Improve Metrics Exporter

[viral32111]

Improve the Prometheus Metrics Exporter with the new options below.

Remove the metrics command too:

Do not give any commands to act as a daemon, useful for exporting metrics & serving requests from the JSON API.

Proposed CLI flags including types, defaults & usage:

• [--metrics-address <string (def. '127.0.0.1')>] - The IP address to listen on for the HTTP Prometheus metrics exporter.
• [--metrics-port <number (def. 5000)>] - The port number to listen on for the HTTP Prometheus metrics exporter.
  • Can serve on the same port as the JSON API (--api-port).
  • Set to 0 to disable the metrics exporter.
• [--metrics-path <string (def. '/metrics')>] - The HTTP path to the metrics page.
  • If serving on the same port as the JSON API, ensure this is not the same as an API route.
• [-u/--metrics-authentication <string>] - Colon separated username & password for HTTP basic authentication.
  • Authentication is disabled if this is not given, allowing unrestricted access.
• [-i/--metrics-interval <number (def. 15)>] - The time in seconds to wait between collecting metrics.
• [--disable-metrics-logging] - Disables logging of metrics collection and HTTP requests/responses to the console.
• [--metrics-log-file <string (def. 'metrics.log')>] - The path to a file to log metrics collection and HTTP requests/responses to.
  • Leave blank or set to /dev/null to disable logging to file.