The problem

Suddenly I had to update one nagios server from 3.x to 4.x.

After the update there was some strange condition, when we had more then 100 services in a Warning/Critical state, Nagstamon or Nagios Checker were unable to show certain alerts.

 

It turned out that by default Nagios 4.0 split Warning/Critical results by pages if they are more then 100. This leads to Nagstamon/Nagios Checker mallfunction, as they are only able to show the first page of 100 services.

Versions of Nagstamon above 0.9.11 seem to work right with this.

The fix

You can deal with Nagstamon by updating it to the latest version, but you can’t do anything about “Nagios checker” browser plugin.

That’s why the solution is to enable the following option in Nagios configuration: cgi.cfg :

# File cgi.cfg
# ........
result_limit = 0
# .......

This option tells Nagios to NOT split services in pages, so all services are shown in a single page.