Cricket is a high performance, flexible system for monitoring trends in time-series data. It was developed to help network managers visualize and understand the traffic on their networks, but it can be used for all kinds of other jobs, as well. It features a hierarchical configuration system (which avoids duplicate info in the config files), full flexibility in RRD structure (arbitrary numbers of DS's and RRA's), a CGI-based graph-on-demand application, and SNMP- and EXEC-based data gathering.
