rocks_spool_estimate_pending_compaction_bytes
Estimated total bytes that compaction needs to rewrite to bring all levels back under their target sizes.Info
This metric has labels which means that the system will track the metric for each combination of the possible labels that are active. Certain labels, especially those that correlate with source or destination addresses or domains, can have high cardinality. High cardinality metrics may require some care and attention when provisioning a downstream metrics server.
Since: Version 2026.09.22-a276d4a8
The functionality described in this section requires version 2026.09.22-a276d4a8 of KumoMTA, or a more recent version.
This is a backlog indicator. Steady-state values depend heavily
on write rate, compression, and the configured compaction style,
so absolute thresholds should be derived from each deployment's
baseline. Unbounded growth over a multi-hour window indicates
that compaction cannot keep up with the write rate, which
eventually leads to write slowdown
(rocks_spool_actual_delayed_write_rate becomes non-zero) and
then to write stop (rocks_spool_write_stopped becomes 1).
Only meaningful for level-style compaction.