Grafana Dashboard - add WAL count

[pchovelon]

It could be great to have the number of WAL in the pg_wal folder, regardless their state.

[gbartolini]

@pchovelon have you considered also some of the metrics below (taken from here? Is there any other which can be relevant?

cnpg_collector_pg_wal{value="count"} 9
cnpg_collector_pg_wal{value="slots_max"} NaN
cnpg_collector_pg_wal{value="keep"} 32
cnpg_collector_pg_wal{value="max"} 64
cnpg_collector_pg_wal{value="min"} 5
cnpg_collector_pg_wal{value="size"} 1.50994944e+08
cnpg_collector_pg_wal{value="volume_max"} 128
cnpg_collector_pg_wal{value="volume_size"} 2.147483648e+09

For example, if WALs are in a separate volume, count/volume_max indicates the current usage of the WAL volume.

[pchovelon]

No I didn't, as I think only the "count" is missing.
For the usage of the WAL volume I thought the panel "Volume Space Usage: PGDATA and WAL" already gives us this information.

[itay-grudev]

The panel was added to the dashboard in https://github.com/cloudnative-pg/grafana-dashboards. When #225 is merged, the updated version will also apply to the helm chart, so I'm closing this.