Re: Streaming replication and WAL archive interactions

12 дек. 2014 г., в 16:46, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> написал(а):

> There have been a few threads on the behavior of WAL archiving, after a standby server is promoted [1] [2]. In short, it doesn't work as you might expect. The standby will start archiving after it's promoted, but it will not archive files that were replicated from the old master via streaming replication. If those files were not already archived in the master before the promotion, they are not archived at all. That's not good if you wanted to restore from a base backup + the WAL archive later.
>
> The basic setup is a master server, a standby, a WAL archive that's shared by both, and streaming replication between the master and standby. This should be a very common setup in the field, so how are people doing it in practice? Just live with the wisk that you might miss some files in the archive if you promote? Don't even realize there's a problem? Something else?

Yes, I do live like that (with streaming replication and shared archive between master and replicas) and don’t even realize there’s a problem :( And I think I’m not the only one. Maybe at least a note should be added to the documentation?

>
> And how would we like it to work?
>
> There was some discussion in August on enabling WAL archiving in the standby, always [3]. That's a related idea, but it assumes that you have a separate archive in the master and the standby. The problem at promotion happens when you have a shared archive between the master and standby.

AFAIK most people use the scheme with shared archive.

>
> [1] http://www.postgresql.org/message-id/CAHGQGwHVYqbX=A+zo+AvFbVHLGoypO9G_QDKbabeXgXBVGd05g@mail.gmail.com
>
> [2] http://www.postgresql.org/message-id/20140904175036.310c6466@erg
>
> [3] http://www.postgresql.org/message-id/CAHGQGwHNMs-syU=MEVSESTHna+Exd9pfO_OHHFPJCwOVaYRZKw@mail.gmail.com.
>
> - Heikki
>
>
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Vladimir