Add content-length as part of event notification structure (#6341)

Fixes #6321

cmd/handler-utils.go

@@ -189,6 +189,15 @@ func extractReqParams(r *http.Request) map[string]string {
 	}
 }
 
+// Extract response elements to be sent with event notifiation.
+func extractRespElements(w http.ResponseWriter) map[string]string {
+
+	return map[string]string{
+		"content-length": w.Header().Get("Content-Length"),
+		// Add more fields here.
+	}
+}
+
 // Trims away `aws-chunked` from the content-encoding header if present.
 // Streaming signature clients can have custom content-encoding such as
 // `aws-chunked,gzip` here we need to only save `gzip`.

cmd/notification.go

@@ -453,6 +453,7 @@ type eventArgs struct {
 	BucketName   string
 	Object       ObjectInfo
 	ReqParams    map[string]string
+	RespElements map[string]string
 	Host         string
 	Port         string
 	UserAgent    string
@@ -474,6 +475,13 @@ func (args eventArgs) ToEvent() event.Event {
 	eventTime := UTCNow()
 	uniqueID := fmt.Sprintf("%X", eventTime.UnixNano())
 
+	respElements := map[string]string{
+		"x-amz-request-id":        uniqueID,
+		"x-minio-origin-endpoint": getOriginEndpoint(), // Minio specific custom elements.
+	}
+	if args.RespElements["content-length"] != "" {
+		respElements["content-length"] = args.RespElements["content-length"]
+	}
 	newEvent := event.Event{
 		EventVersion:      "2.0",
 		EventSource:       "minio:s3",
@@ -482,10 +490,7 @@ func (args eventArgs) ToEvent() event.Event {
 		EventName:         args.EventName,
 		UserIdentity:      event.Identity{creds.AccessKey},
 		RequestParameters: args.ReqParams,
-		ResponseElements: map[string]string{
-			"x-amz-request-id":        uniqueID,
-			"x-minio-origin-endpoint": getOriginEndpoint(), // Minio specific custom elements.
-		},
+		ResponseElements:  respElements,
 		S3: event.Metadata{
 			SchemaVersion:   "1.0",
 			ConfigurationID: "Config",

cmd/object-handlers.go

@@ -409,6 +409,7 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
 		BucketName:   bucket,
 		Object:       objInfo,
 		ReqParams:    extractReqParams(r),
+		RespElements: extractRespElements(w),
 		UserAgent:    r.UserAgent(),
 		Host:         host,
 		Port:         port,
@@ -513,6 +514,7 @@ func (api objectAPIHandlers) HeadObjectHandler(w http.ResponseWriter, r *http.Re
 		BucketName:   bucket,
 		Object:       objInfo,
 		ReqParams:    extractReqParams(r),
+		RespElements: extractRespElements(w),
 		UserAgent:    r.UserAgent(),
 		Host:         host,
 		Port:         port,