Merge pull request #174 from instacart/cachefix

Fixes `can't add a new key into hash during iteration` error

lib/makara/cache/memory_store.rb

@@ -4,6 +4,7 @@ class MemoryStore
 
       def initialize
         @data = {}
+        @mutex = Mutex.new
       end
 
       def read(key)
@@ -20,7 +21,9 @@ def write(key, value, options = {})
       protected
 
       def clean
-        @data.delete_if{|k,v| v[1] <= Time.now.to_i }
+        @mutex.synchronize do
+          @data.delete_if{|k,v| v[1] <= Time.now.to_i }
+        end
       end
 
     end

spec/cache_spec.rb

@@ -52,6 +52,28 @@
       expect(data).not_to have_key('test')
     end
 
+    it 'has thread-safety' do
+      store = Makara::Cache::MemoryStore.new
+      previous_value = Thread.abort_on_exception
+
+      begin
+        Thread.abort_on_exception = true
+
+        workers = 2.times.map do
+          Thread.new do
+            100.times do |n|
+              store.write(n, 'value', expires_in: 0.5)
+              sleep(0.01)
+            end
+          end
+        end
+
+        expect { workers.map(&:join) }.to_not raise_error
+      ensure
+        Thread.abort_on_exception = previous_value
+      end
+    end
+
   end