Re: WAL Rate Limiting

On 16 January 2014 17:20, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> Thank you everyone for responding so positively to this proposal. It
> is something many users have complained about.
>
> In time, I think we might want both WAL Rate Limiting and I/O Rate
> Limiting. IMHO I/O rate limiting is harder and so this proposal is
> restricted solely to WAL rate limiting.
>
> I'm comfortable with a session level parameter. I was mulling over a
> wal_rate_limit_scope parameter but I think that is too much.
> I will follow Craig's proposal to define this in terms of MB/s, adding
> that I would calc from beginning of statement to now, so it is
> averaged rate. Setting of zero means unlimited. The rate would be
> per-session (in this release) rather than a globally calculated
> setting.

Parameter renamed to wal_rate_limit.

Not yet modified to produce this in MB/s

> I would like to call it CHECK_FOR_WAL_RATE_LIMIT()

Used CHECK_WAL_BUDGET() as proposed

> That seems like a cheap enough call to allow it to be added in more
> places, so my expanded list of commands touched are
> CLUSTER/VACUUM FULL
> ALTER TABLE (only in phase 3 table rewrite)
> ALTER TABLE SET TABLESPACE
> CREATE INDEX
> which are already there, plus new ones suggested/implied
> COPY
> CREATE TABLE AS SELECT
> INSERT/UPDATE/DELETE

Added, no problems or technical difficulties encountered.

> Please let me know if I missed something (rather than debating what is
> or is not a "maintenance" command).
>
> Any other thoughts before I cut v2 ?

v2 attached

--
Simon Riggs http://www.2ndQuadrant.com/
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