It seems the automagic config for the graphite server in MwddSettings.php#L247 isn't working and needs to be just 'graphite' instead of 'graphite-statsd'.

This should be as simple a fix as updating the host in the file.
You should then be able to verify that metrics make their way from MediaWiki into graphite when the service is running.

Contribution guide...

The code repository is on the Wikimedia gitlab instance https://gitlab.wikimedia.org/repos/releng/cli and is written in GO
Documentation for mwcli is at https://www.mediawiki.org/wiki/Cli (This includes an installation guide, and first setup guide for the dev environment).
If you want to pick up this task please ask @Addshore to be added to the project first. This way you will be able to create a branch on the repository and have CI run.