EpMon is a standalone python based process and is for every OpenStack service it find in the service catalogs send GET requests to the configured endpoints.
Performing extensive tests like provisioning a server is giving a great coverage, but is usually not something what can be performed very often and leaves certain gaps on the timescale of monitoring. In order to cover this gap EpMon component is capable to send GET requests to the given URLs relying on the API discovery of the OpenStack cloud (perform GET request to /servers or the compute endpoint). Such requests are cheap and can be performed in the loop i.e. every 5 seconds. Latency of those calls, as well as the return codes are being captured and sent to the metrics storage.