[pgpool-hackers: 677] Re: Logging load balancing result

Muhammad Usama m.usama at gmail.com
Sat Nov 22 00:12:19 JST 2014


Hi

I think this is a very good idea, and a much needed feature. As load
balancing is one of the prime feature of the pgpool-II and getting
these stats will be very helpful and informative.

Although I think having the ability to reset stats should also be
included as the part of this feature and it would be nice to add a
pool_ command to check the stats reset time.


Kind regards,
Muhammad Usama

On Fri, Nov 21, 2014 at 5:07 AM, Tatsuo Ishii <ishii at postgresql.org> wrote:
> Hi,
>
> We are frequently asked a way to know how SELECTs are load balanced
> among database nodes. For now there are two ways:
>
> 1) enable log_per_node_statement and grep pgpool.log
>
> 2) enable log_statement and grep PostgreSQL log
>
> Both increase log volume and are needed to create scripts or set up
> external monitoring tools such as zabbix. Also I feel #1 and #2 are
> overkill for those who just want to know number of SELECTs load
> balanced and are not interested in individual SELECT statement.
>
> So I would like to propose to add new functionality to allow to gather
> load balancing statistics. The result will be shown using "show
> pool_nodes" command in a new column "lbs_stat".
>
> => show pool_nodes;
>  node_id | hostname | port  | status | lb_weight |  role   | lbs_stat
> ---------+----------+-------+--------+-----------+---------+---------
>  0       | /tmp     | 11000 | 2      | 0.333333  | primary | 12345
>  1       | /tmp     | 11001 | 2      | 0.333333  | standby | 45678
>  2       | /tmp     | 11002 | 2      | 0.333333  | standby | 56789
>
> Here lbs_stat indicates how many SELECTs are load balanced to each node.
>
> The load balancing statistics are accumulated in a shared memory area
> and will have quite little overhead. So I feel there's no need to the
> functionality turned off.
>
> Comments and suggestions are welcome.
>
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
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