Natchez Trace

This is an minimal distributed tracing effect for Cats, inspired by earlier work done on puretracing. It currently has integration with:

It supports

spans
numeric, string, and boolean fields
swizzling to and from http headers

It does not support

logs
baggage

If you can make a case for either of these ideas I will consider supporting them, but they seem unnecessary to me.

The Trace effect looks like this:

def doStuff[F[_]: Trace]: F[Whatevs] =
  Trace[F].span("span here") {
    // Do stuff in F here. This is the extent of the span.
    // You can use the instance to:
    //  - create child spans
    //  - set data fields
    //  - extract a set of headers to pass to a remote
    //    service, which can then continue the trace
  }

To try it out start up Jaeger as your trace collector.

docker run -d --name jaeger \
  -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 \
  -p 5775:5775/udp \
  -p 6831:6831/udp \
  -p 6832:6832/udp \
  -p 5778:5778 \
  -p 16686:16686 \
  -p 14268:14268 \
  -p 9411:9411 \
  jaegertracing/all-in-one:1.8

Now, finally, if you run the example in modules/examples and go to localhost:16686 you can then select natchez-example and search for traces.

To use it in your own projects (not recommended yet) you can do

// search at sonatype or central for latest version, sorry
libraryDependencies += "org.tpolecat"  %% "natchez-jaeger" % <version>