This PoC shows how to 'trick' the Instana Java instrumentation into thinking that a trace and parent span are propagated over an incoming HTTP request, when it case it is not.

The trick is perfomed by injecting the X-INSTANA-T and X-INSTANA-S headers in the request via a Tomcat valve.

The span with the ID specified in the 'fake' X-INSTANA-S header is then sent to Instana via the Trace SDK Web Service.

Edit docker-compose.yaml to configure the agent key for your Instana tenant by editing the value of the INSTANA_AGENT_KEY environment variable accordingly (and, if on-prem or based in a different zone, the INSTANA_AGENT_ENDPOINT environment variable as well).

Then, execute:

./mwnw clean package
docker-compose build
docker-compose up

The application will come up at your Docker's IP (e.g., docker-machine ip) at the URL: http://<docker-ip>:8080/api/google

Spam a few requests, search for the SDK service and MarketXYZ endpoint in Instana, and enjoy :D

Also, the tag rewe.custom_tag will be searchable in the Analyze view via the call.tag filter.