Help for max_connections

[marcio]

Hello !

Please, help me for the correct understanding:

I have a loadbalancer (HAPROXY) and more 3 nodes with XtraDBCluster 5.7.23 (Centos 7), each node configured with max_connections = 350.

The correct is:

a) each node accept 350 max connections and whole cluster may accept 1050 (3x350) connections ??

or

b) each node accept 350 max connections and whole cluster will accept 350 connections too ??

Thank you.

[marcio]

Nothing about it friends ?! :(

[przemek]

Hello Marcio,

HaProxy will redirect client connections to one of the backend nodes, depending on configuration. If all nodes are configured equally (round robin), yes, the cluster may accept total around 3 x max_connections. But I’d expect at least some uneven traffic distribution and effectively it may be bit less.
Remember that proxy node may need some TCP stack tuning when dealing with large number of total connections.

Btw, completely different situation is with ProxySQL, which is more then just regular proxy, and has it’s own connection pool. Thanks to multiplexing, it can actually accept many times more connections then total max_connection all backends offer.

[marcio]

Thanks przemek !!!