The Synapse database grew from 2.2 GB (after the July cleanup) to
6.2 GB, almost all of it state_groups_state from large federated rooms
with one or two local members.
synapse_auto_compressor (matrix-org/rust-synapse-compress-state, built
from main) now runs nightly at 04:30, after the 03:00 vzdump backup.
It verifies compressed state against the original, writes each state
group in its own transaction, skips chunks that would not shrink, and
resumes from stored progress. The initial backlog took ~8 minutes with
no Synapse errors: state_groups_state 11.0 M -> 4.25 M rows (-61%).
Also documents the new "Synapse Database Growing Fast" Grafana alert
(> 500 MB in 7 days).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5
