[pgpool-general: 8474] failed to lock semaphore

[Steeve Boulanger]

Greetings,

I've been working at implementing pgPool recently, and got everything
working fine for the most part, but I keep seeing some WARNING messages in
pgpool.log, and was wondering if anyone knows how to fix this:

2022-10-26 23:58:02.103: sr_check_worker pid 765970: WARNING:  failed to
lock semaphore
2022-10-26 23:58:02.103: sr_check_worker pid 765970: DETAIL:  Invalid
argument
2022-10-26 23:58:02.103: sr_check_worker pid 765970: WARNING:  failed to
unlock semaphore
2022-10-26 23:58:02.103: sr_check_worker pid 765970: DETAIL:  Invalid
argument

These warnings appear in the pgpool.log file. but also when making a client
connection, such as:

postgres at psql-01:~$ psql -h spsql-vip -p 5432 -U postgres -c "select now(),
count(*) from pg_stat_activity;"
WARNING:  XX000: failed to lock semaphore
DETAIL:  Invalid argument
LOCATION:  pool_sema.c:129
WARNING:  XX000: failed to unlock semaphore
DETAIL:  Invalid argument
LOCATION:  pool_sema.c:202
<..>
              now              | count
-------------------------------+-------
 2022-10-26 23:22:57.193342+00 |   276
(1 row)

My environment is as follow:

# lsb_release -a
==
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.5 LTS
Release:        20.04
Codename:       focal
==

# apt list --installed | grep pgpool
==
libpgpool2/focal-pgdg,now 4.3.3-1.pgdg20.04+1 amd64 [installed]
pgpool2/focal-pgdg,now 4.3.3-1.pgdg20.04+1 amd64 [installed]
postgresql-13-pgpool2/focal-pgdg,now 4.3.3-1.pgdg20.04+1 amd64 [installed]
==

# pgpool --version
pgpool-II version 4.3.3 (tamahomeboshi)

$ postgres --version
postgres (PostgreSQL) 13.8 (Ubuntu 13.8-1.pgdg20.04+1)

And lastly, in case it can help. here's a strace snippet which is related
to this error I believe:

semtimedop(1, [{7, -1, SEM_UNDO}], 1, NULL) = -1 EINVAL (Invalid argument)
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
write(2, "\0\0\245\0NI\0\0t2022-10-27 13:06:21.879"..., 174) = 174
semtimedop(1, [{7, 1, SEM_UNDO}], 1, NULL) = -1 EINVAL (Invalid argument)
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
write(2, "\0\0\247\0NI\0\0t2022-10-27 13:06:21.879"..., 176) = 176

I tried to google for this issue, and search the mailing list, but to
no avail. Any tips on how to fix this would be greatly appreciated!

Regards,
Steeve
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