add RetryAttempts to AccessLog in JSON format

middlewares/accesslog/logdata.go

@@ -68,6 +68,8 @@ const (
 	GzipRatio = "GzipRatio"
 	// Overhead is the map key used for the processing time overhead caused by Traefik.
 	Overhead = "Overhead"
+	// RetryAttempts is the map key used for the amount of attempts the request was retried.
+	RetryAttempts = "RetryAttempts"
 )
 
 // These are written out in the default case when no config is provided to specify keys of interest.
@@ -110,6 +112,7 @@ func init() {
 	allCoreKeys[GzipRatio] = struct{}{}
 	allCoreKeys[StartLocal] = struct{}{}
 	allCoreKeys[Overhead] = struct{}{}
+	allCoreKeys[RetryAttempts] = struct{}{}
 }
 
 // CoreLogData holds the fields computed from the request/response.