support for protecting plugin prameters (vmware#308)

config-reloader/fluentd/parser.go

@@ -43,8 +43,9 @@ type Directive struct {
 
 // Param just holds a Name/Value pair
 type Param struct {
-	Name  string
-	Value string
+	Name      string
+	Value     string
+	Protected bool
 }
 
 // Type return the @type parameter or type parameter. "" if not type is defined
@@ -89,8 +90,9 @@ func (d *Directive) Clone() *Directive {
 
 func (p *Param) Clone() *Param {
 	return &Param{
-		Name:  p.Name,
-		Value: p.Value,
+		Name:      p.Name,
+		Value:     p.Value,
+		Protected: p.Protected,
 	}
 }
 
@@ -115,10 +117,11 @@ func ParamsFromKV(keyValues ...string) Params {
 
 		k := keyValues[i]
 		v := keyValues[i+1]
-		res[k] = &Param{
+		p := protect(&Param{
 			Name:  k,
 			Value: v,
-		}
+		})
+		res[p.Name] = p
 	}
 
 	return res
@@ -288,9 +291,9 @@ func ParseString(s string) (Fragment, error) {
 
 		p := reParam.FindStringSubmatch(line)
 		if len(p) > 0 {
-			param := &Param{
+			param := protect(&Param{
 				Name: p[1],
-			}
+			})
 			if len(p) > 2 {
 				param.Value = p[3]
 				// special handling for @type as it is processed
@@ -315,3 +318,11 @@ func ParseString(s string) (Fragment, error) {
 
 	return res, nil
 }
+
+func protect(p *Param) *Param {
+	if p != nil && !p.Protected && strings.HasPrefix(p.Name, "!") {
+		p.Name = p.Name[1:]
+		p.Protected = true
+	}
+	return p
+}

config-reloader/fluentd/parser_test.go

@@ -219,3 +219,19 @@ func TestParseNested(t *testing.T) {
 	assert.Equal(t, "file", match.Type())
 	assert.Equal(t, "/var/log/fluent/access", match.Param("path"))
 }
+
+func TestProtectedParam(t *testing.T) {
+	dir := Directive{
+		Name:   "ok",
+		Tag:    "tag",
+		Params: ParamsFromKV("a", "1", "!b", "2"),
+	}
+
+	assert.Equal(t, 2, len(dir.Params))
+	assert.False(t, dir.Params["a"].Protected)
+	assert.True(t, dir.Params["b"].Protected)
+
+	params := dir.Params.Clone()
+	assert.False(t, params["a"].Protected)
+	assert.True(t, params["b"].Protected)
+}

config-reloader/processors/extract_plugins.go

@@ -55,8 +55,8 @@ func (p *expandPluginsState) Process(input fluentd.Fragment) (fluentd.Fragment,
 
 		// replace the params
 		for k, v := range replacement.Params {
-			// prefer the params defined at the call site
-			if _, ok := d.Params[k]; !ok {
+			// prefer the params defined at the call site, unless the param is protected
+			if _, ok := d.Params[k]; !ok || v.Protected {
 				d.Params[k] = v.Clone()
 			}
 		}

config-reloader/processors/extract_plugins_test.go

@@ -41,6 +41,8 @@ func TestExpandPlugins(t *testing.T) {
 	username admin
 	buffer_path /hello/world
 	buffer_size 1m
+	!fixed DoNotChange
+	!keep KeepIt
 	<buffer>
 		@type file
 		path /var/log/fluentd.*.buffer
@@ -72,6 +74,10 @@ func TestExpandPlugins(t *testing.T) {
 
   # param is overridden
   buffer_size 5m
+
+  # params are protected
+  fixed Changed
+  !keep Changed
 </match>
 
 <match **>
@@ -107,6 +113,10 @@ func TestExpandPlugins(t *testing.T) {
 	// param that's overridden
 	assert.Equal(t, "5m", matchDir.Param("buffer_size"))
 
+	// params that are protected should remain unchanged
+	assert.Equal(t, "DoNotChange", matchDir.Param("fixed"))
+	assert.Equal(t, "KeepIt", matchDir.Param("keep"))
+
 	// nested content is present
 	assert.Equal(t, "buffer", matchDir.Nested[0].Name)
 	assert.Equal(t, "/var/log/fluentd.*.buffer", matchDir.Nested[0].Param("path"))