Docs menu

How it works

slowhub

What the hub does for you: it runs your slowapps on time, keeps their latest cards, and holds each screen's layout and preferences.

slowhub is the hub. It runs your slowapps, keeps the latest cards from each, and hands them to your screens. It also holds the settings that belong to a screen: its layout and its preferences.

The same software runs everywhere: on a Slowboard 1085, where it shares the board with the display program, on a Linux machine of your own with enough memory, and, soon, as a hosted hub run by us. One hub can serve several screens, and each screen gets its cards from exactly one hub.

What it does

  • Runs your apps at the right time. Each screen tells the hub which feeds it shows and when it next needs them. The hub works out when to start each app so its cards are ready a little before that time, and starts the longest-running ones first.
  • Keeps the apps in their lanes. Each app runs in a container with only the grants it declared: its memory, its network access, its secrets, its own data folder. The hub starts an app only when there is memory for it, so a large map render waits rather than crowding out everything else.
  • Checks and stores cards. Every card is checked for size and colours before a screen sees it. Identical cards are stored once.
  • Holds each screen’s layout and preferences. Which feed goes in which slot, how often the screen updates, its active and quiet hours. See Layout and preferences.
  • Passes answers back. When someone answers a question on a screen, the hub hands the answer to the app that asked it.

When things go wrong

  • An app fails. The screen keeps the app’s last cards. A temporary failure, such as a network error, is retried with a growing delay. A missing setting or secret is shown on the hub and isn’t retried until it changes.
  • The internet is down. The hub doesn’t start apps that need the network until it is back, and the screen keeps showing what it has.
  • The hub is down. The screen keeps showing its cards and the keys keep working. Answers wait on the screen’s side and are delivered when the hub returns.
  • The clock isn’t set yet. After a power cut, the hub waits for the time to be synced before running scheduled work.

Where it runs

On a Slowboard 1085, slowhub runs on the board as a background service for the user epaper, and the display program talks to it over a local socket. Elsewhere, slowd connects to the hub over the network with a token. See Install slowhub.

Next

Updates, now and then

A short note when there is a new board, a new slowapp, or kit news. Rarely more than one a month.