Re: BUG #16440: pg_basebackup intermittently hangs waiting for input unless run with --checkpoint=fast option

On Fri, May 15, 2020 at 7:49 PM PG Bug reporting form <
noreply(at)postgresql(dot)org> wrote:

> The following bug has been logged on the website:
>
> Bug reference: 16440
> Logged by: Curt Kolovson
> Email address: ckolovson(at)gmail(dot)com
> PostgreSQL version: 10.9
> Operating system: Linux 4.9.219-1.ph2 x86_64 (VMware Photon OS 2.0)
> Description:
>
> We have noticed what appears to be an intermittent bug in pg_basebackup.
> Here is what we are occasionally seeing:
> $ /opt/vmware/vpostgres/current/bin/pg_basebackup -l "repmgr base backup"
> -D /var/vmware/vpostgres/current/pgdata -h 172.18.50.48 -p 5432 -U repmgr
> -X
> stream --verbose --progress
> pg_basebackup: initiating base backup, waiting for checkpoint to complete
>
> And then it hangs indefinitely at this point. It makes no progress (0 CPU),
> so it is hanging on some type of input. Here is ps output:
> postgres 3386 3370 0 15:01 ? 00:00:00
> /opt/vmware/vpostgres/current/bin/pg_basebackup -l repmgr base backup -D
> /var/vmware/vpostgres/current/pgdata -h 172.18.50.48 -p 5432 -U repmgr -X
> stream
>
> We notice that this behavior only occurs intermittently, but when it does,
> it happens repeatedly on that system. The only workarounds we have found
> are
> either to run it with the --checkpoint=fast option, or to restart postgres
> on the primary.
>
> We are using synchronous streaming replication.
>

Define "indefinitely". How long did you wait, and what's the value for your
checkpoint_timeout?

It's perfectly normal for it to be waiting quite some time, as it waits
for the slow speed checkpoint to complete on the server. (And if you want
to look at the processes and status of the server, not the client, to see
what it's doing)

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