lib/gitmodel.rb in gitmodel-0.0.4 vs lib/gitmodel.rb in gitmodel-0.0.5

@@ -1,14 +1,17 @@
+# coding: UTF-8
+
 require 'rubygems'
 require 'bundler/setup'
 
 require 'active_model'
 require 'active_support/all' # TODO we don't really want all here, clean this up
 require 'grit'
-require 'yajl'
 require 'lockfile'
+require 'memcache'
 require 'pp'
+require 'yajl'
 
 $:.unshift(File.dirname(__FILE__))
 require 'gitmodel/errors'
 require 'gitmodel/index'
 require 'gitmodel/persistable'
@@ -30,10 +33,13 @@
   self.logger.level = ::Logger::WARN
 
   mattr_accessor :git_user_name
   mattr_accessor :git_user_email
 
+  mattr_accessor :memcache_servers
+  mattr_accessor :memcache_namespace
+
   def self.repo
     @@repo = Grit::Repo.new(GitModel.db_root)
   end
 
   # Create the database defined in db_root. Raises an exception if it exists.
@@ -54,30 +60,66 @@
     logger.info "Deleting database #{db_root}!!"
     FileUtils.rm_rf db_root
     create_db!
   end
 
-  def self.last_commit(branch = nil)
-    branch ||= default_branch
-    # PERFORMANCE Cache this somewhere and update it on commit?
-    # (Need separate instance per branch)
-
-    return nil unless repo.commits(branch).any?
-
-    # We should be able to use just repo.commits(branch).first here but
-    # this is a workaround for this bug: 
-    # http://github.com/mojombo/grit/issues/issue/38
-    GitModel.repo.commits("#{branch}^..#{branch}").first || GitModel.repo.commits(branch).first
+  def self.last_commit(branch)
+    cache(branch, 'last-commit') do
+      unless repo.commits(branch).any?
+        nil
+      else
+        # We should be able to use just repo.commits(branch).first here but
+        # this is a workaround for this bug: 
+        # http://github.com/mojombo/grit/issues/issue/38
+        GitModel.repo.commits("#{branch}^..#{branch}").first || GitModel.repo.commits(branch).first
+      end
+    end
   end
 
-  def self.current_tree(branch = nil)
+  def self.current_tree(branch)
     c = last_commit(branch)
     c ? c.tree : nil
   end
 
-  def self.index!
-    dirs = (GitModel.current_tree).trees
+  def self.index!(branch)
+    dirs = (GitModel.current_tree(branch)).trees
     dirs.each do |dir|
-      dir.name.classify.constantize.index!
+      dir.name.classify.constantize.index!(branch)
     end
+  end
+
+  # If we're using memcached (i.e. the memcache_servers setting is not nil) and
+  # the key exists in memcached, it's value will be returned and the block will
+  # not be run.  If key does not exist in memcached, block will be executed,
+  # it's value stored in memcached under key, and value will be returned.
+  #
+  # There's no need to sweep the cache because the SHA of the latest Git commit
+  # is appended to the key, so any database change invalidates all cached
+  # objects.
+  def self.cache(branch, key, &block)
+    key = "#{key}-#{head_sha(branch)}"
+    value = nil
+    if memcache_servers
+      @@memcache ||= MemCache.new memcache_servers, :namespace => "#{File.basename(db_root)}-#{memcache_namespace}"
+      value = @@memcache.get(key)
+      if value.nil?
+        logger.info("✗ memcache MISS for key #{key}")
+        value = yield
+        @@memcache.set(key, value)
+      else
+        logger.info("✔ memcache HIT for key #{key}")
+      end
+    else
+      logger.debug("No memcache servers defined, not checking cache for key #{key}")
+      value = yield
+    end
+    value
+  end
+
+  private
+
+  # A more efficient way to get the SHA of the HEAD of the given branch
+  def self.head_sha(branch_name)
+    ref = File.join(repo.git.git_dir, "refs/heads/#{branch_name}")
+    File.exist?(ref) ? File.read(ref).chomp : nil
   end
 end