XFS quota support?

[jkroepke]

Hi,

node_exporter already supports exposing multiple XFS related metrics. Would it be possible to add support for xfs quotas or is it out of scope of this project?

[jkroepke]

I looked deeper into the available Linux interfaces. There seem to be two possible implementations, and I would like to know which approach would be preferred before preparing an upstream PR.

Option 1: Q_XGETNEXTQUOTA

Use the quotactl syscall directly from Go to enumerate all XFS project quota records.

This provides:

• used bytes and inodes
• separate soft and hard limits
• project IDs without requiring /etc/projects
• optional project ID-to-path information from /etc/projects

The collector could be disabled by default, with device and project_id labels. However, Linux requires CAP_SYS_ADMIN for Q_XGETNEXTQUOTA.

The add a project_id filesystem mapping, read /etc/projects is nessesary as well.

Option 2: statfs

Read /etc/projects and call statfs for every configured project path.

This works without additional capabilities because XFS adjusts the statfs result according to the directory’s project quota.

The limitations are:

• /etc/projects or another path configuration becomes mandatory
• projects cannot be enumerated
• only projects with known paths can be collected
• XFS reports the soft limit when configured, otherwise the hard limit
• separate soft and hard limit metrics are therefore not possible

Neither implementation would execute the xfs_quota CLI.