Core Concepts

These are the building blocks every NoLag app is made of. Read them in order for a full mental model, or jump straight to the one you need.

Everything here describes the open-source stack: the kraken broker, optionally backed by @nolag/core for authorization, and the client SDKs. Where a behaviour depends on which auth backend you run (kraken's static auth.json file or @nolag/core), the page says so.

In this section

• Hierarchy explains how projects, apps, rooms and topics fit together, and where access scopes slot in.
• Topics and Pub/Sub covers the publish-subscribe model, how topics are addressed, the message shape, echo, retained messages and load-balanced subscriptions.
• Rooms explains why rooms exist, how they come into being, and public versus private rooms.
• Access Control describes topic permissions, open and restricted apps, and room grants.
• Presence tracks who is connected to a room, with join, leave and update events.
• Lobbies observe presence across many rooms at once, with the limits of the current release.
• Filters narrow delivery within a topic to specific entities.
• Quality of Service covers what the QoS levels and acknowledgements do, and what kraken does not guarantee.
• Webhooks call your HTTP endpoints when an actor subscribes (hydration) or publishes (trigger).

For tenant isolation within one deployment, see Access Scopes. For the frames on the wire, see the Wire Protocol.

Next

Ready to build? Follow the Quick Start to run kraken locally, or read Self-Hosting to choose a setup.