[pgpool-general: 5651] Re: oom when memory_cache_enabled is on

[Pavel]

Yes,  of course. I wrongly put an equal sign between number of selects
and number of connections. Sorry.
Our testing software reconnects, but not as often.

You wrote 28 июля 2017 г., 2:05:37:

> To fire child_max_connections, your client needs to reconnect to
> Pgpool-II. Just sending many selects does not trigger it.

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

>> I've  tried  to force pgpool to restart its child processes by setting
>> really low numbers in child_max_connections, for example
>> child_max_connections = 10
>> but   still   even   after   serving   more  than  200k  selects  with
>> max_init_children  =  500    all  pgpool child processes' pids are the
>> same as they were right after pgpool start.
>> 
>> Does  it  mean that pgpool didn't restart any of its childs or is this
>> an  expected  behaviour and child's pid is not supposed to change when
>> pgpool restarts its child process?
>> 
>> 
>>> Hello.
>> 
>>> We started testing our project under heavy load and encountered out of
>>> memory  condition  if pgpool is running with memory_cache_enabled=on, both
>>> with shmem and memcached.
>> 
>>> Under simulated heavy load pgpool consumes all available memory (16Gb)
>>> in just a few minutes and then kernel kills it.
>> 
>>> I've found this old similar bug thread:
>>> http://www.pgpool.net/mantisbt/view.php?id=52
>>> and  tried  running  pgpool  with  valgrind,  but (perhaps due to high
>>> number  of pgpool childs?) system was almost unresponsive and i had to
>>> restart pgpool without valgrind.
>> 
>>> I'm  attaching pgpool log which was written during the short period of
>>> valgrind activity.
>>> There  are some records, but I have zero experience in this area and I
>>> have  no  idea  if  they  are  indicating a problem or not. One of the
>>> records:
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==    at
>>> 0x4C2DB8F: malloc (in
>>> /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==    by
>>> 0x448063: save_ps_display_args (ps_status.c:173)
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==    by 0x407F41: main (main.c:192)
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612== LEAK SUMMARY:
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==   
>>> definitely lost: 96 bytes in 1 blocks
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==   
>>> indirectly lost: 343 bytes in 11 blocks
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==     
>>> possibly lost: 0 bytes in 0 blocks
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==    still
>>> reachable: 254,475 bytes in 3,102 blocks
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==         suppressed: 0 bytes in 0 blocks
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612== Reachable
>>> blocks (those to which a pointer was found) are not shown.
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612== To see
>>> them, rerun with: --leak-check=full --show-leak-kinds=all
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612==
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612== For counts
>>> of detected and suppressed errors, rerun with: -v
>>> Jul 26 09:27:59 ip-172-31-26-132 pgpool2[3707]: ==4612== ERROR
>>> SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
>> 
>> 
>> 
>>> "ulimit  -a"  output  of  user  postgres (pgpool is running under this
>>> account):
>>> postgres at ip-172-31-26-132:~$ ulimit -a
>>> core file size          (blocks, -c) 0
>>> data seg size           (kbytes, -d) unlimited
>>> scheduling priority             (-e) 0
>>> file size               (blocks, -f) unlimited
>>> pending signals                 (-i) 64124
>>> max locked memory       (kbytes, -l) 64
>>> max memory size         (kbytes, -m) unlimited
>>> open files                      (-n) 10000
>>> pipe size            (512 bytes, -p) 8
>>> POSIX message queues     (bytes, -q) 819200
>>> real-time priority              (-r) 0
>>> stack size              (kbytes, -s) 8192
>>> cpu time               (seconds, -t) unlimited
>>> max user processes              (-u) 64124
>>> virtual memory          (kbytes, -v) unlimited
>>> file locks                      (-x) unlimited
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> -- 
>> Best regards,
>>  Pavel                          mailto:balroga3 at yandex.ru
>> 
>> _______________________________________________
>> pgpool-general mailing list
>> pgpool-general at pgpool.net
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-- 
Best regards,
 Pavel                          mailto:balroga3 at yandex.ru