The flat-mount overlay's caddy `volumes: !override` block listed only
three mounts, but the base docker-compose.yml caddy service has five.
`!override` (compose-spec semantics) replaces the entire list, so two
mounts were silently dropped under the flat layout:
- `data:/srv:ro` — Caddy's read-only view of the agnes data dir, used
by the `@download` file_server handler in Caddyfile (added in v0.36.0
as the perf bypass for multi-GB parquet downloads). Without this
mount, `try_files /bigquery/data/<id>.parquet …` finds no file and
every parquet download falls through to the app's uvicorn worker —
defeating the bypass entirely.
- `caddy_config:/config` — Caddy's autosave/ACME state. Less critical
(we feed certs in via /certs) but loses the autosaved adapter config
across container recreates.
Restated both mounts with a comment block explaining the !override
caveat for any future overlay author.
Plus: CHANGELOG entries for the host-mount.yml direct-bind fix and
the STATE_DIR + flat-mount overlay under [Unreleased].
Introduces STATE_DIR as the single source of truth for the writable
state directory path, with backward-compatible default of
${DATA_DIR}/state. Pairs with a new docker-compose.flat-mount.yml
overlay that mounts the state disk in PARALLEL to the data disk
(rather than nested under it).
Why
---
The default deployment topology nests state under data: sdb at /data,
sdc at /data/state. That layout has known fragility documented in
docs/state-dir.md — bind-propagation gotchas, two-writer collisions
on the same prefix, mount-order coupling. The 2026-05-05 incident in
the Groupon FoundryAI deployment was a manifestation of the
propagation gotcha.
The flat layout (sdb at /data, sdc at /data-state — parallel, not
nested) eliminates the nested-mount class entirely. Each disk is its
own bind mount, recursive by default in modern Docker. No volume
options to forget. No two-writer collision (host scripts and
container app share /data-state at the same path, single namespace).
What changes
------------
App code (Python):
- src/db.py: new _get_state_dir() helper. get_system_db() and
schema migration snapshot use it.
- app/secrets.py: new _state_dir() helper. _load_or_generate() uses
it for .session_secret and .jwt_secret.
- app/main.py: .env_overlay loaded from _state_dir().
Host scripts:
- scripts/ops/agnes-auto-upgrade.sh: STATE_DIR drives mount-sanity
check and cert detection. Defaults preserve existing behavior.
- scripts/ops/agnes-tls-rotate.sh: STATE_DIR drives CERT_DIR.
New compose overlay:
- docker-compose.flat-mount.yml: parallel /data and /data-state binds
per service. Mutually exclusive with docker-compose.host-mount.yml;
pick one based on disk topology.
Documentation:
- docs/state-dir.md: layout choice (A nested vs B flat), pros/cons,
migration steps, and which code paths read STATE_DIR.
Backward compatibility
----------------------
STATE_DIR defaults to ${DATA_DIR}/state — current behavior. Existing
deployers that don't set the var see no behavior change. Migration
to flat layout is opt-in per the runbook in docs/state-dir.md.
Validation
----------
- bash -n on both host scripts: pass
- docker compose config -f docker-compose.flat-mount.yml: resolves
cleanly with all 6 services binding /data and /data-state directly
- python3 import + helper exercise: STATE_DIR override works,
default falls back to ${DATA_DIR}/state
Companion to PR #191 (drop named-volume driver_opts in host-mount.yml).
That PR fixes the immutability footgun for Layout A; this PR offers
Layout B as the architectural alternative.
