Locationmap as config system

[Ross Gardler <ro...@gardler.org>]

Those who were in Stuttgart will remember (I hope) a discussion about 
the future of our config system. Anil took the time to go through the 
podcast of the session and pull out the conclusions [1]

One of the main points in this discussion was that we need to move the 
config stuff out of forrest.xconf since a change to that file requires 
that the server be restarted, not a good thing in a production environment.

In addition, having the config in forrest.xconf prevents Forrest from 
hosting multiple sites.

My proposal at the time was to use the locationmap. At the time it was 
not possible because LMs could not mount other LMs. However, Tim has 
sorted this out for us, so we can start thinking about this move. Since 
Thorsten is also moving views to use the LM everything should be in 
place soon.

Now that I have started to convert our sitemaps to use the LM I hope 
that it is a little clearer how this would work. Basically, the idea is 
that Forrest provides the default configuration in its LM, individual 
projects can then override these settings in their own LM.

For example, we currently have:

<map:parameter name="config-file" value="{project:skinconf}"/>

Where project:skinconf is set in forrest.xconf (via forrest.properties).

With my current work on the LM we will have:

<map:parameter name="config-file" value="{lm:project.skinconf}"/>

where lm:project.skinconf is set in locationmap.xml.

In this first stage we still use {project:skinconf} in the LM, so we 
gain nothing. However, in the next stage I intend to replace this with 
the actual path (i.e. what is currently in default-forrest.properties

If a project wants to change the location of the skinconf file they can 
do so in the LM rather than in forrest.properties. Thus, a change does 
not require a server restart.

What is missing?
================

Multiple Sites
--------------

Forrest needs to be able to host multiple sites, each with their own 
configuration. We need to extend the locationmap mounting code to allow 
a specific project file to be mounted. This will be dependant on the 
request. Since the LM has access to the request object, this shouldn't 
be too hard to do.

None Location configuration
---------------------------

Some configuration has nothing to do with file location, for example, 
the name of the theme to use. We need to consider where this 
configuration will go. I've not thought hard about this issue yet, but 
my guts tell me that *all* parameters are only inportant to Forrest with 
respect to a location, for example, the project.theme value is used to 
build a path to retrieve theme related files.

If my guts are correct, we need to allow the locatonmap to have a 
variables section. These variables can then be used later in the locator 
  to define a path.

Even if my guts are incorrect, I think we still need this variable 
feature since some paths will appear in multiple locators  (i.e. 
content/documentation)

Thoughts?

Ross

Re: Locationmap as config system

[David Crossley <cr...@apache.org>]

Ross Gardler wrote:
> 
> Now that I have started to convert our sitemaps to use the LM I hope 
> that it is a little clearer how this would work. Basically, the idea is 
> that Forrest provides the default configuration in its LM, individual 
> projects can then override these settings in their own LM.

I was already thinking in this direction too.

Forrest provides known default locations using a
well-defined naming convention. This means a reliable
infrastructure that just works out of the box.
Tweak it and override if you want.

The remark by Berin on Cocoon dev emphasises the beauty
of "convention over configuration":
http://marc.theaimsgroup.com/?l=xml-cocoon-dev&m=112812292724833

-David

Re: Locationmap as config system

[David Crossley <cr...@apache.org>]

Ross Gardler wrote:
> Those who were in Stuttgart will remember (I hope) a discussion about 
> the future of our config system. Anil took the time to go through the 
> podcast of the session and pull out the conclusions [1]

http://marc.theaimsgroup.com/?t=112265719400005
Re: Config files

http://marc.theaimsgroup.com/?t=112299875300003
Re: Forrest Config

http://issues.apache.org/jira/browse/FOR-588
Design new configuration system

-David