I'm using Google Cloud's Stackdriver Trace Agent with the Express.js plugin.
I noticed there are a few routes which have substantial "untraced" time. What strategies can I use to find and begin to measure these untraced paths, and why would it not pick up certain code paths?
If the Trace agent isn't working, there's unfortunately not very much you can do to modify its behavior. I recommend using OpenCensus to instrument your application, which will give you much more control over exactly how traces and spans are created.