mod_http_roster_admin

NOTE: THIS MODULE IS RELEASED UNDER THE MOZILLA PUBLIC LICENSE VERSION 2.

Normally the XMPP server will store and maintain the users’ contact rosters. This module lets you delegate roster management to an external service.

Prosody will make an HTTP request to fetch the roster from the external service. The service will need to notify Prosody whenever a user’s roster changes, so that Prosody can fetch a new roster for that user.

Configuring this module

This module relies on mod_storage_memory and mod_block_subscriptions.

In .parts/prosody/etc/prosody/prosody.cfg.lua, where your particular VirtualHost is being configured, add the following:

modules_enabled = {
    "http_roster_admin",
    "block_subscriptions",
    "storage_memory",
    "http_files"
}
modules_disabled = {
     -- Prosody will get the roster from the backend app,
     -- so we disable the default roster module.
    "roster"
}
storage = { roster = "memory" }
http_roster_url = "http://localhost/contacts/%s" -- %s will be replaced by an URL-encoded username

The http_roster_url parameter needs to be configured to point to the URL in the backend application which returns users’ contacts rosters.

In this URL, the pattern %s is replaced by an URL-encoded username.

When the user john then connects to Prosody, and http_roster_url is set to “http://app.example.org/contacts/%s”, then Prosody will make a GET request to http://app.example.org/contacts/john

Protocol

Fetching rosters (Prosody to web app)

Prosody considers the web application to always hold the most accurate and up-to-date version of the user’s roster. When a user first connects, Prosody fetches the roster from the web application and caches it internally.

Prosody will make a GET request to the URL specified in Prosody’s configuration parameter ‘http_roster_url’. In this URL, the pattern ‘%s’ is replaced by an URL-encoded username.

For example, when the user ‘john’ connects to Prosody, and http_roster_url is set to “http://app.example.com/contacts/%s”, Prosody will make a GET request to “http://app.example.com/contacts/john”.

The web app must return a JSON object, where each key is the JID of a contact, and the corresponding value is data about that contact.

If the user ‘john’ has friends ‘marie’ and ‘michael’, the web app would return a HTTP ‘200 OK’ response with the following contents:

{
    "marie@example.com": {
        "name": "Marie"
    },

    "michael@example.com": {
        "name": "Michael"
    }
}

Notifying Prosody of roster changes

The external service needs to notify Prosody whenever a user’s roster changes. To do this, it must make an HTTP POST request to either:

• http://localhost:5280/roster_admin/refresh
• https://localhost:5281/roster_admin/refresh

Make sure that the “http_files” module is enabled in Prosody’s configuration, for the above URLs to served.

Ports 5280/5281 can be firewalled and the web server (i.e. Apache or Nginx) can be configured to reverse proxy those URLs to for example https://example.org/http-bind.

The contents of the POST should be a JSON encoded array of usernames whose rosters have changed.

For example, if user ‘john’ became friends with ‘aaron’, both john’s contact list and aaron’s contact lists have changed:

["john", "aaron"]

When the operation is complete Prosody will reply with a summary of the operation - a JSON object containing:

• status: either “ok” (success) or “error” (operation completely failed)
• message: A human-readable message (for logging and debugging purposes)
• updated: The number of rosters successfully updated
• errors: The number of rosters that failed to update

Example:

{
    "status":  "ok",
    "message": "roster update complete",
    "updated": 2,
    "errors":  0
}

Prosody may also return status codes 400 or 500 in case of errors (such as a missing/malformed body).

sudo prosodyctl install --server=https://modules.prosody.im/rocks/ mod_http_roster_admin