pgsql and net-snmp

Hello,

**** I really should ask if i am mailing to the correct mailing list in
regarding the question i will ask.
**** But ...

I am working for a small company offering IT services.
We are in the acceptance stage for a migration of an old UNIX app
managing a huge load of data.

This acceptance environment is using a VMWARE ESX platform, a jboss as
application server ( java servlet as client application )
and a pgsql database. As the developpers knew there will be a lot of data,
the server specs are quite high...
( on RAM space for instance... jboss + pgsql on the same server ).

As it is ... this environement gets poor results ...

This could be a lot of things and as i am charged of the applications
monitoring....

How-to monitor pgsql ?
( considering the server's general statistics and events are already covered
:
cpu usage, memory usage, shutdown and reboot events, unplanned down time )

- i have got a net-snmp at service
- i have got an event listener too ( traplistener + event-rules)

After looking through the pgsql manual and google ...
- i want base info on the pgsql processes: cpu usage, memory usage and so
on...
- i want base healthiness information on the database

lets get to pgsql...

- base processes information:
-------------------------------------
As i have understood it pgsql runs as as a single process and forks itself
for each clients that connects to the database.
As i have seen the number of starting processes is set into pgsql.
( when there is no connection to the server i see six process postgres in
idle mode )
The pgsql client processes names are giving informations on themselves:

using egrep and ps:
#ps aux | egrep ".*postgres: .* .*:ffff:.*\..*\..*\..*:.*"
returns a list of pgsqlclient processes

net-snmp ?
as i look into monitoring pgsql client processes i have written a
shell/awk script returning little data on those.
#./pgsql.cli.mon
$ [ number of processes ]
$ [ min cpu usage % ]
$ [ average cpu usage % ]
$ [ max cpu usage % ]
$ [ min mem usage % ]
$ [ average mem usage % ]
$ [ max mem usage % ]
$ [ min virtual mem ]
$ [ average virtual mem ]
$ [ max virtual mem ]
$ [ min real mem ]
$ [ average real mem ]
$ [ max real mem ]
and by feeding it into snmpd.conf (exec statement) i get those data
through snmp

The maximum and minimum number of processes allowed are already managed by
the net-snmp base agent.

*** That is a real tiny base for some performance testing.
*** The script should be rewritten in an other language ( perl ):
*** making sums and averages of doubles in shell lead me ( as too
often... ) use pipes and awk....

- database healthiness ?
------------------------------
For that part i have only google'd and looked into the pgsql manual ( and
extracted a "SELECT * from pg_stats" from pgsql ).
I could use an extraction script that maps selected data into snmp ( as a
have done for the processes informations ).
But using such a way to pack pgsql's pg_stats into snmp will include regular
query to this table.

Is there any performance issues generated by this type of monitoring ?

As i have not found any pgsql monitoring agent using snmp (yet) , i am
trying to gather any data concerning pgsql and feed it to snmp.
But i always feel like i have not looked enough for anything.

Is there any snmp agent, for pgsql ? If i gather statistics from pg_stats,
is there any values/properties, specific to pgsql that i should look into ?