DB RPC driver: add master/replica support (#17792)

Automatic Merge

plugin/client.go

@@ -56,6 +56,7 @@ func (p *MattermostPlugin) SetHelpers(helpers Helpers) {
 	p.Helpers = helpers
 }
 
+// SetDriver sets the RPC client implementation to talk with the server.
 func (p *MattermostPlugin) SetDriver(driver Driver) {
 	p.Driver = driver
 }

plugin/db_rpc.go

@@ -42,9 +42,9 @@ type Z_DbBoolReturn struct {
 	A bool
 }
 
-func (db *dbRPCClient) Conn() (string, error) {
+func (db *dbRPCClient) Conn(isMaster bool) (string, error) {
 	ret := &Z_DbStrErrReturn{}
-	err := db.client.Call("Plugin.Conn", struct{}{}, ret)
+	err := db.client.Call("Plugin.Conn", isMaster, ret)
 	if err != nil {
 		log.Printf("error during Plugin.Conn: %v", err)
 	}
@@ -52,8 +52,8 @@ func (db *dbRPCClient) Conn() (string, error) {
 	return ret.A, ret.B
 }
 
-func (db *dbRPCServer) Conn(_ struct{}, ret *Z_DbStrErrReturn) error {
-	ret.A, ret.B = db.dbImpl.Conn()
+func (db *dbRPCServer) Conn(isMaster bool, ret *Z_DbStrErrReturn) error {
+	ret.A, ret.B = db.dbImpl.Conn(isMaster)
 	ret.B = encodableError(ret.B)
 	return nil
 }

plugin/helpers.go

@@ -109,9 +109,13 @@ type ResultContainer struct {
 	RowsAffectedError error
 }
 
+// Driver is a sql driver interface that is used by plugins to perform
+// raw SQL queries without opening DB connections by themselves. This interface
+// is not subject to backward compatibility guarantees and is only meant to be
+// used by plugins built by the Mattermost team.
 type Driver interface {
 	// Connection
-	Conn() (string, error)
+	Conn(isMaster bool) (string, error)
 	ConnPing(connID string) error
 	ConnClose(connID string) error
 	ConnQuery(connID, q string, args []driver.NamedValue) (string, error)         // rows