I'm looking for a free solution that allows operators to keep an eye on systems and applications. It should digest log files from different sources and allow for alerts to be triggered in certain conditions.
I guess this is a trivial question for most of you, but I am less familiar with these types of applications.
Thank you! J.
Ask anyone in the game about monitoring, and they're bound to mention Nagios. On of the great things about Nagios is that it is simply a scheduling and reporting engine. Its trivial to write plugions to monitor the things you want to measure - and lots of people have done that or to put new front ends on. Zabbix provide a nicely packaged verion.
There are probably plugins for log analysis (a quick goole turned up this) but writing your own is easy. Alternatively (or in addition) you might want to have a look at Splunk which is specifically a tool for manipulating log files.
Or, as an alternative, you could look at Icinga, which is a fork of Nagios.
Tivoli Enterprise Console is also a "rules engine" which Nagios is not. Freely available, open source alternatives to that are ZenOSS and OpenNMS (you would have to add it yourself).