Teamcity can be integrated with Grafana in order to gather statistics about builds and agents activity. In order to gather those teamcity metrics you will need a prometheus installation and then a configuration for the teamcity source.
When you connect teamcity as a target on prometheus you have two options regarding an https secure communication. Either you trust the not verified certificate and place that in the configuration file, or you should enable tls communication with certificates between teamcity and prometheus.
If you do not set one of the two options on prometheus you might end up with the issue:
Get /app/metrics remote error: tls handshake failure
The first option as discussed would be to trust the insecure certificate using https.
tls_config: insecure_skip_verify: true
The second option would be to communicate through certificates. First create a new folder inside your Prometheus installation and store the certificates for the teamcity server. Then you will need to point the files in the configuration.
tls_config: ca_file: /var/prometheus/ssl/signalocean.com.crt
The detailed options for tls_config in prometheus can be found below.