Zipkin – Distributed Tracing
Another Open Source project from Twitter. Functionality and the screen shot on the home page make interesting reading.
Zipkin is a distributed tracing system that helps us gather timing data for all the disparate services at Twitter. It manages both the collection and lookup of this data through a Collector and a Query service
Not surprise to see Cassandra usage in the architecture
Anyone used Zipkin from a Capital Markets perspective?
Tales from a Trading Desk 
Would be interesting to see how Zipkin compares with commercial products such as Optier. From the description it would appear to have a significantly more sophisticated query capability.