Add MySQL db max idle connections and connections lifetime assignment (…

…#4211)

Allow the storage backend for MySQL to use a custom connection lifetime and max idle connection value if the parameter is specified in the config file of vault otherwise do not set in order to leave at default value.

physical/mysql/mysql.go

@@ -71,6 +71,30 @@ func NewMySQLBackend(conf map[string]string, logger log.Logger) (physical.Backen
 	}
 	dbTable := database + "." + table
 
+       maxIdleConnStr, ok := conf["max_idle_connections"]
+	var maxIdleConnInt int = nil
+	if ok {
+		maxParmaxIdleConnInt, err = strconv.Atoi(maxIdleConnStr)
+		if err != nil {
+			return nil, errwrap.Wrapf("failed parsing max_idle_connections parameter: {{err}}", err)
+		}
+		if logger.IsDebug() {
+			logger.Debug("mysql: max_idle_connections set", "max_idle_connections", maxIdleConnInt)
+		}
+	}
+
+       maxConnLifeStr, ok := conf["max_connection_lifetime"]
+	var maxConnLifeInt int = nil
+	if ok {
+		maxConnLifeInt, err = strconv.Atoi(maxConnLifeStr)
+		if err != nil {
+			return nil, errwrap.Wrapf("failed parsing max_connection_lifetime parameter: {{err}}", err)
+		}
+		if logger.IsDebug() {
+			logger.Debug("mysql: max_connection_lifetime set", "max_connection_lifetime", maxConnLifeInt)
+		}
+	}
+
 	maxParStr, ok := conf["max_parallel"]
 	var maxParInt int
 	if ok {
@@ -101,9 +125,13 @@ func NewMySQLBackend(conf map[string]string, logger log.Logger) (physical.Backen
 	if err != nil {
 		return nil, fmt.Errorf("failed to connect to mysql: %v", err)
 	}
-
 	db.SetMaxOpenConns(maxParInt)
-
+	if maxIdleConnInt != nil {
+		db.SetMaxIdleConns(maxIdleConnInt)
+	}
+	if maxConnLifeInt != nil {
+		db.SetConnMaxLifetime(time.Second * maxConnLifeInt)
+	}
 	// Check schema exists
 	var schemaExist bool
 	schemaRows, err := db.Query("SELECT SCHEMA_NAME FROM information_schema.SCHEMATA WHERE SCHEMA_NAME = ?", database)