MirrorService

This service enables your instance to mirror the public data of other SemApps instances. Data will be cached in a named graph and will be kept updated through ActivityPub.

Dependencies

• ActivityPubService
• LdpService
• WebfingerService

Sub-services

• SynchronizerService

Usage

const { MirrorService } = require('@semapps/sync');

module.exports = {
  mixins: [MirrorService],
  settings: {
    graphName: 'http://semapps.org/mirror',
    servers: ['https://otherserver.com'] // Other servers you want to mirror
  }
};

Dataset migration

If you were running a previous version of Jena Fuseki (before July 2022), you will need to migrate your dataset(s) configuration(s). First remove the current version of the docker image:

docker image rm -f semapps/jena-fuseki-webacl

Then follow the guide on dataset migration here.

Settings

Property	Type	Default	Description
graphName	String	"http://semapps.org/mirror"	Named graph where mirrored data are stored. If you change this value, you should also change the mirrorGraphName settings of the LdpService
servers	Array		List of servers URLs you want to mirror on start

Actions

The following service actions are available:

mirror

Download the public data of the server and insert them into the local mirror graph. Then follow the relay actor of the server to be kept updated of changes. If the relay actor is already being followed, an error will be returned. This action is automatically called on start if you provide the servers setting.

Parameters

Property	Type	Default	Description
serverUrl	string	required	URL of the server to mirror

Return

The URL of the remote relay actor.

LDP containers PATCH

When attaching a remote resource to a local LDP container with the PATCH method, if the remote server has not been mirrored yet locally, the MirrorService will mirror only that resource.

It will then periodically refresh that resource's data (using a simple fetch on the LDP resource) to keep it in sync with the remote server.

If the remote server is mirrored, then the resource will be kept up-to-date thanks to the ActivityPub activities sent by the relay actors.

This feature is thus independent of the mirror service and is always active when the LDP service is running.