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Mercure Channel Binding v0.1.0 ​

The Mercure channel binding defines how an AsyncAPI channel maps to a Mercure topic. In Mercure, a topic is a simple URL to which updates are published.

Overview ​

The presence of this binding on a channel object indicates that the channel's address is a Mercure topic URL. Clients subscribe to this URL to receive real-time updates, and publishers target this URL to send messages. As of v0.1.0, this binding is a placeholder and has no configurable properties. Its purpose is purely informational.

Channel Properties ​

PropertyTypeRequiredDescription
bindingVersionstringNoBinding version (defaults to 0.1.0)

Mercure Channel Concepts ​

Topics as URLs ​

Unlike message brokers that use abstract topic strings, Mercure uses standard URLs as topic identifiers. This leverages the existing infrastructure of the web and makes topics discoverable. Any valid URL can be a topic.

Topic Selectors ​

Mercure supports subscribing to multiple topics at once using topic selectors, which are URI Templates (RFC 6570). This is a powerful feature for clients that need to listen to a dynamic set of resources.

For example, a client could subscribe to https://example.com/users/{id} to receive updates for all users.

Examples ​

Static Topic URL ​

Defines a channel that maps to a single, static Mercure topic.

yaml
channels:
  productUpdates:
    address: 'https://example.com/products/123/updates'
    bindings:
      mercure:
        bindingVersion: '0.1.0'

Dynamic Topic with Parameters ​

Defines a channel that uses a parameter to represent a collection of related topics.

yaml
channels:
  userSpecificNotifications:
    address: 'https://example.com/users/{userId}/notifications'
    parameters:
      userId:
        description: The unique ID of the user.
        schema:
          type: string
    bindings:
      mercure:
        bindingVersion: '0.1.0'

Changelog ​

Version 0.1.0 ​

  • Initial release of the Mercure channel binding.
  • The binding is a placeholder with no specific properties, serving to identify the channel as a Mercure topic.