The A1 Policy Management Service Spring Boot application exposes some management endpoints including loggers, metrics, Prometheus, and so on...
All these endpoints are enabled by Spring Boot Actuator dependency. When this dependency is added in pom.xml, it will expose counters and statistics, which can then be managed from application.yaml. 
(See Kohn London - Component configuration) for more details on configuration, and the application.yaml file)

...

• http://localhost:8081/actuator/health or http://localhost:8081/actuator/prometheus

Prometheus Statistics

Prometheus is time-series database, which stores a sequence of data points, across time. It’s generally used to store metrics and performance data from your applications.

There are numerous predefined Prometheus statistics and counters, however we have added 3 new A1-specific metrics for the the A1 Policy Management Service:

• total_ric_count
  • Type Guage Gauge: The count of configured rics avaialbleavailable/used by the A1 Policy Management Service
• total_policy_type_count
  • Type Guage Gauge: The total count of available A1 Policy types
• total_policy_count
  • Type Guage Gauge: The total count of available A1 Policy instances

An example of Prometheus statistics:

Prometheus UI

If you want to collect and visualize Prometheus' statistics in Prometheus GUI, this can be configured in a  'prometheus.yml' Prometheus configuration file, similar to the example below.
This sample shows how Prometheus can periodically scrape the available metrics and make them available.

...