monitoring number of postgresql connections - postgresql

Question

I'd like to monitor on my Zabbix server the number of concurrent PostgreSQL connections, so I've created a cron job that outputs the COUNT of rows on the pg_stat_activity to a file, that will be read by zabbix once a minute.
My problem is that I might have a scenario where I get a COUNT of, say, 10, then have a quick peak of 50 connections, get back to 10, where I do the COUNT again.
In this case the peak would not be noticed.
I've wondered about some counter being inc/dec each connection/disconnection, but failed to think how to do this.
Also I could do the COUNT on a higher frequency and keep an average per minute, but this not solve the problem.
Any thougts in that matter?
Thanks,
Gabriel

Answer 1

Use log files. Here is a quick tutorial for Linux.
1)
Find out where if postgres.conf file located:
postgres=# show config_file;
┌──────────────────────────────────────────┐
│ config_file │
├──────────────────────────────────────────┤
│ /etc/postgresql/9.5/main/postgresql.conf │
└──────────────────────────────────────────┘
2)
Find and edit parameters in it (store the copy somewhere before):
log_connections = on
log_disconnections = on
log_destination = 'csvlog'
logging_collector = on
3)
Restart PostgreSQL:
sudo service postgresql restart
(not sure but probably sudo service postgresql reload will be enough)
4)
Find out where the logs stored:
postgres=# show data_directory; show log_directory;
┌──────────────────────────────┐
│ data_directory │
├──────────────────────────────┤
│ /var/lib/postgresql/9.5/main │
└──────────────────────────────┘
┌───────────────┐
│ log_directory │
├───────────────┤
│ pg_log │
└───────────────┘
5)
Almost done. In files /var/lib/postgresql/9.5/main/pg_log/*.csv you will find records about connections/disconections. It is up to you how to deal with this info.