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Cluster hangs, too many connections. Processes in 'wsrep in pre-commit stage' state.

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  • Cluster hangs, too many connections. Processes in 'wsrep in pre-commit stage' state.

    Hi,

    I am running 5.6.15-56-log Percona XtraDB Cluster (GPL), Release 25.5, Revision 759, wsrep_25.5.r4061 on Fedora 20. I have three nodes within the cluster happily doing their thing for the most part yet when we start experiencing high traffic the cluster will start locking up.

    The connection limit will be reached quickly with most processes in the list showing 'wsrep in pre-commit stage'. The queries are all INSERT and UPDATE on the same table (which has a primary key).

    The logs don't show anything of interest other than '[Warning] Too many connections'.

    I have set the gcs.fc_limit to 1000 which has helped reduce the number of times the cluster locks, however I cannot eliminate the problem completely.

    Other threads have suggested checking:

    SHOW STATUS LIKE 'Threads%'; and

    SELECT substring_index(host, ':',1) AS host_name,state,count(*) FROM information_schema.processlist GROUP BY state,host_name; Unfortunately I haven't been able to execute them while the problem is occurring yet.

    Before the cluster we had a Master-Slave setup in place rather than Master-Master. If this problem cannot be addressed is there an easy way to revert to a Master-Slave setup?

    Thanks.
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