Merge pull request #15 from tarent/error-500-on-empty

Error 500 on empty fetch job list

composition/composition_handler.go

@@ -32,6 +32,13 @@ func (agg *CompositionHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)
 
 	fetcher := agg.contentFetcherFactory(r)
 
+	if fetcher.Empty() {
+		w.WriteHeader(500)
+		w.Write([]byte("Internal server error"))
+		logging.Application(r.Header).Error("No fetchers available for composition, throwing error 500")
+		return
+	}
+
 	// fetch all contents
 	results := fetcher.WaitForResults()
 

composition/composition_handler_test.go

@@ -190,6 +190,24 @@ func Test_CompositionHandler_ErrorInFetching(t *testing.T) {
 	a.Equal(502, resp.Code)
 }
 
+func Test_CompositionHandler_ErrorEmptyFetchersList(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	a := assert.New(t)
+
+	contentFetcherFactory := func(r *http.Request) FetchResultSupplier {
+		return MockFetchResultSupplier{}
+	}
+	aggregator := NewCompositionHandler(ContentFetcherFactory(contentFetcherFactory))
+
+	resp := httptest.NewRecorder()
+	r, _ := http.NewRequest("GET", "http://example.com", nil)
+	aggregator.ServeHTTP(resp, r)
+
+	a.Equal("Internal server error", string(resp.Body.Bytes()))
+	a.Equal(500, resp.Code)
+}
+
 func Test_metadataForRequest(t *testing.T) {
 	a := assert.New(t)
 	r, _ := http.NewRequest("GET", "https://example.com/nothing?foo=bar", nil)
@@ -265,3 +283,8 @@ func (m MockFetchResultSupplier) WaitForResults() []*FetchResult {
 func (m MockFetchResultSupplier) MetaJSON() map[string]interface{} {
 	return nil
 }
+
+func (m MockFetchResultSupplier) Empty() bool {
+	return len([]*FetchResult(m)) == 0
+}
+

composition/content_fetcher.go

@@ -108,6 +108,12 @@ func (fetcher *ContentFetcher) AddFetchJob(d *FetchDefinition) {
 	}()
 }
 
+func (fetcher *ContentFetcher) Empty() bool {
+	fetcher.r.mutex.Lock()
+	defer fetcher.r.mutex.Unlock()
+	return len(fetcher.r.results) == 0
+}
+
 // isAlreadySheduled checks, if there is already a job for a FetchDefinition, or it is already fetched.
 // The method has to be called in a locked mutex block.
 func (fetcher *ContentFetcher) isAlreadySheduled(fetchDefinitionHash string) bool {

composition/content_fetcher_test.go

@@ -34,6 +34,21 @@ func Test_ContentFetcher_FetchingWithDependency(t *testing.T) {
 	meta := fetcher.MetaJSON()
 	a.Equal("bar", meta["foo"])
 	a.Equal("bla", meta["bli"])
+
+	a.False(fetcher.Empty())
+}
+
+func Test_ContentFetcher_Empty(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	a := assert.New(t)
+
+	loader := NewMockContentLoader(ctrl)
+
+	fetcher := NewContentFetcher(nil)
+	fetcher.Loader = loader
+
+	a.True(fetcher.Empty())
 }
 
 func getFetchDefinitionMock(ctrl *gomock.Controller, loaderMock *MockContentLoader, url string, requiredContent []*FetchDefinition, loaderBlocking time.Duration, metaJSON map[string]interface{}) *FetchDefinition {

composition/interfaces.go

@@ -34,6 +34,9 @@ type FetchResultSupplier interface {
 
 	// MetaJSON returns the composed meta JSON object
 	MetaJSON() map[string]interface{}
+
+	// True, if no fetch jobs were added
+	Empty() bool
 }
 
 type CacheStrategy interface {