[pgpool-general: 8008] Re: connection is not available

Tatsuo Ishii ishii at sraoss.co.jp
Sun Jan 30 19:10:24 JST 2022


> Hello,
> 
> There are no additional errors on pgpool when that exceptions appears.
> 
> We tested by Jmeter tool.
> 
> It was configured for send read requests to service that connected to
> pgpool.
> 
> The requests was sent as 300 Threads within 100 second Ramp-up period
> (time that takes to start all the threads))
> 
> I don’t think it makes sense to tell which requests in detail, since
> they are specific to our service.
> 
> Because not all child processes of Pgpool was busy during load
> testing. We set 200 child processes and 30% of the processes was free.

How do you define child processes of Pgpool was busy or free?

If a child processes of Pgpool is occupied by a client session, then
other client cannot connect to the child process of Pgpool until the
client disconnects to the process. It's not irrevelant whether the
process is actually doing something or not.

If you are using the latest Pgpool-II version (4.3.x), pcp_proc_info
command can tell you whether each child process is occupied by client
session. If it's other than "wait for connection request" then it's
occupied. See the manual for details.

If you are using pre 4.3, you can use ps command to the each process
status.

> It looks like Pgpool sometimes doesn't keep up to serve new connection
> request for some reason. Is it possible? What are the likely reasons
> for this?

I guess you have to increase num_init_children to more than 300 since
your test generates 300 connections.

Best reagards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

> Regards,
> Nikolay
> 
> On 25.01.2022 06:11, Bo Peng wrote:
>> Hello,
>>
>> On Mon, 24 Jan 2022 18:22:12 +0200
>> "Nikolay Mastilo (HM)" <nikm71 at hotmail.com> wrote:
>>
>>> Hello,
>>>
>>> In our environment we received the error of our service that connects
>>> to Pgpool:
>>>
>>> "HikariPool-1 - Connection is not available, request timed out after
>>> 30012ms."
>>>
>>> We run load test that generate 300 connections that send requests to
>>> database each 1-4 sec via Pgpool.
>>>
>>> Most of connections was successed. But 3-4% was failed and service
>>> produced exception log which I mentioned above.
>>>
>>> num_init_children = 200
>>>
>>> max_pool = 4
>>>
>>> I will be appreciate any idea what's going on.
>> Thank you for reporting this issue.
>>
>> Is there any error in pgpool logs?
>>
>> It would be appreciated if you could share the load test scenario
>> to help us to reproduce this issue.
>>
>>
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