Fix combined tagdrop/tagpass filtering (#3031)

internal/models/filter.go

@@ -175,7 +175,8 @@ func (f *Filter) shouldFieldPass(key string) bool {
 // shouldTagsPass returns true if the metric should pass, false if should drop
 // based on the tagdrop/tagpass filter parameters
 func (f *Filter) shouldTagsPass(tags map[string]string) bool {
-	if f.TagPass != nil {
+
+	tagPass := func(f *Filter) bool {
 		for _, pat := range f.TagPass {
 			if pat.filter == nil {
 				continue
@@ -189,7 +190,7 @@ func (f *Filter) shouldTagsPass(tags map[string]string) bool {
 		return false
 	}
 
-	if f.TagDrop != nil {
+	tagDrop := func(f *Filter) bool {
 		for _, pat := range f.TagDrop {
 			if pat.filter == nil {
 				continue
@@ -203,6 +204,18 @@ func (f *Filter) shouldTagsPass(tags map[string]string) bool {
 		return true
 	}
 
+	// Add additional logic in case where both parameters are set.
+	// see: https://github.com/influxdata/telegraf/issues/2860
+	if f.TagPass != nil && f.TagDrop != nil {
+		// return true only in case when tag pass and won't be dropped (true, true).
+		// in case when the same tag should be passed and dropped it will be dropped (true, false).
+		return tagPass(f) && tagDrop(f)
+	} else if f.TagPass != nil {
+		return tagPass(f)
+	} else if f.TagDrop != nil {
+		return tagDrop(f)
+	}
+
 	return true
 }
 

internal/models/filter_test.go

@@ -357,3 +357,48 @@ func TestFilter_FilterTagsMatches(t *testing.T) {
 		"mytag": "foobar",
 	}, pretags)
 }
+
+// TestFilter_FilterTagsPassAndDrop used for check case when
+// both parameters were defined
+// see: https://github.com/influxdata/telegraf/issues/2860
+func TestFilter_FilterTagsPassAndDrop(t *testing.T) {
+
+	inputData := []map[string]string{
+		{"tag1": "1", "tag2": "3"},
+		{"tag1": "1", "tag2": "2"},
+		{"tag1": "2", "tag2": "1"},
+		{"tag1": "4", "tag2": "1"},
+	}
+
+	expectedResult := []bool{false, true, false, false}
+
+	filterPass := []TagFilter{
+		TagFilter{
+			Name:   "tag1",
+			Filter: []string{"1", "4"},
+		},
+	}
+
+	filterDrop := []TagFilter{
+		TagFilter{
+			Name:   "tag1",
+			Filter: []string{"4"},
+		},
+		TagFilter{
+			Name:   "tag2",
+			Filter: []string{"3"},
+		},
+	}
+
+	f := Filter{
+		TagDrop: filterDrop,
+		TagPass: filterPass,
+	}
+
+	require.NoError(t, f.Compile())
+
+	for i, tag := range inputData {
+		assert.Equal(t, f.shouldTagsPass(tag), expectedResult[i])
+	}
+
+}