[pgpool-general: 8181] Re: Unable to acquire JDBC Connection
pengbo at sraoss.co.jp
Thu May 26 12:02:05 JST 2022
> Thank you for response.
> We run 3 replicas of Pgpool in k8s.
> NUM_INIT_CHILDREN=400, MAX_POOL=2, LISTEN_BACKLOG_MULTIPLIER=2
> On PostgreSQL max_connections=2500 . We set very big value here now to
> test only pgpool for a lack of connection.
> When load is running max number of connections to PostgreSQL is slightly
> over 200 (i.e. 212, 220). At that time command "SHOW POOL_PROCESSES" on
> Pgpool shows many idle processes.
> And if I understand correctly, if cause of the error "Unable to acquire
> JDBC Connection" was in lack of connections, Pgpool would issue an error
> message about that.
By default, Pgpool-II doesn't return an error message.
By default, Pgpool-II accepts up to num_init_children connection requests and
queues up more connection requests until one of child process becomes free.
If you set reserved_connections parameter, Pgpool-II will return an error message
"Sorry, too many clients already" if the limit is reached.
reserved_connections = 1
> On 25.05.2022 09:15, Bo Peng wrote:
> > Hello,
> >> Hello,
> >> Our application use Pgpool in k8s with docker image pgpool/pgpool2, and
> >> our PostgreSQL nodes are on virtual machines.
> >> When we tried to perform load test our application, we have received a
> >> lot of errors of application services that connect to database through
> >> Pgpool:
> >> "Could not open JPA EntityManager for transaction; nested exception is
> >> org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC
> >> Connection"
> >> If application connects to database directly without Pgpool, this error
> >> does not appear.
> > The setting of num_init_children may cause this error.
> > Could you run ps command and check if there are processes in the "wait for connection request" status?
> > How many Pgopol-II replicas do you configured?
> > What are the values of num_init_children, max_pool and PostgreSQL's max_connections.
> >> Do you have any experience with such problem and could you tell why it
> >> occurs, i.e. why the service can't connect Pgpool and how to fix it?
> >> Thanks in advance.
> >> --
> >> Regards,
> >> Nikola
> >> _______________________________________________
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> >> pgpool-general at pgpool.net
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Bo Peng <pengbo at sraoss.co.jp>
SRA OSS, Inc. Japan
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