Improve the thread safety of BoxCollection

lib/vagrant/box_collection.rb

@@ -1,4 +1,5 @@
 require "digest/sha1"
+require "thread"
 require "tmpdir"
 
 require "log4r"
@@ -43,6 +44,7 @@ module Vagrant
       options ||= {}
 
       @directory = directory
+      @lock      = Mutex.new
       @temp_root = options[:temp_dir_root]
       @logger    = Log4r::Logger.new("vagrant::box_collection")
     end
@@ -69,6 +71,7 @@ module Vagrant
     # @param [Boolean] force If true, any existing box with the same name
     #   and provider will be replaced.
     def add(path, name, provider=nil, force=false)
+      with_collection_lock do
         # A helper to check if a box exists. We store this in a variable
         # since we call it multiple times.
         check_box_exists = lambda do |box_provider|
@@ -163,6 +166,7 @@ module Vagrant
             end
           end
         end
+      end
 
       # Return the box
       find(name, provider)
@@ -177,6 +181,7 @@ module Vagrant
     def all
       results = []
 
+      with_collection_lock do
         @logger.debug("Finding all boxes in: #{@directory}")
         @directory.children(true).each do |child|
           # Ignore non-directories, since files are not interesting to
@@ -207,6 +212,7 @@ module Vagrant
             end
           end
         end
+      end
 
       results
     end
@@ -217,6 +223,7 @@ module Vagrant
     # @Param [String] provider Provider that the box implements.
     # @return [Box] The box found, or `nil` if not found.
     def find(name, provider)
+      with_collection_lock do
         # First look directly for the box we're asking for.
         box_directory = @directory.join(name, provider.to_s, "metadata.json")
         @logger.info("Searching for box: #{name} (#{provider}) in #{box_directory}")
@@ -242,6 +249,7 @@ module Vagrant
             raise Errors::BoxUpgradeRequired, :name => name
           end
         end
+      end
 
       # Didn't find it, return nil
       @logger.info("Box not found: #{name} (#{provider})")
@@ -255,6 +263,7 @@ module Vagrant
     #
     # @return [Boolean] `true` otherwise an exception is raised.
     def upgrade(name)
+      with_collection_lock do
         @logger.debug("Upgrade request for box: #{name}")
         box_dir = @directory.join(name)
 
@@ -271,6 +280,7 @@ module Vagrant
           FileUtils.mv(temp_dir.to_s, box_dir.join("virtualbox").to_s)
           @logger.info("Box '#{name}' upgraded from V1 to V2.")
         end
+      end
 
       # We did it! Or the v1 box didn't exist so it doesn't matter.
       return true
@@ -330,6 +340,24 @@ module Vagrant
       temp_dir
     end
 
+    # This locks the region given by the block with a lock on this
+    # collection.
+    def with_collection_lock
+      lock = @lock
+
+      begin
+        lock.synchronize {}
+      rescue ThreadError
+        # If we already hold the lock, just create a new lock so
+        # we definitely don't block and don't get an error.
+        lock = Mutex.new
+      end
+
+      lock.synchronize do
+        return yield
+      end
+    end
+
     # This is a helper that makes sure that our temporary directories
     # are cleaned up no matter what.
     #

lib/vagrant/environment.rb

@@ -331,7 +331,6 @@ module Vagrant
       # Determine the possible box formats for any boxes and find the box
       box_formats = provider_options[:box_format] || provider
       box = nil
-      box = find_box(config.vm.box, box_formats) if config.vm.box
 
       # Set this variable in order to keep track of if the box changes
       # too many times.
@@ -339,6 +338,8 @@ module Vagrant
       box_changed  = false
 
       load_box_and_overrides = lambda do
+        box = find_box(config.vm.box, box_formats) if config.vm.box
+
         # If a box was found, then we attempt to load the Vagrantfile for
         # that box. We don't require a box since we allow providers to download
         # boxes and so on.
@@ -378,7 +379,6 @@ module Vagrant
           @logger.info("Box changed to: #{config.vm.box}. Reloading configurations.")
           original_box = config.vm.box
           box_changed  = true
-          box          = find_box(config.vm.box, box_formats)
 
           # Recurse so that we reload all the configurations
           load_box_and_overrides.call