Re: pg_basebackup error: replication slot "pg_basebackup_2194" already exists

On Tue, May 30, 2017 at 9:14 PM, Ludovic Vaugeois-Pepin <ludovicvp(at)gmail(dot)com
> wrote:

> I ran into the issue described below with 10.0 beta. The error I got is:
>
> pg_basebackup: could not create temporary replication slot
> "pg_basebackup_2194": ERROR: replication slot "pg_basebackup_2194"
> already exists
>
> A race condition? Or maybe I am doing something wrong.
>
>
>
>
>
> Release:
> Name : postgresql10-server
> Version : 10.0
> Release : beta1PGDG.rhel7
>
>
> Test Type:
> Functional testing of a pacemaker resource agent
> (https://github.com/ulodciv/pgha)
>
>
> Test Detail:
> During context/environement setup, pg_basebackup is invoked (in
> parallel) from multiple virtual machines. The backups are then started
> as asynchronously replicated hot standbies.
>
>
> Platform:
> Centos 7.3
>
>
> Installation Method:
> yum -y install
> https://download.postgresql.org/pub/repos/yum/testing/10/
> redhat/rhel-7-x86_64/pgdg-redhat10-10-1.noarch.rpm
> yum -y install postgresql10-server postgresql10-contrib
>
>
> Platform Detail:
>
>
> Test Procedure:
>
> Have pg_basebackup run simultaneously on multiple hosts against
> the same instance eg:
>
> pg_basebackup -h test4 -p 5432 -D /var/lib/pgsql/10/data -U repl1
> -Xs
>
>
> Failure?
>
> E deploylib.deployer_error.DeployerError:
> postgres(at)test5: got exit status 1 for:
> E pg_basebackup -h test4 -p 5432 -D
> /var/lib/pgsql/10/data -U repl1 -Xs
> E stderr: pg_basebackup: could not create temporary
> replication slot "pg_basebackup_2194": ERROR: replication slot
> "pg_basebackup_2194" already exists
> E pg_basebackup: child process exited with error 1
> E pg_basebackup: removing data directory
> "/var/lib/pgsql/10/data"
>
>
> Test Results:
>
>
> Comments:
> This seems to be new with 10. I recently began testing the
> pacemaker resource agent against PG 10. I never had (or noticed) this
> failure with 9.6.1 and 9.6.2.
>

Hah, that's an interesting failure. In the name of the slot, the 2194 comes
from the pid -- but it's the pid of pg_basebackup.

I assume you're not running the two pg_basebackup processes on the same
machine? Is it predictable when this happens (meaning that the pid value is
actually predictable), or do you have to run it a large numbe rof times
before it happens?

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>