Re: Replication failed after stalling

Joe Van Dyk <joe@tanga.com> writes:

> I'm running Postgresql 9.3. I have a streaming replication server. Someone was running a long COPY query (8 hours) on
thestandby which halted replication. The 
> replication stopped at 3:30 am. I canceled the long-running query at 9:30 am and replication data started catching
up.
>
> The data up until 10 am got restored fine (took until 10:30 am to restore that much). Then I started getting errors
like"FATAL:  could not receive data from WAL 
> stream: ERROR:  requested WAL segment 00000001000003C300000086 has already been removed".
>
> I'm confused about how pg could restore data from 3:30 am to 10 am, then start complaining about missing WAL files.
>
> What's the best way to avoid this problem? Increase wal_keep_segments?

Yes and/or implement as a hybrid of streaming and WAL shipping.

Quite simply, your wal_keep segments was almost enough to  get you
through that backlog period but as your standby was catching up, it hit
a point  where  there was a gap.

Depending on how much traffic your master sees at various times of the
day, it's unsurprising that during peak loads, your grace-period is a
lot lower than during off-peak times due to variations in how quickly
WAL segments are filled and cycled over.

HTH

>
> Joe
>

--
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net
p: 312.241.7800