CommonVolumeRadarWorker was enqueuing one job per contact — every
job fetched + decoded the ~5 MB n0q PNG for its own 5-min frame.
At current backlog depth that's 17,588 contacts across just 1,747
distinct 5-min frames, i.e. ~10 contacts per frame paying for the
same PNG decode over and over.
New RadarFrameWorker takes a batch of contact_ids sharing one frame,
fetches + decodes the frame ONCE, then walks the in-memory pixel
buffer per contact. build_radar_jobs/1 in ContactWeatherEnqueueWorker
now groups the input contacts by their rounded 5-min timestamp and
emits one RadarFrameWorker job per frame instead of one
CommonVolumeRadarWorker per contact.
process_frame/4 is public so the same code path is used both by
perform/1 (production fetch) and tests (pre-decoded pixel buffer);
keeps the happy-path test hermetic without hand-crafting a PNG.
CommonVolumeRadarWorker stays in the tree — still used from the
single-contact submit path where batching is pointless and the
aggregate_stats/5 pure helper is a dependency of the new batched
worker.
Expected impact on the backfill: ~10x fewer fetch + decode cycles,
so the 17k queued-contact backlog drains in minutes instead of ~50.
Graham McIntire
b6b5945002