require-in-the-middle VS zipkin-js

Of course, in the real thing, there's a lot more, like caching, resolving module paths, and handling race conditions. If you'd like to read more about the module system, the Node.js docs are pretty detailed. I've also written a bit about some testing libraries that hook into the Node.js module system. And here's an example of someone else hooking into require.

The manual approach is alright for recording custom operations, but it can get pretty tiring doing it for every database query or API call. For that, there's another approach: having the dev explicitly request instrumented wrappers of their libraries. For instance, to automatically [instrument your PostgreSQL queries with Zipkin, you'd need to wrap the pg module with Zipkin's library and use that for your database queries.