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This is an example of distributed tracing across 3 applications:

• Client
• Service A (running on port 12345)
• Service B (running on port 12346)

Client --RPC--> Service A --RPC--> Service B

The client makes an RPC request to service A, which in turn makes an RPC request to service B, then responds to the client.

The tracing implementation used in this example is Jaeger. Mu-Scala integrates with Natchez to abstract over this, so the only mention of Jaeger is in the entrypoint of each application.

First start a Jaeger server in a Docker container:

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

Next start Service B:

sbt serverB/run

Then in another terminal window, start Service A:

sbt serverA/run

Finally start the client application:

sbt client/run

Enter your name when prompted. The client will send a request (actually a few identical requests) to Service A.

Open the Jaeger UI (http://localhost:16686/search) and search for traces for the my-client-application service. Open the most recent trace. You should see a trace that spans across all 3 services.