Adding support for versions and freshness-checking

to the indirection layers.  This should hopefully
enable the different application models we need in
our different executables.

3 files changed, 50 insertions, 12 deletions

diff --git a/lib/puppet/indirector.rb b/lib/puppet/indirector.rb
index 7ceaa43e2..a2eb41763 100644
--- a/lib/puppet/indirector.rb
+++ b/lib/puppet/indirector.rb
@@ -62,6 +62,10 @@ module Puppet::Indirector
     end
 
     module InstanceMethods
+      # Make it easy for the model to set versions,
+      # which are used for caching and such.
+      attr_accessor :version
+
       # these become instance methods 
       def save(*args)
         self.class.indirection.save(self, *args)
diff --git a/lib/puppet/indirector/indirection.rb b/lib/puppet/indirector/indirection.rb
index 3a6284877..cd71c4d66 100644
--- a/lib/puppet/indirector/indirection.rb
+++ b/lib/puppet/indirector/indirection.rb
@@ -90,12 +90,18 @@ class Puppet::Indirector::Indirection
         end
     end
 
-    def find(*args)
-        terminus.find(*args)
+    def find(key, *args)
+        if cache? and terminus.fresh?(key, cache.version(key))
+            return cache.find(key, *args)
+        end
+        if result = terminus.find(key, *args)
+            result.version ||= Time.now.utc
+            cache.save(result, *args) if cache?
+            return result
+        end
     end
 
     def destroy(*args)
-        cache.destroy(*args) if cache?
         terminus.destroy(*args)
     end
 
@@ -104,9 +110,12 @@ class Puppet::Indirector::Indirection
     end
 
     # these become instance methods 
-    def save(*args)
-        cache.save(*args) if cache?
-        terminus.save(*args)
+    def save(instance, *args)
+        instance.version ||= Time.now.utc
+        dest = cache? ? cache : terminus
+        return if dest.fresh?(instance.name, instance.version)
+        cache.save(instance, *args) if cache?
+        terminus.save(instance, *args)
     end
 
     private
diff --git a/lib/puppet/indirector/terminus.rb b/lib/puppet/indirector/terminus.rb
index 3e0ea447c..5aeb4c6d7 100644
--- a/lib/puppet/indirector/terminus.rb
+++ b/lib/puppet/indirector/terminus.rb
@@ -95,25 +95,50 @@ class Puppet::Indirector::Terminus
         end
     end
 
+    # Is this instance fresh?  Meaning, is the version we have equivalent or better
+    # than the version being asked about
+    def fresh?(key, vers)
+        raise Puppet::DevError.new("Cannot check update status when no 'version' method is defined") unless respond_to?(:version)
+
+        if existing_version = version(key)
+            existing_version >= vers
+        else
+            false
+        end
+    end
+
+    def indirection
+        self.class.indirection
+    end
+
     def initialize
         if self.class.abstract_terminus?
             raise Puppet::DevError, "Cannot create instances of abstract terminus types"
         end
     end
     
-    def terminus_type
-        self.class.terminus_type
+    def model
+        self.class.model
     end
     
     def name
         self.class.name
     end
     
-    def model
-        self.class.model
+    def terminus_type
+        self.class.terminus_type
     end
 
-    def indirection
-        self.class.indirection
+    # Provide a default method for retrieving an instance's version.
+    # By default, just find the resource and get its version.  Individual
+    # terminus types can override this method to provide custom definitions of
+    # 'versions'.
+    def version(name)
+        raise Puppet::DevError.new("Cannot retrieve an instance's version without a :find method") unless respond_to?(:find)
+        if instance = find(name)
+            instance.version
+        else
+            nil
+        end
     end
 end