Clarification about "farm" term and "install on farm"

Help / Discuss
#1

I always tought that the term “farm” should be associated with a single XWiki instance where multiple subwikis are created.
This probably comes from reading Multi-tenancy (XWiki.org) during installation.

I remember having seen the same term used for another setup (several XWiki instances running on the same server), but I can’t find where, so I cannot be sure; it could have been in Wiki hosting service - Wikipedia.

I just found this comment on an old thread: What does "on farm" mean? - #4 by vmassol where he mentions independent wikis.

Moreover, when addressing some issues while installing some extensions, I have been told not to use Install on farm Numbered Content extension installation - #17 by tmortagne

So this is a request for clarification about the term on farm and how extension installation should be carried over when we have a single XWiki installation with several subwikis - and extensions should be installed on each of them, both for already existing subwikis and for those created after an extension has been installed (if that’s possible of course).

Multiple wikis terminology
#2

The “farm” means the whole XWiki instance, whatever the number of wikis or anything else. For Extension Manager, it’s an abstraction level lower than the wikis. But this term is only used in the UI, in the code we talk about the root namespace from which each wiki namespace (and other namespaces, like users, spaces, etc.) inherits. So something installed at root namespace level is supposed to be available in each namespace too, for Java classes it means being registered in a root classloader from which each classloader associated to a specific namespace classloader inherit, but for a XAR extension you cannot technically do the same thing (there is no concept of page inheritance from the main wiki to a subwiki) so we “emulate” this by saving the pages of the extension in every wiki.

What @vmassol is mentioning here is not what the term “farm” means (it always means the XWiki instance and everything in it) but in which use case it’s used and here he is mentioning the myxwiki.org use case where a farm of wikis is a set of visually independent wikis (they are not independent at all technically, it just how things are presented to the basic users).

I mentioned extensions of type XAR and not extensions in general. And as I said, the problem is more for extensions which depends on standard extensions (which is very often the case for XAR extensions) because right now standard flavors is designed to be installed at a specific wiki level and forcing some of its parts to be moved at farm level would make upgrades less seamless.

#3

Thanks. I’ve opened a new thread at Multiple wikis terminology

#4

Oh, I completely overlooked that part of your other post; I never noticed there are several kinds of extensions, though looking at a bunch of the one already installed it seems the majority of them is in XAR format.

I guess this thread could be kept for specific reports?

I.e.: I was upgrading from 14.6 to 14.10.5 today and the wizard showed this for the Standard Flavor:

immagine

Maybe - but this is just me thinking - the wizard should only offer to Upgrade (or Upgrade on farm), but not Install, since this is the Extensions update step.

#5

I was thinking the same thing today while upgrading from 15.1. to 15.2: especially in the context of the XWiki Standard Flavor, it is really confusing to have the option there. And what about the other dependencies? Should I install them on the whole farm or is the main wiki enough?

#6

@tmortagne should know better. I guess this is to transform an extension installed only on the current wiki, so that the new version is installed for all wikis. I agree it’s not easy to understand and should be improved. I’m not even sure it does what I think it does…