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I have a little application that executes select queries against a MySQL cluster.

By using 1 thread to read a record the latency is x.

By using 2 threads to read records concurrently the avg latency is ~ 2x.

By using n threads to read records concurrently the avg latency is ~ nx.

Is there a way to optimize that?

I use one mysqld for 3 Data Nodes.

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  • Make sure that you have uniform servers across the cluster because a slow/overloaded master node can affect performance of the Galera Replication cluster.
  • Check the node status by monitoring value of these variables wsrep_ready and wsrep_connected
  • Make sure that value of this variable is close to 0 wsrep_flow_control_paused
  • A high value for this variable wsrep_local_send_queue_avg for a node indicates a bottleneck in network line, If this is the case, the cause can be at any layer, from physical to OS configuration and must be investigated.
  • You can yourself profile SELECTs on diffrent nodes and see performance.

mysql> SET profiling = 1;

mysql> SELECT * FROM


I hope this information helps.

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Galera Replication cluster and MySQL Cluster (ndbcluster) are two different beasts. – Mindaugas Riauba Dec 19 '13 at 5:35
Oops! Most of the community uses Galera cluster , I could not make out from question? But you can ask to MySQL support regarding this issue – Mahesh Patil Dec 19 '13 at 5:49
@Mahesh Patil, Well, your first point is something I was wondering about, so thanks anyway :) – Wodin Oct 17 '14 at 12:27

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