Add support for PgBouncer Exporter
This ships support for my forked version of the Golang pgbouncer_exporter (https://github.com/stanhu/pgbouncer_exporter/), which fixes a number of issues with https://github.com/larseen/pgbouncer_exporter:
- Fixes the metric names to adhere to Prometheus naming standards
- Removes exporting of average and rate metrics, since Prometheus can handle this
- Supports multiple databases with different users (the upstream version would just fail to report any metrics)
- Ignores any non-UTF8 database or usernames. This was happening on the GPRD PgBouncer node.
This is part of gitlab-com/database#27 (closed).