Re: [gentoo-dev] [GLEP] Web Application Installation

[Robin H.Johnson]

On Sun, Aug 03, 2003 at 02:50:11AM +1000, Troy Dack wrote:
> Definitions
> ===========
*Web Application Instance*
  An apparent install of the Web Application that is served up via the
  webserver. There may be any number of instances per Web Application.
  This is a major use for web applications. Our Gentoo Zope setup
  already provides instances and can be used for some concepts on this
  matter.
*Web Application Setup Program*
  A script similar in function to zope-config that sets up instances.

> Rationale
> =========
2b. Web Application must be slotted by their major version numbers to
   further avoid downtime when true configuration changes are required.
6. It should be easily possible to have multiple instances of a web
   application without any duplication of source files.
7. It should be immediately apparent how to control instances of a web
   application.

> 2. Application Location
> -----------------------
> 	* for files to be served to clients::
> 		/usr/share/webapps/<application>/files/
Why the /files/ on the end, why not just leave it out?
Also, for compatibility and ease of upgrade (stay with me on this until
later) the actual install location should have several symlinks to it,
so that instances can change their version by updating a symlink,
instead of having to re-write their .htaccess files.
As such, we have the package actually installed at with it's full
version string, and a symlink with it's major version as the SLOT value
present.
/usr/share/webapps/${PF}
/usr/share/webapps/${PN}-${SLOT}

> 	* for documentation files (not served to clients)::
> 		/usr/share/doc/webapps/<application>/
What is different about this documentation compared to any existing
package documentation in /usr/share/doc/${PF}/ ?
Care must also be taken here as many web-apps ship documentation that is
referenced from inside the application as help, so should be installed
in such a location that it is still accessible.

> 3. Application Configuration
> ----------------------------
> 	* install configuration files in::
> 		/etc/webapps/<application>/
First the initial copy of the configuration files, eg their base setup
for Gentoo should be installed to a directory (the _default name could
be changed):
/etc/webapps/${PN}-${SLOT}/_default/

As needed, the webapp setup program copies and modifies the contents of
the default settings for each instance.
/etc/webapps/${PN}-${SLOT}/${INSTANCENAME}/

> 	* Apache configuration directives:
> 		- install a sample file in::
> 			/usr/share/doc/webapps/<application>/conf/
> 		  the ebuild should inform the user how to include this
> 		  information in their Apache configuration.
See my notes about documentation install location on this.

> 	  	- alternatively the configuration directives could be placed in::
> 			/etc/apache{1,2}/conf/webapps/<application>
> 		  this directory and the files in it should be included by the
> 		  main Apache configuration file.
The webapp setup program should create these as needed, possibly:
/etc/apache{1,2}/conf/webapps/${PN}-${SLOT}/${INSTANCENAME}.conf

> 4. Application Permissions
> --------------------------
No changes needed here at all.

5. Instances of Web Applications
--------------------------------
In a similar vein to Gentoo's Zope scripts, namely zope-config, we
should be able to have multiple instances of a single web application
without duplicating all of the files.

This also allows system administrators to control where web applications
will appear on their system, as well as to customize a file in a single
instance of a web application without effecting the original material.

webapp-config ${PN}-${SLOT} ${INSTANCENAME} \
/home/httpd/htdocs/..some-path-where-admin-wants-it.. (more options)
(or zope-config has a ncurses interface for this IIRC)

This is easily acheived thru use of Apache configuration directivies and symlinks.
For PHP instances, see http://tavi.sourceforge.net/VirtualHosts as for
some details.

The primary details here is that to the web-application, it appears that
all of it's configuration and files are in the instance directory, but
the files are physicalled located elsewhere.

> Implementation
> ==============
> Max Kalika <max@g.o> stated that he has a preliminary eclass that
> implements a good deal of this GLEP.
I've also got some experience with setting up instances of web
applications already as I have needed them for work. Previously I was
doing it by hand, but I am willing to be the main author of the tools
needed.

> Backwards Compatibility
> =======================
> There may be some issues regarding compatibility with existing installs of
> web applications.  This is particularly true if the default Document Root is
> moved from what is accepted as the current standard (/home/httpd).
There will with a doubt be very little backwards compatibility between
installs, however as the old /home/httpd/htdocs/${PN} is not being
overwritten, this allows admins time to migrate.

> Credits
> =======
Robin Johnson <robbat2@g.o> also make several initial comments on
the mailing lists as to web applications and instancing.

-- 
Robin Hugh Johnson
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