casualoffice/calc repository overview

⁠OpenCalc collaboration server

The server that lets several people edit one spreadsheet at once. It orders operations, relays them, and hands the document back to whoever is storing it.

Alpha. The engine, editor, SDK and collaboration are live and exercised by two real browsers on every push. Operationally it is younger than that: there is no Helm chart yet, and Redis is a single node.

⁠Run it

docker run -p 8443:8443 \
  -e OPENCALC_SHARED_SECRET="a secret of at least 16 bytes" \
  -e OPENCALC_ALLOWED_HOSTS="files.example.com" \
  casualoffice/calc

It is a collaboration server, not a file store: it fetches each document from your own host over a URL carried in a signed token, and saves it back the same way. OPENCALC_ALLOWED_HOSTS is the list of hosts it may fetch from — compared with the port stripped, so files.example.com, not files.example.com:443.

For a whole stack — editor, storage, proxy — see the compose file in the repository.

⁠What it costs

Measured, not estimated: an idle node is about 6.6 MB, and each open document costs roughly 190 KB on top of its cells at three editors. Cells are about 84 bytes each. So:

RAM ≈ documents × (cells × 84 bytes + 190 KB) × 1.2

At 150 concurrent editors across 50 documents: 15.9 MB resident, every edit acknowledged, p50 18 µs. The 190 KB matters more than it looks — for a 1 000-cell sheet it is 70% of the cost, so a deployment of many small documents is sized by document count, not by cell count.

There is no cap on documents or people. A node admits work until its memory is short, and stops at 85% of its container's limit — reaching the ceiling is an OOM kill, and that takes every document on the node including unsaved work.

⁠Settings worth knowing

Full list: docs/65-RUNNING-IT.md in the repository.

⁠Tags

X.Y.Z is immutable. latest moves, and never to a prerelease. Images are built for linux/amd64 and linux/arm64, and carry a build provenance attestation naming the repository, workflow and commit that produced them.

⁠Source and licence

https://github.com/CasualOffice/opencalc⁠ — Apache-2.0.