From: Josh Berkus <josh@agliodbs.com>
To: pgsql-hackers@postgresql.org
Subject: Re: Simplifying replication
Date: Fri, 22 Oct 2010 10:34:07 -0700
Message-ID: <4CC1CB0F.7050006@agliodbs.com> (raw)
In-Reply-To: <26273.1287768288@sss.pgh.pa.us>
References: <201010220058.o9M0waa06053@momjian.us>
<4CC0E465.4000700@agliodbs.com>
<AANLkTineXrnRAkRV4Cs=rmSo0QkWkFRVYQpj0AWXGn2=@mail.gmail.com>
<4CC0F10D.3000201@agliodbs.com>
<AANLkTi=Nz06NGkUAEzJ7r=CMRsiUAJXRsWALqw-jZ62A@mail.gmail.com>
<4CC1C74E.8080409@agliodbs.com>
<26273.1287768288@sss.pgh.pa.us>
>> max_wal_size
>> min_wal_size
>
> [ scratches head... ] What's the functional effect of min_wal_size, exactly?
Replaces wal_keep_segments. The rename is to make the GUCs obviously
symmetrical, and to make it clear that the *meaning* of the variable has
changed.
>> Even better would be to replace min_wal_size with min_wal_time, which
>> would set a time span for the oldest WAL segment to be kept (up to
>> max_wal_size - 2). Hmmm. That doesn't seem that hard to implement.
>> Is it?
>
> Um, what happens when honoring min_wal_time conflicts with honoring
> max_wal_size?
When we get close enough to max_wal_size (we'll need a couple segments
of leeway, I think), we start recycling WAL segments even if they are
less that min_wal_time old. This is under the presumption that most
DBAs will prefer having the standby desyncrhonize to having the master
lock up due to running out of disk space. Presumably if such recycling
happens we'd also write a WARNING to the logs.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
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-hackers@postgresql.org
Cc: josh@agliodbs.com
Subject: Re: Simplifying replication
In-Reply-To: <4CC1CB0F.7050006@agliodbs.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