Gracefully handle errors in parallel cases

lib/vagrant/batch_action.rb

@@ -53,15 +53,61 @@ module Vagrant
       @actions.each do |machine, action, options|
         @logger.info("Starting action: #{machine} #{action} #{options}")
 
-        thread = Thread.new { machine.send(:action, action, options) }
+        # Create the new thread to run our action. This is basically just
+        # calling the action but also contains some error handling in it
+        # as well.
+        thread = Thread.new do
+          Thread.current[:error] = nil
+
+          begin
+            machine.send(:action, action, options)
+          rescue Exception => e
+            # If we're not parallelizing, then raise the error
+            raise if !par
+
+            # Store the exception that will be processed later
+            Thread.current[:error] = e
+          end
+        end
+
+        # Set some attributes on the thread for later
+        thread[:machine] = machine
+
         thread.join if !par
         threads << thread
       end
 
-      # Join the threads, which will return immediately if parallelization
-      # if disabled, because we already joined on them. Otherwise, this
-      # will wait for completion of all threads.
-      threads.map(&:join)
+      errors = []
+
+      threads.each do |thread|
+        # Wait for the thread to complete
+        thread.join
+
+        # If the thread had an error, then store the error to show later
+        if thread[:error]
+          e = thread[:error]
+          # If the error isn't a Vagrant error, then store the backtrace
+          # as well.
+          if !thread[:error].is_a?(Errors::VagrantError)
+            e       = thread[:error]
+            message = e.message
+            message += "\n"
+            message += "\n#{e.backtrace.join("\n")}"
+
+            errors << I18n.t("vagrant.general.batch_unexpected_error",
+                             :machine => thread[:machine].name,
+                             :message => message)
+          else
+            errors << I18n.t("vagrant.general.batch_vagrant_error",
+                             :machine => thread[:machine].name,
+                             :message => thread[:error].message)
+          end
+        end
+      end
+
+      if !errors.empty?
+        raise Errors::BatchMultiError, :message => errors.join("\n\n")
+      end
     end
   end
 end

lib/vagrant/errors.rb

@@ -91,6 +91,10 @@ module Vagrant
       error_key(:base_vm_not_found)
     end
 
+    class BatchMultiError < VagrantError
+      error_key(:batch_multi_error)
+    end
+
     class BoxAlreadyExists < VagrantError
       error_key(:already_exists, "vagrant.actions.box.unpackage")
     end

plugins/providers/virtualbox/plugin.rb

@@ -9,7 +9,7 @@ module VagrantPlugins
       VirtualBox-based virtual machines.
       EOF
 
-      provider(:virtualbox) do
+      provider(:virtualbox, parallel: true) do
         require File.expand_path("../provider", __FILE__)
         Provider
       end

templates/locales/en.yml

@@ -1,6 +1,16 @@
 en:
   vagrant:
     general:
+      batch_unexpected_error: |-
+        An unexpected error ocurred when executing the action on the
+        '%{machine}' machine. Please report this as a bug:
+
+        %{message}
+      batch_vagrant_error: |-
+        An error occurred while executing the action on the '%{machine}'
+        machine. Please handle this error then try again:
+
+        %{message}
       config_upgrade_messages: |-
         There were warnings and/or errors while loading your Vagrantfile.
         Your Vagrantfile was written for an earlier version of Vagrant,
@@ -57,6 +67,11 @@ en:
         Active provider: %{active_provider}
         Requested provider: %{requested_provider}
       base_vm_not_found: The base VM with the name '%{name}' was not found.
+      batch_multi_error: |-
+        An error occurred while executing multiple actions in parallel.
+        Any errors that occurred are shown below.
+
+        %{message}
       box_metadata_file_not_found: |-
         The "metadata.json" file for the box '%{name}' was not found.
         Boxes require this file in order for Vagrant to determine the