4 ms·

Is it possible to get stale reads from non-primary nodes in a single-primary setup?

• morgo 10y ago
  In single primary the other nodes are put in a read-only mode so they can not accept writes. So stale reads can not happen. To expand on your question a little - the MySQL router currently works better for single primary (it supports multi-primary but does not prevent stale reads). If you go third party, ProxySQL also supports Group Replication natively with multi-primary: http://lefred.be/content/mysql-group-replication-native-support-in-proxysql/ http://lefred.be/content/mysql-group-replication-native-supp... I was chatting to the author about this at FOSDEM - since it is possible to keep track of nodes state by following GTIDs executed in the binary log stream. I believe this is how ProxySQL is doing it, but it's possible the final implementation differs :-)
• v4tk 10y ago
  When you read from non-primary nodes in Group Replication you get stale reads. There is no protection in place.