= Quattor-specific Perl Namespaces =
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== Current State ==

As of early 2009, the various Quattor tools use the following PERL namespaces for modules:

''EDG::WP4::CCM::'' The namespace used for accessing the locally installed configuration profile (whether it's for the local node, or downloaded in order to discover configuration of a foreign node).

''NCM::'' Utility libraries used by dispatcher components, and by the dispatcher itself. Under this namespace is a subnamespace "Components" - all quattor ncm components are accessed via this namespace. For example, NCM::Component::filecopy is the namespace used by the "filecopy" component.

''NCD::'' For the Node Configuration Dispatcher. Only used by the dispatcher itself.

''SPM::'' For SPMA. Note that the perl namespace is only "SPM" and not "SPMA".

''CAF::'' The Common Application Framework

''LC::'' Lionel Cons' utilities for interacting with the system with extra caution. Used/wrapped extensively by the CAF toolset.

== Proposal ==

 * All quattor specific modules should move to a new Quattor:: namespace. 
 * The "CCM" acronym can be renamed as "Profile".
 * The NCM and NCD namespaces could be merged.
 * The CAF namespace should be merged into the Quattor toplevel namespace. In other words, "perl-CAF" package should become "perl-Quattor", since it provides the base libraries for driving Quattor.
 * The LC package should be included within CAF/perl-Quattor. An explicit fork of the LC codebase.

This would give the following mapping:

|| '''From''' || '''To''' || '''Examples'''
||EDG::WP4::CCM:: || Quattor::Profile:: ||Quattor::Profile::Element, Quattor::Profile::CacheManager
||NCM:: || Quattor::Config:: ||Quattor::Config::Component::filecopy, Quattor::Config::Check::File
||NCD:: ||Quattor::Config:: ||Quattor::Config::ComponentProxy
||SPM:: ||Quattor::SPMA:: ||Quattor::SPMA::Package
||CAF:: || Quattor:: ||Quattor::Lock, Quattor::Log, Quattor::Process, Quattor::Reporter, etc.
||LC:: ||Quattor:: || Quattor::Check, Quattor::File, Quattor::Stat

== Implementation Plan ==

This involves changing almost every bit of perl there is.

=== SPMA ===

This can be changed at any time. The library is purely used by the "spma" tool itself.

=== EDG::WP4::CCM, a.k.a. the 'ccm' tools ===

The EDG::WP4::CCM:: namespace is defined by the "ccm" package and consumed by "ncm-query", "ncm-ncd", "aii" and some of the components, therefore care must be taken in changing this namespace. Possibly the trampoline mechanism described below could be used.

=== Components ===

Significantly, every component places itself into the namespace with a header that says something along the lines of "package NCM::Component::@COMP@". Therefore, the dispatcher (ncm-ncd) needs to support *both* namespaces (with a priority ordering biased towards the new name). Since the namespace is only used within ncm-ncd, this means that ncm-ncd has to be changed first before any components. From that point on, components can change at whatever pace they want.

== Namespace Compatibility Mechanism ==

You can make a compatability later by playing tricks like the following:
{{{
 package EDG::WP4::CCM::Element;
 use base 'Quattor::Legacy::Factory';
}}}
Where the legacy factory looks like:
{{{
 package Quattor::Legacy::Factory;
 use Carp; 
 our $mapping = {
     "EDG::WP4::CCM" => "Quattor::Profile",
 };
 sub new {
     my ($class) = shift;
     if (ref $class) {
         return $class->SUPER::new(@_);
     }
     # find the best match in the mapping
     my $best  = ""
     foreach my $maybe (%$mapping) {
         if ($class =~ /^$maybe/ && length($class) > $best) {
             $best = $maybe;
         }
     }
     if (!$best) {
         Carp::confess("legacy support requested for $class, which is unsupported");
     }
     my $final = $mapping->{$best};
     if ($class =~ /${best}::(.*)/)) {
         $final .= "::$1";
     }
     print STDERR "WARNING: Quattor legacy code causing conversion of $class to $final\n";
     eval "require $final";
     if ($@) {
         Carp::confess("legacy support of $class failed: $@");
     }
     $final->new(@_);
 }
}}}

=== Concerns ===

Any code that uses the "isa()" method will need to be modified. The exception handling code within ncm-ncd might also need to change.