[pgpool-general: 4374] Re: Pgpool - connection hangs in DISCARD ALL

[Gerhard Wiesinger]

On 28.01.2016 01:10, Tatsuo Ishii wrote:
>> On 21.01.2016 20:52, Muhammad Usama wrote:
>>> Hi
>>>
>>> I am looking into this issue. and unfortunately like Ishii-San I am
>>> also not able to reproduce it. But I found one issue in 3.4 that might
>>> cause the problem. Can you please try the attached patch if it solves
>>> the problem. Also, if the problem still persists, it would be really
>>> helpful if you could share the pgpool-II log.
>>>
>> I looked at the patch but it includes only logging changes and no
>> functional changes. Therefore I didn't test it. Do you expect and
>> behavioral changes to fix it, and why?
> elog() is not only a logging function, but also it plays very
> important role including exception handling and error treatments in
> pgpool-II. If you are familiar with PostgreSQL internals, you may
> notice it (elog() was imported from PostgreSQL source tree).

Tried version 3.5.0 where the patch is included. Still not working. See 
backtrace below.

Reverting to 3.3.7 which works perfectly.

Ciao,
Gerhard

(gdb) back
#0  0x00007fd87fdb6d43 in __select_nocancel () from /lib64/libc.so.6
#1  0x0000564471af16a1 in pool_check_fd (cp=cp at entry=0x564473dfa610) at 
protocol/pool_process_query.c:635
#2  0x0000564471af1976 in pool_check_fd (cp=cp at entry=0x564473dfa610) at 
protocol/pool_process_query.c:657
#3  0x0000564471b1f67b in pool_read (cp=0x564473dfa610, 
buf=buf at entry=0x7ffc1d71bf97, len=len at entry=1) at utils/pool_stream.c:162
#4  0x0000564471af8e6e in read_kind_from_backend 
(frontend=frontend at entry=0x564473df3e60, 
backend=backend at entry=0x564473df2e00,
     decided_kind=decided_kind at entry=0x7ffc1d71c397 "E") at 
protocol/pool_process_query.c:3234
#5  0x0000564471affdc9 in ProcessBackendResponse 
(frontend=frontend at entry=0x564473df3e60, 
backend=backend at entry=0x564473df2e00, state=state at entry=0x7ffc1d71c41c,
     num_fields=num_fields at entry=0x7ffc1d71c41a) at 
protocol/pool_proto_modules.c:2356
#6  0x0000564471af5b15 in pool_process_query (frontend=0x564473df3e60, 
backend=0x564473df2e00, reset_request=reset_request at entry=1) at 
protocol/pool_process_query.c:302
#7  0x0000564471aed98c in backend_cleanup (backend=<optimized out>, 
frontend_invalid=frontend_invalid at entry=0 '\000', 
frontend=0x564471e09e40 <child_frontend>)
     at protocol/child.c:437
#8  0x0000564471af0637 in do_child (fds=fds at entry=0x564473dee030) at 
protocol/child.c:234
#9  0x0000564471ace107 in fork_a_child (fds=0x564473dee030, id=8) at 
main/pgpool_main.c:678
#10 0x0000564471aceb6d in reaper () at main/pgpool_main.c:2254
#11 0x0000564471ad322b in PgpoolMain (discard_status=<optimized out>, 
clear_memcache_oidmaps=<optimized out>) at main/pgpool_main.c:429
#12 0x0000564471acc7b1 in main (argc=<optimized out>, 
argv=0x7ffc1d7219e8) at main/main.c:310

#1  0x0000564471af16a1 in pool_check_fd (cp=cp at entry=0x564473dfa610) at 
protocol/pool_process_query.c:635
635                     fds = select(fd+1, &readmask, NULL, &exceptmask, 
timeoutp);

(gdb) print fd
$1 = 8
(gdb) print readmask
$2 = {fds_bits = {256, 0 <repeats 15 times>}}
(gdb) print exceptmask
$3 = {fds_bits = {256, 0 <repeats 15 times>}}
(gdb) print timeoutp
$4 = (struct timeval *) 0x0