[pgpool-general: 5642] Re: oom when memory_cache_enabled is on

[Pavel]

Sorry, forgot to mention pgpool version.
I'm using 3.6.5 compiled from source on ubuntu 14.04


> 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