elasticsearch: support reversed index patterns

Now both [index-]pattern and pattern[-index] are supported

pkg/tsdb/elasticsearch/client/index_pattern.go

@@ -248,14 +248,29 @@ var datePatternReplacements = map[string]string{
 
 func formatDate(t time.Time, pattern string) string {
 	var datePattern string
+	base := ""
+	ltr := false
+
+	if strings.HasPrefix(pattern, "[") {
 		parts := strings.Split(strings.TrimLeft(pattern, "["), "]")
-	base := parts[0]
+		base = parts[0]
 		if len(parts) == 2 {
 			datePattern = parts[1]
 		} else {
 			datePattern = base
 			base = ""
 		}
+		ltr = true
+	} else if strings.HasSuffix(pattern, "]") {
+		parts := strings.Split(strings.TrimRight(pattern, "]"), "[")
+		datePattern = parts[0]
+		if len(parts) == 2 {
+			base = parts[1]
+		} else {
+			base = ""
+		}
+		ltr = false
+	}
 
 	formatted := t.Format(patternToLayout(datePattern))
 
@@ -293,9 +308,13 @@ func formatDate(t time.Time, pattern string) string {
 		formatted = strings.Replace(formatted, "<stdHourNoZero>", fmt.Sprintf("%d", t.Hour()), -1)
 	}
 
+	if ltr {
 		return base + formatted
 	}
 
+	return formatted + base
+}
+
 func patternToLayout(pattern string) string {
 	var match [][]string
 	if match = datePatternRegex.FindAllStringSubmatch(pattern, -1); match == nil {

pkg/tsdb/elasticsearch/client/index_pattern_test.go

@@ -28,29 +28,54 @@ func TestIndexPattern(t *testing.T) {
 		to := fmt.Sprintf("%d", time.Date(2018, 5, 15, 17, 55, 0, 0, time.UTC).UnixNano()/int64(time.Millisecond))
 
 		indexPatternScenario(intervalHourly, "[data-]YYYY.MM.DD.HH", tsdb.NewTimeRange(from, to), func(indices []string) {
-			//So(indices, ShouldHaveLength, 1)
+			So(indices, ShouldHaveLength, 1)
 			So(indices[0], ShouldEqual, "data-2018.05.15.17")
 		})
 
+		indexPatternScenario(intervalHourly, "YYYY.MM.DD.HH[-data]", tsdb.NewTimeRange(from, to), func(indices []string) {
+			So(indices, ShouldHaveLength, 1)
+			So(indices[0], ShouldEqual, "2018.05.15.17-data")
+		})
+
 		indexPatternScenario(intervalDaily, "[data-]YYYY.MM.DD", tsdb.NewTimeRange(from, to), func(indices []string) {
 			So(indices, ShouldHaveLength, 1)
 			So(indices[0], ShouldEqual, "data-2018.05.15")
 		})
 
+		indexPatternScenario(intervalDaily, "YYYY.MM.DD[-data]", tsdb.NewTimeRange(from, to), func(indices []string) {
+			So(indices, ShouldHaveLength, 1)
+			So(indices[0], ShouldEqual, "2018.05.15-data")
+		})
+
 		indexPatternScenario(intervalWeekly, "[data-]GGGG.WW", tsdb.NewTimeRange(from, to), func(indices []string) {
 			So(indices, ShouldHaveLength, 1)
 			So(indices[0], ShouldEqual, "data-2018.20")
 		})
 
+		indexPatternScenario(intervalWeekly, "GGGG.WW[-data]", tsdb.NewTimeRange(from, to), func(indices []string) {
+			So(indices, ShouldHaveLength, 1)
+			So(indices[0], ShouldEqual, "2018.20-data")
+		})
+
 		indexPatternScenario(intervalMonthly, "[data-]YYYY.MM", tsdb.NewTimeRange(from, to), func(indices []string) {
 			So(indices, ShouldHaveLength, 1)
 			So(indices[0], ShouldEqual, "data-2018.05")
 		})
 
+		indexPatternScenario(intervalMonthly, "YYYY.MM[-data]", tsdb.NewTimeRange(from, to), func(indices []string) {
+			So(indices, ShouldHaveLength, 1)
+			So(indices[0], ShouldEqual, "2018.05-data")
+		})
+
 		indexPatternScenario(intervalYearly, "[data-]YYYY", tsdb.NewTimeRange(from, to), func(indices []string) {
 			So(indices, ShouldHaveLength, 1)
 			So(indices[0], ShouldEqual, "data-2018")
 		})
+
+		indexPatternScenario(intervalYearly, "YYYY[-data]", tsdb.NewTimeRange(from, to), func(indices []string) {
+			So(indices, ShouldHaveLength, 1)
+			So(indices[0], ShouldEqual, "2018-data")
+		})
 	})
 
 	Convey("Hourly interval", t, func() {