add alias+datastream rollover, and auto rollover on index tpl change (#40)

fixes #37

pkg/es/index_template.go

@@ -127,26 +127,28 @@ func IndexTemplateShow(conf *cfg.Config, tplname string) error {
 	table = printer.NewTable(conf, 2, 0)
 	table.Addheaders("index field mapping", "type")
 
-	for name, field := range tpl.IndexTemplate.Template.Mappings.Properties {
-		typeval := ""
+	if tpl.IndexTemplate.Template.Mappings != nil {
+		for name, field := range tpl.IndexTemplate.Template.Mappings.Properties {
+			typeval := ""
 
-		switch val := field.(type) {
-		case *types.IntegerNumberProperty:
-			typeval = val.Type
-		case *types.KeywordProperty:
-			typeval = val.Type
-		case *types.DateProperty:
-			typeval = val.Type
+			switch val := field.(type) {
+			case *types.IntegerNumberProperty:
+				typeval = val.Type
+			case *types.KeywordProperty:
+				typeval = val.Type
+			case *types.DateProperty:
+				typeval = val.Type
+			}
+
+			table.Entries = append(table.Entries, []string{
+				name, typeval,
+			})
 		}
 
-		table.Entries = append(table.Entries, []string{
-			name, typeval,
-		})
-	}
-
-	fmt.Println()
-	if err := table.Print(); err != nil {
-		return err
+		fmt.Println()
+		if err := table.Print(); err != nil {
+			return err
+		}
 	}
 
 	return nil
@@ -343,6 +345,12 @@ func IndexTemplateModify(conf *cfg.Config, name string, mappings []string) error
 		return fmt.Errorf("failed to modify index template: %s", esErrorString(err))
 	}
 
+	if conf.Rollover {
+		if err := rolloverAliasIndexTemplate(conf, name); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 
@@ -358,6 +366,72 @@ func IndexTemplateDelete(conf *cfg.Config, name string) error {
 	return nil
 }
 
+// Based on given  index template find the  associated index patterns,
+// find  indices matching  those,  find their  associated aliases  and
+// rollover all we find. Only run when conf.Rollover==true
+func rolloverAliasIndexTemplate(conf *cfg.Config, name string) error {
+	res, err := conf.DefaultCluster.ES.Indices.GetIndexTemplate().
+		Name(name).
+		Do(context.Background())
+
+	if err != nil {
+		return fmt.Errorf("failed to get index template: %s", esErrorString(err))
+	}
+
+	slog.Debug("res", "index template", res)
+
+	if len(res.IndexTemplates) != 1 {
+		return errors.New("multiple or no index template matched the pattern")
+	}
+
+	patterns := res.IndexTemplates[0].IndexTemplate.IndexPatterns
+	aliases := map[string]int{}
+
+	// find all aliases matching the patterns
+	for _, pattern := range patterns {
+		res, err := conf.DefaultCluster.ES.Indices.ResolveIndex(pattern).
+			Do(context.Background())
+		if err != nil {
+			return fmt.Errorf("failed to resolve index pattern: %s", esErrorString(err))
+		}
+
+		for _, index := range res.Indices {
+			for _, alias := range index.Aliases {
+				aliases[alias] = 1
+			}
+		}
+	}
+
+	if len(aliases) == 0 {
+		return nil
+	}
+
+	table := printer.NewTable(conf, 4, 0)
+	table.Addheaders("rollover alias", "status", "ack", "new index")
+
+	// apply rollover to all matching aliases, if any
+	for alias := range aliases {
+		res, err := RolloverAlias(conf, alias)
+		if err != nil {
+			return err
+		}
+
+		table.Entries = append(table.Entries, []string{
+			alias,
+			fmt.Sprintf("%t", res.RolledOver),
+			fmt.Sprintf("%t", res.Acknowledged),
+			res.NewIndex,
+		})
+
+		if err := table.Print(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+
+}
+
 func modMappings(mappings []string) (types.TypeMappingVariant, error) {
 	typemaps := esdsl.NewTypeMapping()