The /skewt page was empty in prod because Phase 2 of the Rust cutover
moved f01..f18 grid scoring to Rust but left profile-file writing only
on the analysis (f00) path. Result: /data/scores/profiles/ accumulated
one file per chain run instead of nineteen, so SkewtLive only ever saw
the analysis hour — and that hour falls outside the 1 h past cutoff
within an hour of the chain finishing, leaving the page empty most of
the time.
Two surgical fixes:
* `pipeline::run_chain_step` now builds `profile_entries` alongside
`prepared` from the merged grid in a single iter pass, then spawns
`profiles_file::write_atomic` on the blocking pool to overlap the
NFS write with the score-band scoring/write fan-out — same pattern
`run_analysis_step` already uses. `ChainStepStats` gains
`profile_cells_written` so the worker log line is symmetric with
the analysis step's existing field and a future failure mode that
drops the profile would show up as a divergence.
* `SkewtLive.available_valid_times/0` widens the past cutoff from
1 h to 3 h. The chain's analysis hour can be ~70 min old by the
time the next chain finishes (and ~2 h on a missed cycle), so the
1 h cutoff was leaving the page blank during normal transients.
18 h forward window unchanged.
Cosmetic: cargo fmt picked up trivial rewrites in decoder/fetcher/
native_duct/hrrr_point_worker that had drifted; rolled in.
Verification: cargo build --release, cargo clippy --lib --bins -D
warnings, cargo test --lib (134/134), mix test
test/microwaveprop_web/live/skewt_live_test.exs (3/3) all green.
The decoder's `parse_lola_binary` inserts the same "VAR:LEVEL"
string into ~92k cell maps for every one of ~60 GRIB2 messages in
a chain step — previously a String::clone per cell, yielding
~5.5M heap allocations and frees per hourly run. Switching
`CellValues` from `HashMap<String, f32>` to
`HashMap<Arc<str>, f32>` makes each insertion a single atomic
refcount increment: the string is allocated once per message, and
`Arc::clone` is cheap from there.
Callers were mostly unchanged — `cell.get("...")` still works via
`Arc<str>: Borrow<str>`. Two touch-ups needed: native_duct.rs had
a couple of `cell.get(&format!(...))` lookups that were passing
`&String` (triggering the wrong Borrow impl) — switched to
.as_str(), and the test fixtures' `.insert(format!(...), _)` now
need a `.into()` to coerce into `Arc<str>`. Zero behavior change.
Extracts the memory-hostile HRRR fetch → decode → score pipeline for
forecast hours 1–18 into a separate Rust service (`prop-grid-rs`).
Elixir retains f00 with its native-duct + NEXRAD + commercial-link
enrichment; Rust handles the other 18 steps per hourly chain.
Hand-off via a new `grid_tasks` table (`FOR UPDATE SKIP LOCKED` claim
from Rust, Postgrex `NOTIFY propagation_ready` back to Elixir). Rust
writes the same on-disk score-grid format Elixir already uses, to the
same `/data/scores` NFS tree. Phase 1 ships in shadow mode with
PROP_SCORES_DIR=/data/scores_shadow.
Rust crate layout at `rust/prop_grid_rs/` (1:1 module parity with the
Elixir source it ports):
- grid, region, band_config, scores_file, sounding_params
- scorer: all 10 factors + composite. Matches the Elixir scorer
byte-for-byte across 115 golden-fixture samples (5 scenarios
× 23 bands).
- decoder: wgrib2 subprocess + Fortran-record lola-binary parser
- fetcher: HRRR URL derivation + idx cache (1h TTL) + 8-way
parallel byte-range downloads with 429/5xx retry
- pipeline: end-to-end chain step, f00 rejected at the boundary
- db: sqlx grid_tasks claim/complete + propagation_ready NOTIFY
- bin/worker: tokio main loop, JSON logs, SIGTERM-safe
91 Rust tests + clippy -D warnings clean. 2,158 Elixir tests green.
Elixir additions:
- `GridTaskEnqueuer` seeds fh=1..18 rows from
`PropagationGridWorker.seed_chain/0`
- `NotifyListener` LISTEN → warm `ScoreCache` → PubSub fan-out
- `ShadowComparator` diffs prod vs shadow `.ntms` bodies
- `mix rust.golden` task writes the Rust-side golden fixture
k8s: new `deployment-grid-rs.yaml` pinned to talos5 (32 GB NUC) via
`prop-grid-rs=primary` nodeSelector + `workload=grid-rs:NoSchedule`
toleration, 512 Mi limit, sharing the existing NFS `/data` mount.
The plan document is at `plans/vivid-hatching-quail.md` (local to my
workstation); phases 2 (cutover) and 3 (talos5 concurrency tuning)
follow after 72h of shadow-mode parity.
