Distributed Tracing
Since the adoption of SOA/microservice architectures (with REST services taking a central place in them), systems become more and more distributed. The importance of having the visibility of how each request travels from the client to the service and from service to service till the eventual response is being constructed is hard to overestimate. Distributed tracing systems are designed to solve that. The most widely used and known ones are Twitter Zipkin and Apache HTrace (currently in incubation), both built on top of Google's paper Dapper, a Large-Scale Distributed Systems Tracing Infrastructure