The Mercure Protocol

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Last updated 2018-10-11
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Network Working Group                                         K. Dunglas
Intended status: Informational                           11 October 2018
Expires: 14 April 2019

                          The Mercure Protocol


   Mercure is a protocol allowing to push data updates to web browsers
   and other HTTP clients in a fast, reliable and battery-efficient way.
   It is especially useful to publish real-time updates of resources
   served through web APIs, to reactive web and mobile apps.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 14 April 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Terminology
   2.  Discovery
   3.  Subscriptions
   4.  Hub
   5.  Authorization
   6.  Re-Connection and State Reconciliation
   7.  Encryption
   8.  References
       8.1.  Normative References
       8.2.  Informative References
   Author's Address

1.  Terminology

   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [RFC2119].

   *  Topic: An HTTP [RFC7230] or HTTPS [RFC2818] topic URL.  The unit
      to which one can subscribe to changes.

   *  Publisher: An owner of a topic.  Notifies the hub when the topic
      feed has been updated.  As in almost all pubsub systems, the
      publisher is unaware of the subscribers, if any.  Other pubsub
      systems might call the publisher the "source".  Typically a
      website or a web API.

   *  Subscriber: A client application that subscribes to real-time
      updates of topics (typically a Progressive Web App or a Mobile

   *  Hub: A server that handles subscription requests and distributes
      the content to subscribers when the corresponding topics have been
      updated (a Hub implementation is provided in this repository).
      Any hub MAY implement its own policies on who can use it.

2.  Discovery

   The publisher SHOULD advertises the URL of one or more hubs to the
   subscriber, allowing it to receive live updates when topics are
   updated.  If more than one hub URL is specified, it is expected that
   the publisher notifies each hub, so the subscriber MAY subscribe to
   one or more of them.

   The publisher SHOULD include at least one Link Header [RFC5988] with
   "rel=mercure" (a hub link header).  The target URL of these links
   MUST be a hub implementing the Mercure protocol.

   Note: this relation type has not been registered yet [RFC5988].
   During the meantime, the relation type "" can
   be used instead.

   The publisher MAY provide the following target attributes in the Link

   *  "last-event-id": the globally unique identifier of the last event
      dispatched by the publisher at the time of the generation of this
      resource.  If provided, it MUST be passed to the hub through a
      query parameter called "Last-Event-ID" and will be used to ensure
      that possible updates having been made during between the resource
      generation time and the connection to the hub are not lost.  See
      section #Re-Connection-and-State-Reconciliation).  If this
      attribute is provided, the publisher MUST always set the "id"
      parameter when sending updates to the hub.

   *  "content-type": the content type of the updates that will pushed
      by the hub.  If omited, the subscriber MUST assume that the
      content type will be the same than the one of the original
      resource.  Setting the "content-type" attribute is especially
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