StatsD is a front-end proxy for the Graphite/Carbon metrics server, originally written by Etsy’s Erik Kastner. It’s ideas come from Flickr and this post by Cal Henderson: Counting and Timing. The server was written in Node, though there have been implementations in other languages since then.
CollectD gathers statistics about the system it is running on and stores this information. Those statistics can then be used to find current performance bottlenecks (i.e. performance analysis) and predict future system load (i.e. capacity planning). The fundamental difference between collectd and other aggregators of like manner is that collectd is written in C for performance and portability, allowing it to run on systems without scripting language or cron daemon, such as embedded systems.
The Beats platform provides lightweight data shippers for various types of data for enrichment via Logstash into Elasticsearch.