OpenCensus: A Stats Collection and Distributed Tracing Framework

TL;DR: Google created an open source version of the internal Census library. We use Census to monitor/debug systems at scale.

It's a single distribution of vendor-neutral libraries that automatically collects traces and metrics from your app, displays them locally, and sends them to any analysis tool (we currently have exporters for Zipkin, Prometheus, Datadog, Stackdriver, and Azure App Insights).