
Install mysqld-exporter with snap. It's a prometheus exporter for mysql, which provide the http interface for prometheus to pull the metrics. It should only install & setup configuration when relation connect to prometheus, and disable when relation remove. The charm also need to create read only user for the exporter to get the metrics. https://github.com/prometheus/mysqld_exporter Change-Id: Id6a6337004586699c7f943530fa7a32deae26db0 func-test-pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/859