On 08/24/2014 04:37 PM, Nico Kadel-Garcia wrote:
Installation scripting is not the only source of the problem. Perl
modules have been prone to this.
* Perl module A requires perl module B.
* Perl module B requires perl module C.
* One small script or macro in module C requires one small script from
module A. It may not even be a critical component of C, and may be
easily segregated, but suddenly there is a circular dependency.
The vortex enters when the author of module B updates to a new
dependency or build dependency that is not in the current version of
C, and C introduces a new dependency on A but it's based on an older
version of A, that has since discarded that macro due to a code
cleanup. Hilarity ensues.....
The underlying point is that it's sometimes very helpful to split
upstream packages to smaller, individual components, precisely to
segregate these dependencies. It's especially useful with Perl
modules. I have.... old stories about the mod_perl updates back when
HTTPD 2.x was first released and mod_perl compatibility became kind of
nutty.
Or we can wait for F21, which will have weak dependencies in RPM. And I anticipate that weak dependencies will break a
lot of circles.
--
Miroslav Suchy, RHCE, RHCDS
Red Hat, Senior Software Engineer, #brno, #devexp, #fedora-buildsys
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