Big latency in Server version: 5.7.24-26-57 Percona XtraDB Cluster (GPL), Release rel26

MySQL & MariaDB Percona Server for MySQL 5.7
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We are facing in the database Percona XtraDB Cluster that have 5 nodes, a Big latency, that appear when we execute a commande like SHOW DATABASES; or CREATE … it take for so long to give the result even in PREPRODUCTION where there is a little number of databases and no traffic.

Info. We are using Server version: 5.7.24-26-57 Percona XtraDB Cluster (GPL), Release rel26, Revision 65db531, WSREP version 31.33, wsrep_31.33

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Hi Maggi,

PXC is very sensitive to latency, so the more far away the nodes, the more of a performance hit.

Regarding the commands, when executing any DDL, the entire cluster will need to sync to execute the DDL and stop every other DB activity (even for tables not related to the DDL).

So my questions are:
Are all 5 nodes on the same network or are they in different regions/AZ ?
Did you have same issue with other PXC versions with same topology?
Did this behavior (performance hit) started all of a sudden or after some upgrade/ configuration change ?

Regards

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All the nodes are in the same network Vnet (Azure), and in the same region West Europe.
We have only one project that work with PXC, other works with Galera …,
We are facing this bahavior sense month, and now we want to work on it, for your information, we did not do any upgrade or change in the configuration.

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Hello @MAGGI,

that work with PXC, other works with Galera

PXC uses Galera, so those are the same thing. Can you clarify your statement?

Regarding the latency, when you run SHOW DATABASES, what does the processlist look like on other nodes? How many databases do you have? How many tables?

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Yes, PXC uses the libraries of Galera, I mean Galera Cluster that uses MySQL Server + the libraries of Galera.
The process list is having a litle request running with a low time, and we have 5 nodes in the PXC, with more than 50 databases, with a big number of tables.

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This is the same thing as PXC.

  • Percona XtraDB Cluster = Percona MySQL Server + libraries of Galera
  • Galera Cluster = PXC
  • Galera Cluster and PXC are the same thing

With only 50 databases, when you run “SHOW DATABASES” this is slow? I would check all of your memory settings, make sure you are not swapping, benchmark the speed of your disks.

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Yes one I use show databases, it took me so much time to give me the result, it is verry slow.
please I want to know how to do those proposition in Percona:
How can I check the memory seeting ?
How can I know that there is swapping ?
how can benchmark the speed of your disks ?

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Use basic tools like vmstat to see if you are swapping. Use iostat to see how your disks are doing. These are basic system tools.

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