Comments - Web Applications do not receive all data in Galera Cluster

10 years, 7 months ago Alex yurchenko

Hi, This is a result of Galera synchrony being "virtual". If your application is picky about "stale" data and you want to randomly load-balance connections, you should set wsrep_causal_reads=ON. This will ensure that your application always gets what it has written - at some performance cost. Alternatively you may opt to reread the data if you can determine that it is stale, or use some sort of "sticky" balancing, routing related requests to the same node.

Regards, Alex

 
10 years, 7 months ago Tim Rice

Alex, many thanks for the help. Is it wsrep_causal_reads=1 or wsrep_causal_reads=ON

(or does it really matter)

Is the best way of doing this by modifying the /etc/my.cnf in all the backend sql servers or should I just perform the below sql statement: set global wsrep_causal_reads=1;

I do really appreciate your responses.

 
10 years, 7 months ago Alex yurchenko

I believe 1 and ON are equivalent for boolean variables. This wsrep_causal_reads is a session variable, so you can both set it in my.cnf and/or enable via client - either globally or for the session. In other words enabling it does not require server restart.

 
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