wgrib2 -lola ... bin writes Fortran unformatted records (4-byte
length header + data + 4-byte length trailer per message).
parse_lola_binary was treating the binary as tightly packed,
causing every message after the first to read from the wrong
offset — values came out as garbage across all grid points.
Fix: account for the 8-byte record overhead per message when
computing the data offset for each message's grid values.
This bug affects both the existing propagation grid extraction
(which may have been producing subtly wrong scores) and the new
native-level extraction (which was producing obviously wrong
values). The fix is a one-line stride change.
Also adds Backtest.Features.native_surface_refractivity for the
Phase 1 sanity check, plus a tighter wgrib2 match pattern that
selects only hybrid-level messages from the native file.
Per-point ERA5 fetches were tragically slow because every point-hour
triggered its own asynchronous CDS job (submit → poll → assemble →
download). For backfill this meant thousands of independent jobs
queued against Copernicus. The new path groups requests by calendar
month and a 2° × 2° lat/lon tile so one CDS cycle populates ~60k
profiles at once, and Oban uniqueness on (year, month, tile_lat,
tile_lon) collapses every duplicate enqueue.
- Era5BatchClient builds the monthly CDS requests, extracts every
(lat, lon, hour) from the GRIB2 blob with wgrib2, derives
refractivity params, and bulk-inserts in 2k-row chunks with
on_conflict: :nothing. fetch_month_into_db/1 short-circuits when
the month-tile already has any cached profile.
- Era5MonthBatchWorker runs the batch on the :era5 queue with a
generous backoff (10m → 1d) and the uniqueness key above.
- Era5FetchWorker is now a thin router: cache hit → :ok, cache miss
→ enqueue the month-batch for the point's tile-month and return.
No more per-point CDS calls.
- Wgrib2 grows extract_grid_messages/3 which preserves per-message
datetimes by parsing `d=YYYYMMDDHH[MMSS]` from the inventory, so a
single GRIB2 file carrying a whole month decodes correctly.
- The era5_backfill mix task enqueues month-tile batches directly.
Add a separate wgrib2-builder stage that compiles wgrib2 from source.
Docker layer caching means this only builds once — subsequent deploys
reuse the cached layer. The binary is copied into the final runtime
image. Also fixed wgrib2 path lookup to be runtime instead of
compile-time so it works in the Docker build pipeline.
Add Wgrib2 module that shells out to wgrib2 binary for fast GRIB2
grid extraction using -lola (nearest-neighbor to regular lat-lon grid).
Falls back to pure-Elixir decoder if wgrib2 is not installed.
Also: parallel GRIB2 range downloads, merge adjacent byte ranges,
skip corrupt messages instead of failing, pressure fetch is optional.
