Re: Apache should never be a mandatory dependency

[Jonathan Perkin <jperkin%joyent.com@localhost>]

* On 2014-05-18 at 05:06 BST, Alistair Crooks wrote:

> What I would suggest is a "generic" style of package, let's call it
> 
>       pkgsrc/metapackages/webserver
> 
> It's not just webservers this can be used for - I can think of editors
> (and, within editors, sub classes of vi, emacs and other packages),
> browsers, versions of scheme, common lisp, shells, etc.
> 
> Anyway, to get back to the worked example - this will make sure a
> webserver is installed.  It can take preferences from a setting in
> /etc/mk.conf (on a per-platform basis), of the form
> 
>       GENERIC.webserver=      apache22
> 
> If no preference is given at package installation time, it will select
> the default one for you.
> 
> So the line in the webserver pkgsrc entry Makefile would look like:
> 
>       .include "../../mk/bsd.prefs.mk"
> 
>       .if defined(GENERIC.webserver)
>       _WEBSERVER=${GENERIC.webserver}
>       .else
>       _WEBSERVER=${_DEFAULT_GENERIC_WEBSERVER}
>       .endif
> 
>       DEPENDS+=       
> {bozohttpd>=20140201,apache22>=2.2.27,apache24>=2.4.9,nginx>=1.6.0}:../../www/${DEFAULT_GENERIC_WEBSERVER}
> 
> Seems simple to me, and, in lieu of any other mechanism within pkgsrc,
> should work. I'm less chuffed with the version numbers there, but I
> wonder if there's some way to generalise them.

We use this type of mechanism at Joyent to support all the various
MySQL forks we've added.  It's ... not great.

Users regularly get confused because some random package happens to
need to pull in a MySQL client library, and due to the DEPENDS
matching will pull in the first match, which is often not what they
want to use.  When they come later to install their preferred MySQL
server, they can't due to conflicts, and have to unwind the
installation back so that they start with their preferred version.

This is somewhat unavoidable due to hard dependencies on
libmysqlclient, which changes version between forks, so currently is a
necessity we have to put up with (and we produce specific images to
make it easier for users to pick their preferred option).

When the dependency is soft, like with a web server, then I would
definitely not want any of this getting in the way.  If people really
want it regardless, that's fine, but please can we have a global knob
to turn it off completely to save us having more diffs.

We're working to remove dependencies to make packages more flexible,
rather than the other way around.

Thanks,

-- 
Jonathan Perkin  -  Joyent, Inc.  -  www.joyent.com