Protect entityMetadataMap from concurrent access #197 (#214)

code/go/0chain.net/core/datastore/entity_metadata.go

@@ -1,63 +1,56 @@
 package datastore
 
-type InstanceProvider func() Entity
-
-var entityMetadataMap = make(map[string]EntityMetadata)
-
-/*RegisterEntityProvider - keep track of a list of entity providers. An entity can be registered with multiple names
-* as long as two entities don't use the same name
- */
-func RegisterEntityMetadata(entityName string, entityMetadata EntityMetadata) {
-	entityMetadataMap[entityName] = entityMetadata
-}
-
-/*GetEntityMetadata - return an instance of the entity */
-func GetEntityMetadata(entityName string) EntityMetadata {
-	return entityMetadataMap[entityName]
-}
-
-/*GetEntity - return an instance of the entity */
-func GetEntity(entityName string) Entity {
-	return GetEntityMetadata(entityName).Instance()
-}
-
-type EntityMetadata interface {
-	GetName() string
-	GetDB() string
-	Instance() Entity
-	GetStore() Store
-	GetIDColumnName() string
-}
-
-type EntityMetadataImpl struct {
-	Name         string
-	DB           string
-	Store        Store
-	Provider     InstanceProvider
-	IDColumnName string
-}
-
+type (
+	// InstanceProvider describes the instance function signature.
+	InstanceProvider func() Entity
+
+	// EntityMetadata describes the interface of the metadata entity.
+	EntityMetadata interface {
+		GetName() string
+		GetDB() string
+		Instance() Entity
+		GetStore() Store
+		GetIDColumnName() string
+	}
+
+	// EntityMetadataImpl implements EntityMetadata interface.
+	EntityMetadataImpl struct {
+		Name         string
+		DB           string
+		Store        Store
+		Provider     InstanceProvider
+		IDColumnName string
+	}
+)
+
+// MetadataProvider constructs entity metadata instance.
 func MetadataProvider() *EntityMetadataImpl {
-	em := EntityMetadataImpl{IDColumnName: "id"}
-	return &em
+	return &EntityMetadataImpl{
+		IDColumnName: "id",
+	}
 }
 
+// GetName implements EntityMetadata.GetName method of interface.
 func (em *EntityMetadataImpl) GetName() string {
 	return em.Name
 }
 
+// GetDB implements EntityMetadata.GetDB method of interface.
 func (em *EntityMetadataImpl) GetDB() string {
 	return em.DB
 }
 
+// Instance implements EntityMetadata.Instance method of interface.
 func (em *EntityMetadataImpl) Instance() Entity {
 	return em.Provider()
 }
 
+// GetStore implements EntityMetadata.GetStore method of interface.
 func (em *EntityMetadataImpl) GetStore() Store {
 	return em.Store
 }
 
+// GetIDColumnName implements EntityMetadata.GetIDColumnName method of interface.
 func (em *EntityMetadataImpl) GetIDColumnName() string {
 	return em.IDColumnName
 }

code/go/0chain.net/core/datastore/entity_metadata_store.go

@@ -0,0 +1,45 @@
+package datastore
+
+import (
+	"sync"
+)
+
+type (
+	// entityMetadataStore describes the structure of entity metadata storage
+	// it is safe for concurrent use by multiple read-write operation access.
+	entityMetadataStore struct {
+		store map[string]EntityMetadata // entity metadata storage
+		mutex sync.Mutex                // read-write mutex
+	}
+)
+
+var (
+	// entityMetadataMap keeps instance of entity metadata store.
+	entityMetadataMap = entityMetadataStore{
+		store: make(map[string]EntityMetadata),
+	}
+)
+
+// RegisterEntityMetadata registers an instance of the entity
+// in track of a list of entity providers by given name.
+// An entity can be registered with multiple names
+// as long as two entities don't use the same name.
+func RegisterEntityMetadata(entityName string, entityMetadata EntityMetadata) {
+	entityMetadataMap.mutex.Lock()
+	entityMetadataMap.store[entityName] = entityMetadata
+	entityMetadataMap.mutex.Unlock()
+}
+
+// GetEntityMetadata returns an instance of the entity by name.
+func GetEntityMetadata(entityName string) EntityMetadata {
+	entityMetadataMap.mutex.Lock()
+	em := entityMetadataMap.store[entityName]
+	entityMetadataMap.mutex.Unlock()
+
+	return em
+}
+
+// GetEntity returns an instance of the entity.
+func GetEntity(entityName string) Entity {
+	return GetEntityMetadata(entityName).Instance()
+}