By default tracing is disabled. To enable it there are two ways:

A) System Property

Change the flag otel.sdk.disabled to false in the application.yaml (New Delhi) 

otel:
  sdk:     
    disabled: ${ONAP_SDK_DISABLED:false}
    south: ${ONAP_TRACING_SOUTHBOUND:true}   
  instrumentation:
    spring-webflux:
      enabled: true

1. otel.sdk.disabled: enable/disable tracing all together
2. otel.sdk.south: if ONAP_SDK_DISABLED is false then we can enable/disable southbound tracing
3. otel.instrumentation.spring-webflux.enabled: if ONAP_SDK_DISABLED is false we can enable/disable northbound tracing

B) Enviroment Variable

Have the environment variables, this way you don't need to change the application.yaml and rebuild the docker image

ONAP_SDK_DISABLED=false
ONAP_TRACING_SOUTHBOUND=true
OTEL_INSTRUMENTATION_SPRING_WEBFLUX_ENABLED=true

1. ONAP_SDK_DISABLED: enable/disable tracing all toghether
2. ONAP_TRACING_SOUTHBOUND: if ONAP_SDK_DISABLED is false then we can enable/disable southbound tracing
3. OTEL_INSTRUMENTATION_SPRING_WEBFLUX_ENABLED: if ONAP_SDK_DISABLED is false we can enable/disable northbound tracing

Possible Combinations 

So we can have the following combinations:

Tracing	Northbound	Southbound	Flags
			ONAP_SDK_DISABLED=true
			ONAP_SDK_DISABLED=false; ONAP_TRACING_SOUTHBOUND=true; OTEL_INSTRUMENTATION_SPRING_WEBFLUX_ENABLED=true
			ONAP_SDK_DISABLED=false; ONAP_TRACING_SOUTHBOUND=false; OTEL_INSTRUMENTATION_SPRING_WEBFLUX_ENABLED=true
			ONAP_SDK_DISABLED=false; ONAP_TRACING_SOUTHBOUND=true; OTEL_INSTRUMENTATION_SPRING_WEBFLUX_ENABLED=false

Example

In a docker compose scenario:

services:
  a1_policy_management:

        ....
    environment:
      - ONAP_SDK_DISABLED=false
      - ONAP_TRACING_SOUTHBOUND=true
      - OTEL_INSTRUMENTATION_SPRING_WEBFLUX_ENABLED=true

For more information visit the wiki page