Batch Convert Images to SVG

When you have many images to convert — a 20-icon set, or product thumbnails to ship as SVG — Batch Convert fans N jobs out into the BullMQ queue. Each file is processed in parallel (concurrency 2), with real-time per-file progress tracking.

Once everything is done, the server packages the results with archiver into a single ZIP for download. Source images are deleted as soon as each worker finishes; the ZIP lives for 1 hour. Dozens of uploads and downloads collapsed into one.

When you upload 20 files, /api/batch creates 20 independent jobs on the BullMQ 'SVGProcessing' queue, all sharing one batchId (UUID v4). Every job has its own jobId (BullMQ auto-generated numeric ID) and lands in Redis with data: {batchId, batchIndex, type, inputPath, outputPath, options}.

The worker pool runs concurrency=2 (our server is a dual-core i5), so two files trace in parallel at any time. When a worker finishes a job it picks up the next one from the queue. Per-job progress flows through Redis pub/sub to the client; the front-end polls /api/batch/[batchId] every 1.5s to update the UI.

Once every job in a batch hits 'completed' or 'failed', POST /api/batch/[batchId]/zip streams chunks via archiver (Node stream-based ZIP) — never loading all files into memory, so large batches don't OOM. The ZIP contains every successful SVG with its original filename. A cleanup cron runs every 30 minutes and deletes ZIPs older than 1 hour.