Webhooks MQTT and iCal

Webhooks, MQTT & iCal

Beyond simple queries, the bridge can push your inventory into other systems — fire webhooks on changes, publish over MQTT, and serve a calendar feed. Each is a separate opt-in.

ℹ️ Note These are technical integrations, configured on the bridge itself rather than in Gubbins; this page explains what each is for, and the exact configuration is in the bridge README in the Gubbins repository. Webhooks are the exception — they have their own screen in Gubbins, and their own page: Webhooks.

Change events: webhooks & SSE

The bridge can emit change events — an item's stock went low, something was added, a loan came due. Two ways to consume them:

• Webhooks — a URL of your choosing is called when something happens, so another system can react. You set these up in Gubbins, on its own Webhooks screen; the bridge delivers them. That page covers events, filters, payloads, signing and the delivery log.
• SSE event stream — a live stream you can subscribe to for a running feed of changes, set up on the bridge.

Both are off until you enable them.

Lookup events

The bridge can also announce when a "where is…" question resolves — the question asked, what matched, and which locations it's in. That's what lets an automation light up the right bin as the answer is read back.

This one is different from every other event: the rest report something that changed in your inventory, whereas this reports something that was merely looked up. Because it publishes what someone searched for, it has its own separate switch and stays off even if you've enabled events generally — turning on change events never turns this on for you.

💡 Tip Repeated or rephrased questions are grouped together for a few seconds, so asking twice won't set the same automation off twice.

MQTT publishing & Home Assistant discovery

The bridge can publish to an MQTT broker — including summary topics like stock counts — and announce them via Home Assistant MQTT discovery, so they show up as entities automatically. Each location is published with its item count and its own custom fields alongside, so an automation can read something like "which light is above this shelf" straight off the location.

If you've turned on lookup events, a resolved "where is…" question is also published to its own topic, so a Node-RED flow or an MQTT trigger can act on the answer without the Home Assistant custom integration. That one is sent live only — it is never replayed to something that connects later, so an old question can't set an automation off.

⚠️ Heads-up — if you already had MQTT publishing switched on Locations' custom fields were added to what MQTT publishes, and they don't have a switch of their own — turning on MQTT publishing is what enables them. So if you'd already set MQTT up before this was added, your locations' field values start reaching your broker when you update, without you changing anything.

That's the intended behaviour, and it's your own broker. It's just worth a glance at what you've recorded on locations: all of a location's fields are published, and you can't hold one back while publishing the rest. If something there is genuinely sensitive, move it to the item, limit the topic with a broker rule, or leave MQTT publishing off. Fields on items are never published this way.

See Home Assistant integration.

Calendar feed (iCal)

The bridge serves a read-only iCalendar feed of Gubbins' time-bearing facts — loan due-backs, bookings, maintenance and warranty dates — that any calendar app can subscribe to. Your Gubbins deadlines then sit alongside the rest of your schedule, updating as your data changes.

💡 Tip The calendar feed is the easiest of these to use — subscribe to it from your phone or desktop calendar and every Gubbins due-date appears automatically, no automation required.

⚠️ Heads-up These surfaces can send your data outward (to a webhook target, an MQTT broker, a calendar service). Each is opt-in, reachable only with an API token whose owner has permission for it, and best kept to trusted destinations and your local network. See Privacy & security.

💡 Tip A calendar subscription carries its token in the URL, which is easier to leak than a normal request. Mint that one against an account whose role does little beyond read bookings — see Bridge API tokens.

Related pages

• Webhooks — setting up webhooks in Gubbins itself.
• Bridge overview and Running the bridge — the foundation.
• Home Assistant integration — MQTT discovery in context.
• Upcoming agenda — the in-app view of the same deadlines the iCal feed publishes.