Add missing period_config root block to doc generator (#7981)

**What this PR does / why we need it**:
Update doc generator tool to validate if slice element is a root block.

Add missing `period_config` root block to doc generator tool.

**Special notes for your reviewer**:

**Checklist**
- [ ] Documentation updated

docs/sources/configuration/_index.md

@@ -3610,6 +3610,55 @@ fifocache:
 [async_cache_write_back_buffer_size: <int> | default = 500]
 ```
 
+### period_config
+
+The `period_config` block configures what index schemas should be used for from specific time periods.
+
+```yaml
+# The date of the first day that index buckets should be created. Use a date in
+# the past if this is your only period_config, otherwise use a date when you
+# want the schema to switch over. In YYYY-MM-DD format, for example: 2018-04-15.
+[from: <daytime>]
+
+# store and object_store below affect which <storage_config> key is used.
+# Which store to use for the index. Either aws, aws-dynamo, gcp, bigtable,
+# bigtable-hashed, cassandra, boltdb or boltdb-shipper.
+[store: <string> | default = ""]
+
+# Which store to use for the chunks. Either aws, azure, gcp, bigtable, gcs,
+# cassandra, swift or filesystem. If omitted, defaults to the same value as
+# store.
+[object_store: <string> | default = ""]
+
+# The schema version to use, current recommended schema is v11.
+[schema: <string> | default = ""]
+
+# Configures how the index is updated and stored.
+index:
+  # Table prefix for all period tables.
+  [prefix: <string> | default = ""]
+
+  # Table period.
+  [period: <duration>]
+
+  # A map to be added to all managed tables.
+  [tags: <map of string to string>]
+
+# Configured how the chunks are updated and stored.
+chunks:
+  # Table prefix for all period tables.
+  [prefix: <string> | default = ""]
+
+  # Table period.
+  [period: <duration>]
+
+  # A map to be added to all managed tables.
+  [tags: <map of string to string>]
+
+# How many shards will be created. Only used if schema is v10 or greater.
+[row_shards: <int>]
+```
+
 ### azure_storage_config
 
 The `azure_storage_config` block configures the connection to Azure object storage backend. The supported CLI flags `<prefix>` used to reference this configuration block are:

pkg/storage/config/schema_config.go

@@ -91,13 +91,13 @@ type PeriodConfig struct {
 	// used when working with config
 	From DayTime `yaml:"from" doc:"description=The date of the first day that index buckets should be created. Use a date in the past if this is your only period_config, otherwise use a date when you want the schema to switch over. In YYYY-MM-DD format, for example: 2018-04-15."`
 	// type of index client to use.
-	IndexType string `yaml:"store"`
+	IndexType string `yaml:"store" doc:"description=store and object_store below affect which <storage_config> key is used.\nWhich store to use for the index. Either aws, aws-dynamo, gcp, bigtable, bigtable-hashed, cassandra, boltdb or boltdb-shipper. "`
 	// type of object client to use; if omitted, defaults to store.
-	ObjectType  string              `yaml:"object_store"`
+	ObjectType  string              `yaml:"object_store" doc:"description=Which store to use for the chunks. Either aws, azure, gcp, bigtable, gcs, cassandra, swift or filesystem. If omitted, defaults to the same value as store."`
-	Schema      string              `yaml:"schema"`
+	Schema      string              `yaml:"schema" doc:"description=The schema version to use, current recommended schema is v11."`
-	IndexTables PeriodicTableConfig `yaml:"index"`
+	IndexTables PeriodicTableConfig `yaml:"index" doc:"description=Configures how the index is updated and stored."`
-	ChunkTables PeriodicTableConfig `yaml:"chunks"`
+	ChunkTables PeriodicTableConfig `yaml:"chunks" doc:"description=Configured how the chunks are updated and stored."`
-	RowShards   uint32              `yaml:"row_shards"`
+	RowShards   uint32              `yaml:"row_shards" doc:"description=How many shards will be created. Only used if schema is v10 or greater."`
 
 	// Integer representation of schema used for hot path calculation. Populated on unmarshaling.
 	schemaInt *int `yaml:"-"`
@@ -369,9 +369,9 @@ func (cfg *PeriodConfig) VersionAsInt() (int, error) {
 
 // PeriodicTableConfig is configuration for a set of time-sharded tables.
 type PeriodicTableConfig struct {
-	Prefix string
+	Prefix string        `yaml:"prefix" doc:"description=Table prefix for all period tables."`
-	Period time.Duration
+	Period time.Duration `yaml:"period" doc:"description=Table period."`
-	Tags   Tags
+	Tags   Tags          `yaml:"tags" doc:"description=A map to be added to all managed tables."`
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.

tools/doc-generator/parse/parser.go

@@ -256,16 +256,30 @@ func config(block *ConfigBlock, cfg interface{}, flags map[uintptr]*flag.Flag, r
 			_, isCustomType := getFieldCustomType(field.Type)
 			isSliceOfStructs := field.Type.Kind() == reflect.Slice && (field.Type.Elem().Kind() == reflect.Struct || field.Type.Elem().Kind() == reflect.Ptr)
 			if !isCustomType && isSliceOfStructs {
+				// Check if slice element type is a root block
+				// and add it to the blocks structure
+				rootName, rootDesc, isRoot := isRootBlock(field.Type.Elem(), rootBlocks)
+				if isRoot {
+					sliceElementBlock, err := config(nil, reflect.New(field.Type.Elem()).Interface(), flags, rootBlocks)
+					if err != nil {
+						return nil, errors.Wrapf(err, "couldn't inspect slice, element_type=%s", field.Type.Elem())
+					}
+					if len(sliceElementBlock) == 1 {
+						element = &ConfigBlock{
+							Name:    rootName,
+							Desc:    rootDesc,
+							Entries: sliceElementBlock[0].Entries,
+						}
+						blocks = append(blocks, element)
+					}
+				}
+
+				// Add slice element to current block
 				element = &ConfigBlock{
 					Name: fieldName,
 					Desc: getFieldDescription(cfg, field, ""),
 				}
 				kind = KindSlice
-
-				_, err = config(element, reflect.New(field.Type.Elem()).Interface(), flags, rootBlocks)
-				if err != nil {
-					return nil, errors.Wrapf(err, "couldn't inspect slice, element_type=%s", field.Type.Elem())
-				}
 			}
 		}
 
@@ -338,6 +352,8 @@ func getFieldCustomType(t reflect.Type) (string, bool) {
 		return "url", true
 	case reflect.TypeOf(time.Duration(0)).String():
 		return "duration", true
+	case reflect.TypeOf(storage_config.DayTime{}).String():
+		return "daytime", true
 	case reflect.TypeOf(flagext.StringSliceCSV{}).String():
 		return fieldString, true
 	case reflect.TypeOf(flagext.CIDRSliceCSV{}).String():
@@ -421,6 +437,8 @@ func getCustomFieldType(t reflect.Type) (string, bool) {
 		return "url", true
 	case reflect.TypeOf(time.Duration(0)).String():
 		return "duration", true
+	case reflect.TypeOf(storage_config.DayTime{}).String():
+		return "daytime", true
 	case reflect.TypeOf(flagext.StringSliceCSV{}).String():
 		return fieldString, true
 	case reflect.TypeOf(flagext.CIDRSliceCSV{}).String():