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Mateu

Record presence

Status: ✅ Implemented · @Experimental

Intent

Section titled “Intent”

Two people open the same order. One changes the delivery date, the other the address, and the second save is refused (@Version already does that) — after the work is done. Presence warns before: a small line in the page header says “Ana is editing this record” on a warning tone, or “Bob is viewing it” when someone is only looking.

Solution

Section titled “Solution”

Turn it on for the app:

@UI("")
@App(presence = true)
public class Shell { … }

That is all. Every record page of the app — a CRUD record (view or edit), an EditableView, a YAML record page — takes part; nothing is declared per screen.

ConceptWhat Mateu uses
The recordits route (mount-relative; orders/7, orders/7/edit and orders/7/view are the same record) plus the page’s view class — no new id concept. A create page (…/new) is no record yet.
Whothe name of the identity the host framework authenticated (see security); a PrincipalResolver can make it a full name. An anonymous caller neither shows nor sees anyone.
Viewing / editingediting = the page holds unsaved changes (the same flag the unsaved-changes guard uses).
The apppresence of one app (base url + app class) never reaches another, nor another record.
Accessa record the caller may not open — its route’s access: refuses them, or its view is not a type the app exposes to them (class-level @EyesOnly) — is answered with nothing: they neither see who is there nor show up there.

On the web, a page counts as a record page when its route has two or more segments (orders/7) — or, for a one-segment route (profile), when the page edits (it asks to confirm leaving with unsaved changes). A listing or a dashboard shows nobody.

How it travels

Section titled “How it travels”
  • Each record page reports itself with the app-level action _presence (viewing, editing or leave) every 10 s, and once more at once when it starts or stops editing. The answer lists the other people on the record — one entry per person, editing if any of their tabs edits; you are never in it.
  • The others hear the change at once through the app event stream — the same single _live-updates stream per browser that live header values use (one leader tab holds it and relays to the others). presence = true opens that stream even without liveUpdates.
  • A tab not seen for 30 s is gone: a closed tab disappears even when its leave never arrived.
  • When someone starts editing, it is announced to screen readers once, politely (“Ana started editing this record”).

A cluster

Section titled “A cluster”

Out of the box presence is kept in memory, per process — bounded: 10 000 open records, 50 copies per record, 50 per user; beyond a bound a new copy is simply not shown. Two users on different nodes do not see each other. Mateu ships UI only, so sharing it is an interface the app implements:

@Component
class RedisPresenceStore implements PresenceStore {
    public boolean touch(String scope, String record, PresenceMember member) { … }
    public void leave(String scope, String record, String principal, String tab) { … }
    public List<PresenceMember> members(String scope, String record, Instant seenAfter) { … }
    // optional: expire(...) when the store has no TTL of its own,
    //           onChange(...) to push changes at once (else they show on the next heartbeat)
}

In YAML

Section titled “In YAML”
type: AppShell
presence: true

C# and Python

Section titled “C# and Python”
[UI("")]
[App("Orders", Presence = true)]
public class Shell { }
// a shared store: services.AddSingleton<IPresenceStore, MyStore>();
@ui("")
@app("Orders", presence=True)
class Shell: ...
# a shared store: add_mateu(api, module, presence_store=MyStore())

Where it works

Section titled “Where it works”
  • Vaadin — a chip in the page header, under the title (mateu-presence-chip): avatars with initials and the line; a warning tone when someone edits.
  • React Native — a line above the record screen.
  • IntelliJ plugin / desktop app — a line in the page header; the editing state is reported on the heartbeat.
  • Redwood (Oracle VB) — not yet: the flag is on the wire, the renderer ignores it.
Section titled “Related”