Clone arguments before calling workers to avoid mutation [#265]

Changes.md

@@ -3,6 +3,7 @@ HEAD
 
 - Handle networking errors causing the scheduler thread to die [#309]
 - Rework exception handling to log all Processor and actor death (#325, subelsky)
+- Clone arguments when calling worker so modifications are discarded. (hakanensari)
 
 2.1.0
 -----------

lib/sidekiq/processor.rb

@@ -37,7 +37,7 @@ module Sidekiq
 
       stats(worker, msg, queue) do
         Sidekiq.server_middleware.invoke(worker, msg, queue) do
-          worker.perform(*msg['args'])
+          worker.perform(*cloned(msg['args']))
         end
       end
       @boss.processor_done!(current_actor)
@@ -57,6 +57,9 @@ module Sidekiq
 
     private
 
+    # Singleton classes are not clonable.
+    SINGLETON_CLASSES = [ NilClass, TrueClass, FalseClass, Numeric, Symbol ].freeze
+
     def stats(worker, msg, queue)
       redis do |conn|
         conn.multi do
@@ -88,7 +91,15 @@ module Sidekiq
           end
         end
       end
+    end
 
+    # Clone the arguments passed to the worker so that if
+    # the message fails, what is pushed back onto Redis hasn't
+    # been mutated by the worker.
+    def cloned(ary)
+      ary.map do |val|
+        SINGLETON_CLASSES.include?(val.class) ? val : val.clone
+      end
     end
 
     def hostname

test/test_processor.rb

@@ -18,6 +18,7 @@ class TestProcessor < MiniTest::Unit::TestCase
       include Sidekiq::Worker
       def perform(args)
         raise TEST_EXCEPTION if args == 'boom'
+        args.pop if args.is_a? Array
         $invokes += 1
       end
     end
@@ -53,5 +54,14 @@ class TestProcessor < MiniTest::Unit::TestCase
 
       assert re_raise, "does not re-raise exceptions after handling"
     end
+
+    it 'does not modify original arguments' do
+      msg = { 'class' => MockWorker.to_s, 'args' => [['myarg']] }
+      msgstr = Sidekiq.dump_json(msg)
+      processor = ::Sidekiq::Processor.new(@boss)
+      @boss.expect(:processor_done!, nil, [processor])
+      processor.process(msgstr, 'default')
+      assert_equal [['myarg']], msg['args']
+    end
   end
 end