Support extra params for cache server db connection (#5599)

* support extra params for db connection

* using built-in json library instead of casting

backend/src/cache/client_manager.go

@@ -20,6 +20,7 @@ import (
 	"log"
 	"time"
 
+	"encoding/json"
 	"github.com/cenkalti/backoff"
 	"github.com/golang/glog"
 	"github.com/jinzhu/gorm"
@@ -103,6 +104,10 @@ func initDBClient(params WhSvrDBParameters, initConnectionTimeout time.Duration)
 }
 
 func initMysql(params WhSvrDBParameters, initConnectionTimeout time.Duration) string {
+
+	var mysqlExtraParams = map[string]string{}
+	data := []byte(params.dbExtraParams)
+	json.Unmarshal(data, &mysqlExtraParams)
 	mysqlConfig := client.CreateMySQLConfig(
 		params.dbUser,
 		params.dbPwd,
@@ -110,7 +115,7 @@ func initMysql(params WhSvrDBParameters, initConnectionTimeout time.Duration) st
 		params.dbPort,
 		"",
 		params.dbGroupConcatMaxLen,
-		map[string]string{},
+		mysqlExtraParams,
 	)
 
 	var db *sql.DB

backend/src/cache/main.go

@@ -52,6 +52,7 @@ type WhSvrDBParameters struct {
 	dbUser              string
 	dbPwd               string
 	dbGroupConcatMaxLen string
+	dbExtraParams       string
 	namespaceToWatch    string
 }
 
@@ -65,6 +66,7 @@ func main() {
 	flag.StringVar(&params.dbUser, "db_user", "root", "Database user name.")
 	flag.StringVar(&params.dbPwd, "db_password", "", "Database password.")
 	flag.StringVar(&params.dbGroupConcatMaxLen, "db_group_concat_max_len", mysqlDBGroupConcatMaxLenDefault, "Database group concat max length.")
+	flag.StringVar(&params.dbExtraParams, "db_extra_params", "", "Database extra parameters.")
 	flag.StringVar(&params.namespaceToWatch, "namespace_to_watch", "kubeflow", "Namespace to watch.")
 	// Use default value of client QPS (5) & burst (10) defined in
 	// k8s.io/client-go/rest/config.go#RESTClientFor