From: Nagy László Zsolt <gandalf@shopzeus.com>
To: pgsql-admin@lists.postgresql.org
Subject: Re: Reliable WAL file shipping over unreliable network
Date: Wed, 28 Feb 2018 16:46:42 +0100
Message-ID: <debd4205-e27a-cd9d-9169-6748e65083a2@shopzeus.com> (raw)
In-Reply-To: <ee3ae4be-ab24-8443-82c1-95bcd4f86a63@shopzeus.com>
References: <dd116172-3ddf-ee56-57f3-6e18d49abf8e@shopzeus.com>
<400AC9CD-1E43-422C-A689-70BDBAFF231E@elevated-dev.com>
<ee3ae4be-ab24-8443-82c1-95bcd4f86a63@shopzeus.com>
>>> Is there a utility that is widely used for WAL file shipping, and
>>> addresses these problems?
>> rsync
> Should I use rsync with --remove-source-files option? Will that solve
> all problems with unreliable networks?
Another problem with rsync might be that it does not know if a WAL file
on the source side is growing (e.g. being written) and it might start
copy that before it is fully flushed to disk. I see this as a big
problem, but I don't have experience.
My first idea to address this is to execute an archive command something
like this:
test ! -f /pg_wal/%f && cp %p /volume/pg_wal_tmp/%f && mv
/volume/pg_wal_tmp/%f /volume/pg_wal/%f
E.g. move the file into the archive dir only after it has been fully
copied to the destination volume. But then we still have the problem of
partially written files on the slave side.
I can come up with other ideas, but I do not want to reinvent the wheel.
Can somebody please tell me how to deal with partially written WAL files?
Thanks,
Laszlo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-admin@postgresql.org
Cc: gandalf@shopzeus.com, pgsql-admin@lists.postgresql.org
Subject: Re: Reliable WAL file shipping over unreliable network
In-Reply-To: <debd4205-e27a-cd9d-9169-6748e65083a2@shopzeus.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox