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From:Magnus Blåudd Date:April 17 2013 11:37am
Subject:Re: Threads_connected
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On 04/15/2013 02:45 PM, Raymond Peachey wrote:
> Hello,
> Is it possible to actually monitor number of connected clients on your
> mysql cluster when you have cluster connection pooling enabled?
> For example, in our case we have a MySQL Cluster node with 32 cores, which
> we've allocated 30 to use ndb connection pooling. When running a mysqlslap
> with a concurrency of, say, 60, I do not see that value show in
> threads_connected. Nor, do I see it show processlist.
> When I remove the ndb connection pooling, I accurately see the processlist
> showing all connected clients. I assume this is because of how the ndb
> connection pooling, in essence (correct me if I'm wrong), a mysqld child
> process that is used to connect to the cluster, which maybe is retaining
> it's own counters?? Is my thinking correct here, or is there a documented,
> alternate way of monitoring connected clients when using ndb connection
> pooling?
> Thanks,
> -Ray

The option --ndb-cluster-connection-pool controls how many connections 
the MySQL Server uses when talking to the NDB data nodes. I.e like the 
manual says "mimicking several MySQL Servers"

This should not affect how many connections or threads your client 
application(for example mysqlslap) uses when connecting to the MySQL Server.

Neither can I imagine that the values of threads_connected in any way is 
connected to the above configuration variable.

Show some queries and the exact values used..

Btw. I think that 30 is a high value... maybe too high? Check the MySQL 
Server log file for error messages while starting up and connecting to 
the cluster.

/ Magnus
Threads_connectedRaymond Peachey15 Apr
  • Re: Threads_connectedMagnus Blåudd17 Apr
    • Re: Threads_connectedRaymond Peachey17 Apr