[pgpool-general: 8178] Re: Unable to acquire JDBC Connection

Nikola(HM) nikm71 at hotmail.com
Wed May 25 18:22:13 JST 2022


Thank you for response.

We run 3 replicas of Pgpool in k8s.


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.


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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