>&3 echo -n '{"some": "monitor"}'
+
+if [ "$1" = "--version" ]; then
+    echo '90000.0'
+else
+    echo -n osbuild-stdout-output
+fi
+>&2 echo -n osbuild-stderr-output
+`)
+	restore := osbuild.MockOSBuildCmd(fakeOSBuildBinary)
+	defer restore()
+
+	rp, wp, err := os.Pipe()
+	assert.NoError(t, err)
+	defer wp.Close()
+
+	var stdout, stderr bytes.Buffer
+	opts := &osbuild.OSBuildOptions{
+		Stdout:      &stdout,
+		Stderr:      &stderr,
+		Monitor:     osbuild.MonitorJSONSeq,
+		MonitorFile: wp,
+	}
+
+	// without json output set the result will be empty
+	_, err = osbuild.RunOSBuild(nil, opts)
+	assert.NoError(t, err)
+	assert.NoError(t, wp.Close())
+
+	monitorOutput, err := io.ReadAll(rp)
+	assert.NoError(t, err)
+	assert.Equal(t, `{"some": "monitor"}`, string(monitorOutput))
+	assert.Equal(t, "osbuild-stdout-output", stdout.String())
+	assert.Equal(t, "osbuild-stderr-output", stderr.String())
+}
+
 func TestSyncWriter(t *testing.T) {
 	var mu sync.Mutex
 	var buf bytes.Buffer