monitor_ssl_key
The private key used for the Server Health and Metrics HTTPS listen. If it is included in the digital certificate in monitor_ssl_identity, then this parameter is not needed.
monitor_ssl_key = private_key
If none of monitor_ssl_identity, monitor_ssl_key, monitor_ssl_trusted, and monitor_ssl_password are set, the private key file configured for the server’s TLS listen (ssl_server_key) is used in its place. If that private key file is also not specified, the server will fail to start up.
This parameter supports private keys in the following formats: PEM, DER, PKCS#8, PKCS#12.
You must specify a path to a file that contains the key.