From 48aef0c50e07b791196caa4ac40cef2c935ef288 Mon Sep 17 00:00:00 2001
From: Mitsuhiro Tanda <mitsuhiro.tanda@gmail.com>
Date: Tue, 16 Oct 2018 11:39:10 +0900
Subject: [PATCH] fix concurrent map writes

---
 pkg/tsdb/cloudwatch/cloudwatch.go | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/pkg/tsdb/cloudwatch/cloudwatch.go b/pkg/tsdb/cloudwatch/cloudwatch.go
index 61bbc04394a..437457df52a 100644
--- a/pkg/tsdb/cloudwatch/cloudwatch.go
+++ b/pkg/tsdb/cloudwatch/cloudwatch.go
@@ -86,9 +86,10 @@ func (e *CloudWatchExecutor) Query(ctx context.Context, dsInfo *models.DataSourc
 }
 
 func (e *CloudWatchExecutor) executeTimeSeriesQuery(ctx context.Context, queryContext *tsdb.TsdbQuery) (*tsdb.Response, error) {
-	result := &tsdb.Response{
+	results := &tsdb.Response{
 		Results: make(map[string]*tsdb.QueryResult),
 	}
+	resultChan := make(chan *tsdb.QueryResult, len(queryContext.Queries))
 
 	eg, ectx := errgroup.WithContext(ctx)
 
@@ -102,10 +103,10 @@ func (e *CloudWatchExecutor) executeTimeSeriesQuery(ctx context.Context, queryCo
 		RefId := queryContext.Queries[i].RefId
 		query, err := parseQuery(queryContext.Queries[i].Model)
 		if err != nil {
-			result.Results[RefId] = &tsdb.QueryResult{
+			results.Results[RefId] = &tsdb.QueryResult{
 				Error: err,
 			}
-			return result, nil
+			return results, nil
 		}
 		query.RefId = RefId
 
@@ -118,10 +119,10 @@ func (e *CloudWatchExecutor) executeTimeSeriesQuery(ctx context.Context, queryCo
 		}
 
 		if query.Id == "" && query.Expression != "" {
-			result.Results[query.RefId] = &tsdb.QueryResult{
+			results.Results[query.RefId] = &tsdb.QueryResult{
 				Error: fmt.Errorf("Invalid query: id should be set if using expression"),
 			}
-			return result, nil
+			return results, nil
 		}
 
 		eg.Go(func() error {
@@ -130,12 +131,13 @@ func (e *CloudWatchExecutor) executeTimeSeriesQuery(ctx context.Context, queryCo
 				return err
 			}
 			if err != nil {
-				result.Results[query.RefId] = &tsdb.QueryResult{
+				resultChan <- &tsdb.QueryResult{
+					RefId: query.RefId,
 					Error: err,
 				}
 				return nil
 			}
-			result.Results[queryRes.RefId] = queryRes
+			resultChan <- queryRes
 			return nil
 		})
 	}
@@ -149,10 +151,10 @@ func (e *CloudWatchExecutor) executeTimeSeriesQuery(ctx context.Context, queryCo
 					return err
 				}
 				for _, queryRes := range queryResponses {
-					result.Results[queryRes.RefId] = queryRes
 					if err != nil {
-						result.Results[queryRes.RefId].Error = err
+						queryRes.Error = err
 					}
+					resultChan <- queryRes
 				}
 				return nil
 			})
@@ -162,8 +164,12 @@ func (e *CloudWatchExecutor) executeTimeSeriesQuery(ctx context.Context, queryCo
 	if err := eg.Wait(); err != nil {
 		return nil, err
 	}
+	close(resultChan)
+	for result := range resultChan {
+		results.Results[result.RefId] = result
+	}
 
-	return result, nil
+	return results, nil
 }
 
 func (e *CloudWatchExecutor) executeQuery(ctx context.Context, query *CloudWatchQuery, queryContext *tsdb.TsdbQuery) (*tsdb.QueryResult, error) {