There are two threads in the “Useful User articles” section of the forum on using Splunk.
http://forum.mikrotik.com/t/tool-using-splunk-to-analyse-mikrotik-logs-4-0-graphing-everything/153043/1
And the older one
http://forum.mikrotik.com/t/tool-using-splunk-to-analyse-mikrotik-logs-3-3-graphing-everything/121810/1