83298dabf3
- Omit/invalid/<=0 LIDARR_MEDIA_IO_PARALLELISM: default ParallelOptions for folder scan + tag reads (matches original multithread fork). - PLINQ candidate scoring: ProcessorCount when uncapped; same 1–64 cap when set. - Fixes throughput loss from equating 16 cores with TPL default concurrency. - Log line shows TPL default vs cap and PLINQ degree; update MULTITHREAD_README. Made-with: Cursor
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Multithreaded library scan / import (this fork)
This branch adds a faster, parallel disk scan and import path. Upstream Lidarr does much of this work sequentially; this fork parallelizes folder scanning, tag reads, and release-candidate scoring.
A Dockerfile.multithread in this repository builds a self-contained binary and overlays it on ghcr.io/linuxserver/lidarr:nightly (see CI or build from repo root per that file’s comments). A wrapper layout that keeps this tree in a lidarr-src/ subdirectory can use the parent Dockerfile instead.
LIDARR_MEDIA_IO_PARALLELISM (optional IO cap)
Parallel import work is not limited by Lidarr’s download bandwidth or rate settings (those apply to indexers/clients only). On slow or remote storage (especially NFS), the default uncapped parallelism can saturate IOPS. Set this variable only when you need to limit concurrency.
| Name | LIDARR_MEDIA_IO_PARALLELISM |
| Omit / empty / invalid / ≤0 | Original fork behavior: Parallel.ForEach uses the TPL default (MaxDegreeOfParallelism = -1), which can use more concurrent workers than ProcessorCount on I/O-heavy work (this is why setting 16 on a 16-core box could feel slower than before). PLINQ still uses ProcessorCount (TagLib / candidate scoring cannot use -1). |
| 1–64 | Hard cap on both Parallel.ForEach loops and PLINQ degree (same number). Use 1–2 on NFS if the host stalls. |
| Scope | Environment is read when each parallel section runs |
Docker: set on the container like any other env variable.
On the first disk scan, Lidarr logs Media import parallelism: with TPL default (-1, uncapped) or your numeric cap, plus PLINQ degree and host ProcessorCount.
Docker Compose
services:
lidarr:
image: your-registry/lidarr-nightly-multithread:latest
environment:
- PUID=1000
- PGID=1000
- TZ=Etc/UTC
# Omit LIDARR_MEDIA_IO_PARALLELISM on fast local storage (max throughput).
# - LIDARR_MEDIA_IO_PARALLELISM=2 # NFS / slow disk — cap concurrent work
When to set it
- Fast local RAID / SSD: omit the variable (matches the first multithread fork).
- NFS or network filesystem: start with
2(or1) if scans overwhelm the host.
Implementation reference
src/NzbDrone.Common/MediaImportParallelism.cs.
Relationship to upstream
Behavior outside scan/import parallelism matches your chosen base (e.g. nightly image + overlaid build). For upstream docs and support channels, see Lidarr and the Servarr wiki.