rc: add ability for options blocks to register reload functions

fs/rc/config.go

@@ -8,13 +8,23 @@ import (
 	"github.com/pkg/errors"
 )
 
-var optionBlock = map[string]interface{}{}
+var (
+	optionBlock  = map[string]interface{}{}
+	optionReload = map[string]func() error{}
+)
 
 // AddOption adds an option set
 func AddOption(name string, option interface{}) {
 	optionBlock[name] = option
 }
 
+// AddOptionReload adds an option set with a reload function to be
+// called when options are changed
+func AddOptionReload(name string, option interface{}, reload func() error) {
+	optionBlock[name] = option
+	optionReload[name] = reload
+}
+
 func init() {
 	Add(Call{
 		Path:  "options/blocks",
@@ -103,7 +113,12 @@ func rcOptionsSet(in Params) (out Params, err error) {
 		if err != nil {
 			return nil, errors.Wrapf(err, "failed to write options from block %q", name)
 		}
-
+		if reload := optionReload[name]; reload != nil {
+			err = reload()
+			if err != nil {
+				return nil, errors.Wrapf(err, "failed to reload options from block %q", name)
+			}
+		}
 	}
 	return out, nil
 }

fs/rc/config_test.go

@@ -1,8 +1,10 @@
 package rc
 
 import (
+	"fmt"
 	"testing"
 
+	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -24,9 +26,21 @@ func TestAddOption(t *testing.T) {
 	assert.Equal(t, len(optionBlock), 0)
 	AddOption("potato", &testOptions)
 	assert.Equal(t, len(optionBlock), 1)
+	assert.Equal(t, len(optionReload), 0)
 	assert.Equal(t, &testOptions, optionBlock["potato"])
 }
 
+func TestAddOptionReload(t *testing.T) {
+	defer clearOptionBlock()
+	assert.Equal(t, len(optionBlock), 0)
+	reload := func() error { return nil }
+	AddOptionReload("potato", &testOptions, reload)
+	assert.Equal(t, len(optionBlock), 1)
+	assert.Equal(t, len(optionReload), 1)
+	assert.Equal(t, &testOptions, optionBlock["potato"])
+	assert.Equal(t, fmt.Sprintf("%p", reload), fmt.Sprintf("%p", optionReload["potato"]))
+}
+
 func TestOptionsBlocks(t *testing.T) {
 	defer clearOptionBlock()
 	AddOption("potato", &testOptions)
@@ -53,7 +67,14 @@ func TestOptionsGet(t *testing.T) {
 
 func TestOptionsSet(t *testing.T) {
 	defer clearOptionBlock()
-	AddOption("potato", &testOptions)
+	var reloaded int
+	AddOptionReload("potato", &testOptions, func() error {
+		if reloaded > 0 {
+			return errors.New("error while reloading")
+		}
+		reloaded++
+		return nil
+	})
 	call := Calls.Get("options/set")
 	require.NotNil(t, call)
 
@@ -67,6 +88,12 @@ func TestOptionsSet(t *testing.T) {
 	require.Nil(t, out)
 	assert.Equal(t, 50, testOptions.Int)
 	assert.Equal(t, "hello", testOptions.String)
+	assert.Equal(t, 1, reloaded)
+
+	// error from reload
+	_, err = call.Fn(in)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "error while reloading")
 
 	// unknown option block
 	in = Params{
@@ -85,4 +112,5 @@ func TestOptionsSet(t *testing.T) {
 	_, err = call.Fn(in)
 	require.Error(t, err)
 	assert.Contains(t, err.Error(), "failed to write options")
+
 }