Change Handler.ComResetConnection to return an error

go/mysql/conn.go

@@ -1347,7 +1347,11 @@ func (c *Conn) handleNextCommand(handler Handler) error {
 		// Clean up and reset the connection
 		c.recycleReadPacket()
 		c.discardCursor()
-		handler.ComResetConnection(c)
+		err = handler.ComResetConnection(c)
+		if err != nil {
+			log.Errorf("Error resetting connection (ID %d): %v", c.ConnectionID, err)
+			c.writeErrorPacketFromError(err)
+		}
 		// Reset prepared statements
 		c.PrepareData = make(map[uint32]*PrepareData)
 		err = c.writeOKPacket(0, 0, 0, 0)

go/mysql/server.go

@@ -122,7 +122,11 @@ type Handler interface {
 	WarningCount(c *Conn) uint16
 
 	// ComResetConnection is called when a connection receives a COM_RESET_CONNECTION signal.
-	ComResetConnection(c *Conn)
+	// This is used to reset the session state (e.g. clearing user vars, resetting session vars, releasing
+	// locks, releasing cached prepared statements, etc). One of the primary use cases for COM_RESET_CONNECTION
+	// is to reset a pooled connection's session state so that it can be safely returned to the connection pool
+	// and given to another application process to reuse.
+	ComResetConnection(c *Conn) error
 
 	// ParserOptionsForConnection returns any parser options that should be used for the given connection. For
 	// example, if the connection has enabled ANSI_QUOTES or ANSI SQL_MODE, then the parser needs to know that

go/mysql/server_test.go

@@ -305,8 +305,8 @@ func (th *testHandler) ComStmtExecute(c *Conn, prepare *PrepareData, callback fu
 	}
 }
 
-func (th *testHandler) ComResetConnection(c *Conn) {
-
+func (th *testHandler) ComResetConnection(c *Conn) error {
+	return nil
 }
 
 func (th *testHandler) WarningCount(c *Conn) uint16 {