litsync — incremental PubMed + PMC + FDA + ClinicalTrials.gov mirror

A modern, daily-runnable CLI for mirroring bulk biomedical datasets. It tracks every file in a SQLite state DB so re-runs do the minimum work: already-verified immutable files are skipped with no network request beyond the directory/manifest listing.

Documentation: https://takshan.github.io/LitSync

Install

pip install -e .

Or use the Makefile:

make install
make dev

Quick start

litsync --data-root /data/literature --email you@institute.org

Common options:

litsync --data-root /data/literature --email you@institute.org \
  --sources pubmed pmc fda clinicaltrials \
  --fda-endpoints drug/event drug/label

--sources pubmed pmc fda clinicaltrials   # which corpora (default: all four)
--fda-endpoints drug/event drug/label     # default: all openFDA endpoints
--pmc-groups oa_comm oa_noncomm oa_other
--pmc-formats xml txt                     # default: xml
--workers 4                               # concurrent downloads (keep modest; be polite)
--dry-run                                 # plan only, download nothing
--reverify                                # re-download local files (integrity audit)
--prune                                   # delete local files no longer on the server
--count-articles                          # count articles in already-downloaded files (no network)
--no-rich                                 # disable Rich progress bars / tables

On-disk layout

/data/literature/
  pubmed/baseline/                    pubmed26nXXXX.xml.gz (+ .md5 verified)
  pubmed/updatefiles/                 daily citation deltas
  pmc/oa_bulk/<group>/<fmt>/          baseline + dated incremental .tar.gz
  pmc/oa_file_list.csv                PMCID <-> PMID id map
  fda/<category>/<endpoint>/          openFDA bulk snapshot zips + extracted JSON
  clinicaltrials/ctg-public-xml.zip   ClinicalTrials.gov full XML dump
  clinicaltrials/ctg-public-xml/      extracted study XML files
  _state/state.sqlite                 file ledger (status, size, mtime, md5, etag, attempts)
  _state/logs/                        dated run logs
  _state/litsync.lock                 run lock (prevents overlapping cron runs)

Cron (daily 02:30)

30 2 * * *  /path/to/venv/bin/litsync --data-root /data/literature --email you@institute.org >> /data/literature/_state/cron.log 2>&1

Extract corpus to sharded JSONL

litsync-extract --data-root /data/literature --out /data/corpus \
  --sources pubmed pmc fda clinicaltrials

Or with Make:

make extract DATA_ROOT=/data/literature CORPUS_OUT=/data/corpus
make extract-test DATA_ROOT=/data/literature

Integrity model

• PubMed: every .xml.gz is verified against its NCBI .md5 sidecar.
• PMC: bulk packages have no md5 sidecar, so they are verified by Content-Length and an ETag is recorded for change detection.
• openFDA / ClinicalTrials.gov: these sources publish full snapshots. The downloader detects changed snapshots via ETag / Last-Modified / Content-Length and only re-downloads when the snapshot changes. When a snapshot changes it is extracted again next to the zip file.
• Downloads are atomic (.part -> rename) and resumable via HTTP Range.
• Exit code is non-zero if any file failed, so cron/monitoring can alert.

Notes on sources

• openFDA bulk data is zipped JSON. The manifest is fetched from https://api.fda.gov/download.json. Each endpoint partition becomes one downloaded/extracted unit.
• ClinicalTrials.gov bulk data is the full public XML dump from https://clinicaltrials.gov/api/legacy/public-xml?format=zip. One XML file per study.
• Both sources are snapshots, not daily deltas. Daily runs are still cheap because unchanged snapshots are skipped; changed snapshots are replaced in full.