Merge pull request #247 from jrafanie/cache_invalidation_is_harder

Only return the cached value if it exists.

lib/gems/pending/util/extensions/miq-module.rb

@@ -27,14 +27,15 @@ def cache_with_timeout(method, timeout = nil, &block)
 
         old_timeout = cache[:timeout]
         cache.clear if force_reload || (old_timeout && Time.now.utc > old_timeout)
-        break cache[:value] unless cache.empty?
+        break cache[:value] if cache.key?(:value)
 
         new_timeout = timeout || 300 # 5 minutes
         new_timeout = new_timeout.call if new_timeout.kind_of?(Proc)
         new_timeout = Time.now.utc + new_timeout
+        new_value   = block.call
 
         cache[:timeout] = new_timeout
-        cache[:value]   = block.call
+        cache[:value]   = new_value
       end
     end
 

spec/util/extensions/miq-module_spec.rb

@@ -41,6 +41,33 @@
       expect(test_module.default).to eq(value)
     end
 
+    it 'clears the cache even if the block raises an exception' do
+      test_class.define_singleton_method(:call_count)  { @call_count ||= 0 }
+      test_class.define_singleton_method(:call_count=) { |val| @call_count = val }
+      test_class.cache_with_timeout(:flapping_method) do
+        begin
+          if test_class.call_count.even?
+            test_class.call_count
+          else
+            raise "OOPS"
+          end
+        ensure
+          test_class.call_count += 1
+        end
+      end
+
+      expect(test_class.flapping_method(true)).to eq(0) # initializes cache to 0
+      expect(test_class.flapping_method).to eq(0)       # returns from cache
+
+      test_class.flapping_method(true) rescue nil       # blows up, clears cache for next request
+      expect(test_class.flapping_method).to eq(2)       # sets new value since cache is cleared
+      expect(test_class.flapping_method).to eq(2)       # returns from cache
+
+      test_class.flapping_method(true) rescue nil       # blows up, clears cache for next request
+      expect(test_class.flapping_method).to eq(4)       # sets new value since cache is cleared
+      expect(test_class.flapping_method).to eq(4)       # returns from cache
+    end
+
     it 'will not return the cached value when passed force_reload = true' do
       value = test_class.default(true)
       expect(test_class.default(true)).not_to eq(value)