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Grab fails: Transmission cannot fetch Prowlarr download URLs #100

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opened 2026-08-23 07:50:33 +01:00 by naps62-yolo · 1 comment
naps62-yolo commented 2026-08-23 07:50:33 +01:00
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Found on the first real cutover test. Both movie grabs fail with Transmission RPC failed: Couldn't fetch torrent: No Response (0).

The grab pipeline passes the Prowlarr download_url straight to Transmission's torrent-add filename. Two problems compound:

  1. prowlarr.n62.casa is behind the Traefik VPN/docker ACL; the Transmission LXC (10.6.10.45) is not in it, so its fetch gets no response.
  2. Prowlarr's download endpoint often 301-redirects to a magnet: URI anyway (verified live), which a URL fetch cannot follow into a file.

Fix in arr-dl/grab, not infra: arr resolves the download itself — it can reach Prowlarr and already holds the API key. GET the download URL without following redirects; on a redirect to magnet:, pass the magnet as filename; on a 200 with a torrent body, pass base64 metainfo. Transmission then needs no Prowlarr access at all. Keep the blacklist/hash checks intact.

Depends on: (nothing open)

Labels: phase/4-movies, area/dl, difficulty/moderate, type/bug

Found on the first real cutover test. Both movie grabs fail with `Transmission RPC failed: Couldn't fetch torrent: No Response (0)`. The grab pipeline passes the Prowlarr `download_url` straight to Transmission's `torrent-add filename`. Two problems compound: 1. `prowlarr.n62.casa` is behind the Traefik VPN/docker ACL; the Transmission LXC (10.6.10.45) is not in it, so its fetch gets no response. 2. Prowlarr's download endpoint often 301-redirects to a `magnet:` URI anyway (verified live), which a URL fetch cannot follow into a file. Fix in `arr-dl`/grab, not infra: arr resolves the download itself — it can reach Prowlarr and already holds the API key. GET the download URL without following redirects; on a redirect to `magnet:`, pass the magnet as `filename`; on a 200 with a torrent body, pass base64 `metainfo`. Transmission then needs no Prowlarr access at all. Keep the blacklist/hash checks intact. Depends on: (nothing open) Labels: `phase/4-movies`, `area/dl`, `difficulty/moderate`, `type/bug`
naps62-yolo added the area/dldifficulty/moderatephase/4-moviestype/bug labels 2026-08-23 07:50:53 +01:00
naps62-yolo commented 2026-08-23 08:00:20 +01:00
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Fixed on main in 4afe44c.

arr now resolves the indexer download link itself: it GETs the Prowlarr link without following redirects, sends the magnet as filename when the link redirects to one, and sends the torrent bytes as base64 metainfo when it returns a body. Transmission needs no Prowlarr access. The blacklist name and infohash checks are unchanged.

Also removed TorrentSource::Url, which was the shape that encoded the bug.

Fixed on main in 4afe44c. arr now resolves the indexer download link itself: it GETs the Prowlarr link without following redirects, sends the magnet as `filename` when the link redirects to one, and sends the torrent bytes as base64 `metainfo` when it returns a body. Transmission needs no Prowlarr access. The blacklist name and infohash checks are unchanged. Also removed `TorrentSource::Url`, which was the shape that encoded the bug.
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area/api
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 area/ci
CI and test harness
 area/compat
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 area/core
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 area/daemon
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bounded, obvious approach, few files
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one file, mechanical, no design decisions
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parsing and policy engine, pure, no network
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movies end to end
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Reference: yolo/arr#100