Changes between Initial Version and Version 1 of Obsolete/Development/Code/PerlNamespaces

Timestamp:

Mar 20, 2010, 10:28:53 PM (16 years ago)

Author:

loomis

Comment:

--

Obsolete/Development/Code/PerlNamespaces

@@ +1 @@
+[[TracNav]]
+
+== 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.
+