cogAllow replicating pages and other data between different XWiki instances
TypeXAR
CategoryApplication
Developed by

Thomas Mortagne

Active Installs2
Rating
0 Votes
LicenseGNU Lesser General Public License 2.1

Installable with the Extension Manager

Description

The aim of this project is to make easy to share data between different XWiki instances and also expose as a demonstration the replication of wiki pages.

You can contribute translations for this application on https://l10n.xwiki.org/projects/xwiki-contrib/application-replication-default/.

This project is still very much in beta and the 1.0 version is planned for the beginning of 2022. The design and ideas of the future features and improvements can be found on Instances replication.

Current main limitations to be improved before 1.0 version:

  • there is currently not much security to make sure the sending instance really is what it's claiming to be, so better make sure only the expected IPs are allowed to access the replication endpoints (as in https://mydomain/xwiki/replication/*)

Linking instances

To start sharing messages between instances, you have to link those instances: this is done in the wiki administration -> Replication section.

admin.png

An instance will start by requesting another one using the URL leading to XWiki (for example https://mydomain.com/xwiki). This will make the current instance pop in the target instance admin as a "Requesting instance" which can then be accepted (or declined).

Page Replication

The project also provide a use case which exploit this data replication framework to replicate wiki pages between instances.

Standard controller

On each page, it's possible to control if the page alone or the page and its children should be replicated and with which instances.

You can configure this in the page administration.

pageadmin.png

Status

Below each page, you get information about the replication status of that page.

docextra.png

There are two levels of replication:

  • Everything: the whole page is replicated
  • Reference: only the reference of the page is replicated, meaning that an empty placeholder is created on the other instances

readonly.png

Implement a new type of replication

The replication framework distribute "replication messages". Those messages are composed of the following:

  • a unique identifier
  • the date/time at which it was created
  • the instance which is the initial source of the message
  • a message type associated with the data
  • custom binary data
  • custom map of metadata

There are two main entry points for custom replication implementations:

  • org.xwiki.contrib.replication.ReplicationSender: this component allows sending messages to specific (or all) registered instances
  • org.xwiki.contrib.replication.ReplicationReceiver: a component role to implement in order to receive all messages associated with the message type indicate as component hint

Limitations

Notifications replication

Notifications and notification preferences are not directly replicated currently.

But there are cases where you will get the same notifications on all instances (they are not technically replicated, but all instances appear to have created the same notifications on their own). In general, the instance in which a document is replicated behave as if the page was saved locally (except rare cases like, of course, not replicating back a page that was just received) so any page creation/modification/deleting which produce a notification locally will produce the same notification in the other instances too (provided the conditions are the same).

Here are such examples for page related notifications:

  • pages you explicitly follow on several instances: notifications preferences control for which page you want to receive notifications, so you will get notifications if an instance has preferences indicating that you follow a given page even if that page came from a replication message
  • auto watch: by default you automatically follow a page on which you made a major modification and same as for the previous point this will produce notifications preferences for a page exactly as if it was saved locally

Generic architecture

See Architecture.

Prerequisites & Installation Instructions

We recommend using the Extension Manager to install this extension (Make sure that the text "Installable with the Extension Manager" is displayed at the top right location on this page to know if this extension can be installed with the Extension Manager). Note that installing Extensions when being offline is currently not supported and you'd need to use some complex manual method.

You can also use the following manual method, which is useful if this extension cannot be installed with the Extension Manager or if you're using an old version of XWiki that doesn't have the Extension Manager:

  1. Log in the wiki with a user having Administration rights
  2. Go to the Administration page and select the Import category
  3. Follow the on-screen instructions to upload the downloaded XAR
  4. Click on the uploaded XAR and follow the instructions
  5. You'll also need to install all dependent Extensions that are not already installed in your wiki

XWiki needs to be restarted after the first install of the extension (it's providing a database table, which currently is only loaded at XWiki startup).

Release Notes

v0.13

v0.12

v0.11.1

v0.11

v0.10

v0.9

v0.8

v0.7

v0.6

v0.5

v0.4

v0.3

v0.2

v0.1

Dependencies

Dependencies for this extension (org.xwiki.contrib.replication:replication-ui 0.13):

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