Re: [HACKERS] Proposal: pg_rewind to skip config files

On Tue, Sep 5, 2017 at 7:54 PM, Vladimir Borodin <root@simply.name> wrote:
> 5 сент. 2017 г., в 12:31, Chris Travers <chris.travers@adjust.com>
> написал(а):
>
> I think the simplest solution for now is to skip any files ending in .conf,
> .log, and serverlog.

This is not a portable solution. Users can include configuration files
with the names they want. So the current patch as proposed is
definitely not something worth it.

> For example, in archive_command we put WALs for archiving from
> pg_xlog/pg_wal into another directory inside PGDATA and than another cron
> task makes real archiving. This directory ideally should be skipped by
> pg_rewind, but it would not be handled by proposed change.

I would be curious to follow the reasoning for such a two-phase
archiving (You basically want to push it in two places, no? But why
not just use pg_receivexlog then?). This is complicated to handle from
the point of view of availability and backup reliability + durability.

> While it is definitely an awful idea the user can easily put something
> strange (i.e. logs) to any important directory in PGDATA (i.e. into base or
> pg_wal). Or how for example pg_replslot should be handled (I asked about it
> a couple of years ago [1])? It seems that a glob/regexp for things to skip
> is a more universal solution.
>
> [1]
> https://www.postgresql.org/message-id/flat/8DDCCC9D-450D-4CA2-8CF6-40B382F1F699%40simply.name

Well, keeping the code simple is not always a bad thing. Logs are an
example that can be easily countered, as well as archives in your
case.
--
Michael