I have installed Nagios 3.0.3 two different ways (compiled it myself and MacPorts) and am having similar problems with the amount of CPU time being consumed by the application. In each case once I start Nagios in Daemon mode (-d) it consumes 100% CPU and seldom goes below 98%. After 20 minutes of running it is now running at 201% CPU. It looks like it will consume all available CPU in about an hour's time.
I have Apple XServer (Intel Dual CPU/Dual Core) so I have up to 400% CPU capacity, but Nagios is using way too much CPU. I have an installation of Nagios 2.x running on SuSE Linux 10.0 and it runs fine. I am using almost the same configuration files on the two systems (with adjustments for the different directory locations) and for some reason the Apple installation is eating up the processors.
Has anyone else seen similar problem?
I didn't try to compile the source using 64 bit arch, but may do that to see if it makes any difference. The MacPorts installation is doing the same thing as the native build and may be on an even faster CPU consumption growth path. I also may try to compile the 2.x version and see if it gives the same result.