diff options
| -rw-r--r-- | lib/chef/node/attribute.rb | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/lib/chef/node/attribute.rb b/lib/chef/node/attribute.rb index c780650aac..03e199781f 100644 --- a/lib/chef/node/attribute.rb +++ b/lib/chef/node/attribute.rb @@ -175,11 +175,17 @@ class Chef # return the automatic level attribute component attr_reader :automatic - # this is used to track the top level key as we descend through method chaining into - # a precedence level (e.g. node.default['foo']['bar']['baz']= results in 'foo' here) + # This is used to track the top level key as we descend through method chaining into + # a precedence level (e.g. node.default['foo']['bar']['baz']= results in 'foo' here). We + # need this so that when we hit the end of a method chain which results in a mutator method + # that we can invalidate the whole top-level deep merge cache for the top-level key. It is + # the responsibility of the accessor on the Chef::Node object to reset this to nil, and then + # the first VividMash#[] call can ||= and set this to the first key we encounter. attr_accessor :top_level_breadcrumb - # cache of deep merged values by top-level key + # Cache of deep merged values by top-level key. This is a simple hash which has keys that are the + # top-level keys of the node object, and we save the computed deep-merge for that key here. There is + # no cache of subtrees. attr_accessor :deep_merge_cache def initialize(normal, default, override, automatic) @@ -239,6 +245,10 @@ class Chef @set_unless_present = setting end + # Invalidate a key in the deep_merge_cache. If called with nil, or no arg, this will invalidate + # the entire deep_merge cache. In the case of the user doing node.default['foo']['bar']['baz']= + # that eventually results in a call to reset_cache('foo') here. A node.default=hash_thing call + # must invalidate the entire cache and re-deep-merge the entire node object. def reset_cache(path = nil) if path.nil? @deep_merge_cache = {} @@ -404,7 +414,11 @@ class Chef end # - # Accessing merged attributes + # Accessing merged attributes. + # + # Note that merged_attributes('foo', 'bar', 'baz') can be called to compute only the + # deep merge of node['foo']['bar']['baz'], but in practice we currently always compute + # all of node['foo'] even if the user only requires node['foo']['bar']['baz']. # def merged_attributes(*path) @@ -421,8 +435,10 @@ class Chef def [](key) if deep_merge_cache.has_key?(key) + # return the cache of the deep merged values by top-level key deep_merge_cache[key] else + # save all the work of computing node[key] deep_merge_cache[key] = merged_attributes(key) end end |