| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WAL Rate Limiting |
| Date: | 2014-01-20 17:41:04 |
| Message-ID: | CA+U5nM+Ljw_j5+BKDpPn8otcLQYN8cy525uKkARLHKR3LxY5_Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 17 January 2014 16:30, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> wrote:
> It occurs to me that this is very similar to the method I proposed in June
> to enforce a hard limit on WAL usage, to avoid PANIC caused by running out
> of disk space when writing WAL:
>
> http://www.postgresql.org/message-id/51B095FE.6050106@vmware.com
>
> Enforcing a global limit needs more book-keeping than rate limiting
> individual sesssions. But I'm hoping that the CHECK_WAL_BUDGET() calls could
> be used for both purposes.
We can't set a useful hard limit on WAL by default without that being
a bigger foot gun than what we have now.
If we did have a limit, I would look to make it less exact and take it
out of the main path for example by checkpointer - or perhaps only
make the check when we switch xlog files.
So I don't want to include that requirement into this current work.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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