Re: Slave claims requested WAL segment already removed - but it wasn't

On 2 June 2016 at 02:43, Jeff Beck <becked@fastmail.fm> wrote:
> Hi-
> We have a master (pg 9.4.4 on Ubuntu 14.10) and a slave (pg 9.4.8 on
> Centos 7). During a period of heavy use, the slave began complaining
> that the “requested WAL segment xxxxxx has already been removed”. But
> the WAL segment was still on the master. The issue was resolved by
> manually copying the pg_xlog directory over to the slave.
>
> I don’t see any errors on the master log file, or any other messages on
> the slave’s. What happened? How can this be prevented in the future?

I've seen this once. In my case there was a downstream slave of the
slave that I'd forgotten about, and the log entries on the slave were
the result of slave-of-slave asking slave for a WAL file that was not
present on slave.