Reaper exposes all its metrics in a Prometheus-ready format under the /prometheusMetrics endpoint on the admin port.
It’s fairly straightforward to configure Prometheus to grab them. The config can look something like:
scrape_configs:
- job_name: 'reaper'
metrics_path: '/prometheusMetrics'
scrape_interval: 5s
static_configs:
- targets: ['host.docker.internal:8081']
host.docker.internal tells a Prometheus instance running inside a docker container to connect to the host’s 8081 port where Raper runs from a JAR.