Thread: Getting time-dependent load statistics
Hallöchen!
Yesterday I ported a web app to PG. Every 10 minutes, a cron job
scanned the log files of MySQL and generated a plot showing the
queries/sec for the last 24h. (Admittedly queries/sec is not the
holy grail of DB statistics.)
But I still like to have something like this. At the moment I just
do the same with PG's log file, with
log_statement_stats = on
But to generate these plots is costly (e.g. I don't need all the
lines starting with !), and to interpret them is equally costly. Do
you have a suggestion for a better approach?
Tschö,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten.bronger@jabber.rwth-aachen.de
In response to Torsten Bronger <bronger@physik.rwth-aachen.de>: > Hallöchen! > > Yesterday I ported a web app to PG. Every 10 minutes, a cron job > scanned the log files of MySQL and generated a plot showing the > queries/sec for the last 24h. (Admittedly queries/sec is not the > holy grail of DB statistics.) > > But I still like to have something like this. At the moment I just > do the same with PG's log file, with > > log_statement_stats = on > > But to generate these plots is costly (e.g. I don't need all the > lines starting with !), and to interpret them is equally costly. Do > you have a suggestion for a better approach? Turn on stats collection and have a look at the various pg_stat* tables. They'll have stats that you can quickly access with considerably lower overhead. Doing it the way you're doing is driving from Pittsburgh to Maine to get to Ohio. -- Bill Moran http://www.potentialtech.com http://people.collaborativefusion.com/~wmoran/
On Fri, 2009-02-20 at 17:11 +0100, Torsten Bronger wrote: > Hallöchen! > > Yesterday I ported a web app to PG. Every 10 minutes, a cron job > scanned the log files of MySQL and generated a plot showing the > queries/sec for the last 24h. (Admittedly queries/sec is not the > holy grail of DB statistics.) > > But I still like to have something like this. At the moment I just > do the same with PG's log file, with > > log_statement_stats = on > > But to generate these plots is costly (e.g. I don't need all the > lines starting with !), and to interpret them is equally costly. Do > you have a suggestion for a better approach? > Do you want queries, or transactions? If you want transactions you already have that in pg_stat_database. Just do this every 10 minutes: psql -U <user> -d <database> -c "select now() as time,sum(xact_commit) as transactions from pg_stat_Database" Joshua D. Drake > Tschö, > Torsten. > > -- > Torsten Bronger, aquisgrana, europa vetus > Jabber ID: torsten.bronger@jabber.rwth-aachen.de > > -- PostgreSQL - XMPP: jdrake@jabber.postgresql.org Consulting, Development, Support, Training 503-667-4564 - http://www.commandprompt.com/ The PostgreSQL Company, serving since 1997
On Fri, Feb 20, 2009 at 9:11 AM, Torsten Bronger <bronger@physik.rwth-aachen.de> wrote: > Hallöchen! > > Yesterday I ported a web app to PG. Every 10 minutes, a cron job > scanned the log files of MySQL and generated a plot showing the > queries/sec for the last 24h. (Admittedly queries/sec is not the > holy grail of DB statistics.) > > But I still like to have something like this. At the moment I just > do the same with PG's log file, with > > log_statement_stats = on > > But to generate these plots is costly (e.g. I don't need all the > lines starting with !), and to interpret them is equally costly. Do > you have a suggestion for a better approach? You can turn on log duration, which will just log the duration of queries. That's a handy little metric to have and every so often I turn it on and chart average query run times etc with the actual queries. I also turn on logging long running queries of say 5 or 10 seconds or more.
Hallöchen!
Joshua D. Drake writes:
> On Fri, 2009-02-20 at 17:11 +0100, Torsten Bronger wrote:
>
>> Yesterday I ported a web app to PG. Every 10 minutes, a cron job
>> scanned the log files of MySQL and generated a plot showing the
>> queries/sec for the last 24h. (Admittedly queries/sec is not the
>> holy grail of DB statistics.)
>>
>> But I still like to have something like this. [...]
>>
>
> Do you want queries, or transactions? If you want transactions you
> already have that in pg_stat_database. Just do this every 10
> minutes:
>
> psql -U <user> -d <database> -c "select now() as time,sum(xact_commit)
> as transactions from pg_stat_Database"
Well, I'm afraid that transactions are too different from each
other. Currently, I experiment with
SELECT tup_returned + tup_fetched + tup_inserted + tup_updated +
tup_deleted FROM pg_stat_database WHERE datname='chantal';
not being sure whether this makes sense at all. ;-) For exmaple,
does "tup_fetched" imply "tup_returned"?
Tschö,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten.bronger@jabber.rwth-aachen.de
Hallöchen!
Torsten Bronger writes:
> [...] Currently, I experiment with
>
> SELECT tup_returned + tup_fetched + tup_inserted + tup_updated +
> tup_deleted FROM pg_stat_database WHERE datname='chantal';
Stangely, the statistics coming out of it are extremely high. I
just dumped my database with the built-in tool of my web framework
and got approximately 50 times as many row accesses from the command
above as I have objects in my database. The dump routine of my web
framework may do redundant things but not at this extent ...
Tschö,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten.bronger@jabber.rwth-aachen.de