Google just released OpenCensus, which is (emphasis mine):

A single distribution of libraries that automatically collects traces and metrics from your app, displays them locally, and sends them to any analysis tool.

The key features of OpenCensus include:

1. Standard wire protocols and consistent APIs for handling trace and metric data.
2. A single set of libraries for many languages, including Java, C++, Go, .Net, Python, PHP, Node.js, Erlang, and Ruby.
3. Included integrations with web and RPC frameworks, making traces and metrics available out of the box.
4. Included exporters for storage and analysis tools. Right now the list includes Zipkin, Prometheus, Jeager, Stackdriver, and SignalFx.
5. Full open source availability for additional integrations and export options.
6. No additional server or daemon is required to support OpenCensus.
7. In process debugging: an optional agent for displaying request and metrics data on instrumented hosts.

This could potentially be a replacement for all the custom tracing frameworks we support in Envoy.

cc @mattklein123 @alyssawilk @htuch