Hi all,
I am continuing to investigate and I found a probable malfunctioning in
linux semaphores: I foud postgres semaphores are deleted during barman
backup process. To executing test I have created a new empty postgres
cluster in a Debian Citrix virtual machine; this is output of ipcs -s
command:
Before start backup
postgres@postgres-1:/opt/postgres/pgclusters/barman_test/pg_log$ ipcs -s
------ Semaphore Arrays --------
key semid owner perms nsems
0x005b81c9 8912896 postgres 600 17
0x005b81ca 8945665 postgres 600 17
0x005b81cb 8978434 postgres 600 17
0x005b81cc 9011203 postgres 600 17
0x005b81cd 9043972 postgres 600 17
0x005b81ce 9076741 postgres 600 17
0x005b81cf 9109510 postgres 600 17
0x005b81d0 9142279 postgres 600 17
During backup
------ Semaphore Arrays --------
key semid owner perms nsems
After end of barman backup command
postgres@postgres-1:/opt/postgres/pgclusters/barman_test/pg_log$ ipcs -s
------ Semaphore Arrays --------
key semid owner perms nsems
0x005b81c9 9175040 postgres 600 17
0x005b81ca 9207809 postgres 600 17
0x005b81cb 9240578 postgres 600 17
0x005b81cc 9273347 postgres 600 17
0x005b81cd 9306116 postgres 600 17
0x005b81ce 9338885 postgres 600 17
0x005b81cf 9371654 postgres 600 17
0x005b81d0 9404423 postgres 600 17
The linux kernel version is 3.16.0-4-amd64
I have executed the same test with a database regularly backupped with
barman with the same version of postgres (9.4.4) and the semaphores are the
same before, during and after backup command execution. However in this case
the linux kernel version is 2.6.38.2-grsec-xxxx-grs-ipv6-64.
Do you think this semaphores anomaly can cause backup issue?
Do you have any suggestions to resolve it?
Thanks in advance.
Alessio
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