A prometheus couchbase exporter!

All others I found seem to be abandoned and/or very incomplete. This is an attempt to have all metrics exported, including task-related metrics!

Innitially, have the same metrics as our old exporter, to facilitate the migration.

Once that's done, we can better document all metrics, eventually improve their naming (like adding _total, _seconds, _byte prefixes), and finally, provide example alerting rules and grafana dashboards, so it's easier to proper monitor a couchbase cluster.

It's worth saying that we will only support Couchbase 5 for now.

$ couchbase-exporter --couchbase.username adm --couchbase.password secret

check couchbase-exporter --help for more options!

• the exporter itself
• a grafana dashboard
• an example of alerting rules

• export task metrics
• export bucket metrics
• export node metrics
• export cluster metrics
• provide alerting rules examples
• provide grafana dashboards (maybe use jsonnet (https://github.com/grafana/grafonnet-lib)?)
• check other TODOs
• improve metric names (add _bytes, _seconds, _total, etc)
• add some sort of tests