Review comments.

Signed-off-by: Steve Simpson <[email protected]>

Author: stevesg

integration/alertmanager_test.go

@@ -499,7 +499,7 @@ func TestAlertmanagerSharding(t *testing.T) {
 				require.NoError(t, err)
 			}
 
-			// Endpoint: GET /alerts
+			// Endpoint: GET /v1/alerts
 			{
 				// Reads will query at least two replicas and merge the results.
 				// Therefore, the alerts we posted should always be visible.

pkg/alertmanager/distributor.go

@@ -313,7 +313,7 @@ func respondFromMultipleHTTPGRPCResponses(w http.ResponseWriter, logger log.Logg
 	}
 
 	// It is assumed by using this function, the caller knows that the responses it receives
-	// have already need checked for success or failure, and that the headers will always
+	// have already been checked for success or failure, and that the headers will always
 	// match due to the nature of the request. If this is not the case, a different merge
 	// function should be implemented to cope with the differing responses.
 	response := &httpgrpc.HTTPResponse{

pkg/alertmanager/merger/merger.go

@@ -11,5 +11,8 @@ type Merger interface {
 type Noop struct{}
 
 func (Noop) MergeResponses(in [][]byte) ([]byte, error) {
+	if len(in) == 0 {
+		return nil, nil
+	}
 	return in[0], nil
 }

pkg/alertmanager/merger/v1_alerts.go

@@ -45,12 +45,7 @@ func (V1Alerts) MergeResponses(in [][]byte) ([]byte, error) {
 		Data:   merged,
 	}
 
-	result, err := json.Marshal(body)
-	if err != nil {
-		return nil, err
-	}
-
-	return result, nil
+	return json.Marshal(body)
 }
 
 func mergeV1Alerts(in []*v1.Alert) ([]*v1.Alert, error) {