[#60] Use periodic white space XML writer in Complete Multipart Upload

This mechanism is used by Amazon S3 to keep client's
connection alive while object is being constructed from
the upload parts.

Signed-off-by: Alex Vanin <a.vanin@yadro.com>

api/handler/api.go

@@ -34,6 +34,7 @@ type (
 		CopiesNumber               uint32
 		ResolveZoneList            []string
 		IsResolveListAllow         bool // True if ResolveZoneList contains allowed zones
+		CompleteMultipartKeepalive time.Duration
 	}
 
 	PlacementPolicy interface {

api/handler/multipart_upload.go

@@ -400,9 +400,15 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 		Parts: reqBody.Parts,
 	}
 
+	// Next operations might take some time, so we want to keep client's
+	// connection alive. To do so, gateway sends periodic white spaces
+	// back to the client the same way as Amazon S3 service does.
+	stopPeriodicResponseWriter := periodicXMLWriter(w, h.cfg.CompleteMultipartKeepalive)
+
 	uploadData, extendedObjInfo, err := h.obj.CompleteMultipartUpload(r.Context(), c)
 	if err != nil {
-		h.logAndSendError(w, "could not complete multipart upload", reqInfo, err, additional...)
+		logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
+		logAndSendError(w, "could not complete multipart upload", reqInfo, err, additional...)
 		return
 	}
 	objInfo := extendedObjInfo.ObjectInfo
@@ -418,7 +424,8 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 			NodeVersion: extendedObjInfo.NodeVersion,
 		}
 		if _, err = h.obj.PutObjectTagging(r.Context(), tagPrm); err != nil {
-			h.logAndSendError(w, "could not put tagging file of completed multipart upload", reqInfo, err, additional...)
+			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
+			logAndSendError(w, "could not put tagging file of completed multipart upload", reqInfo, err, additional...)
 			return
 		}
 	}
@@ -426,12 +433,14 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 	if len(uploadData.ACLHeaders) != 0 {
 		key, err := h.bearerTokenIssuerKey(r.Context())
 		if err != nil {
-			h.logAndSendError(w, "couldn't get gate key", reqInfo, err)
+			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
+			logAndSendError(w, "couldn't get gate key", reqInfo, err)
 			return
 		}
 		acl, err := parseACLHeaders(r.Header, key)
 		if err != nil {
-			h.logAndSendError(w, "could not parse acl", reqInfo, err)
+			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
+			logAndSendError(w, "could not parse acl", reqInfo, err)
 			return
 		}
 
@@ -441,11 +450,13 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 		}
 		astObject, err := aclToAst(acl, resInfo)
 		if err != nil {
-			h.logAndSendError(w, "could not translate acl of completed multipart upload to ast", reqInfo, err, additional...)
+			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
+			logAndSendError(w, "could not translate acl of completed multipart upload to ast", reqInfo, err, additional...)
 			return
 		}
 		if _, err = h.updateBucketACL(r, astObject, bktInfo, sessionTokenSetEACL); err != nil {
-			h.logAndSendError(w, "could not update bucket acl while completing multipart upload", reqInfo, err, additional...)
+			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
+			logAndSendError(w, "could not update bucket acl while completing multipart upload", reqInfo, err, additional...)
 			return
 		}
 	}
@@ -460,24 +471,26 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 		h.log.Error("couldn't send notification: %w", zap.Error(err))
 	}
 
-	bktSettings, err := h.obj.GetBucketSettings(r.Context(), bktInfo)
-	if err != nil {
-		h.logAndSendError(w, "could not get bucket settings", reqInfo, err)
-	}
-
 	response := CompleteMultipartUploadResponse{
 		Bucket: objInfo.Bucket,
 		ETag:   objInfo.HashSum,
 		Key:    objInfo.Name,
 	}
 
-	if bktSettings.VersioningEnabled() {
+	// Here we previously set api.AmzVersionID header for versioned bucket.
-		w.Header().Set(api.AmzVersionID, objInfo.VersionID())
+	// It is not possible after #60, because we introduced periodic white
-	}
+	// space XML writer to keep connection with the client.
 
+	headerIsWritten := stopPeriodicResponseWriter()
+	if headerIsWritten {
+		if err = api.EncodeToResponseNoHeader(w, response); err != nil {
+			h.logAndSendErrorNoHeader(w, "something went wrong", reqInfo, err)
+		}
+	} else {
 		if err = api.EncodeToResponse(w, response); err != nil {
 			h.logAndSendError(w, "something went wrong", reqInfo, err)
 		}
+	}
 }
 
 func (h *handler) ListMultipartUploadsHandler(w http.ResponseWriter, r *http.Request) {
@@ -732,3 +745,12 @@ func periodicXMLWriter(w io.Writer, dur time.Duration) (stop func() bool) {
 
 	return stop
 }
+
+// periodicWriterErrorSender returns handler function to send error. If header is
+// alreay written by periodic XML writer, do not send HTTP and XML headers.
+func (h *handler) periodicWriterErrorSender(headerWritten bool) func(http.ResponseWriter, string, *api.ReqInfo, error, ...zap.Field) {
+	if headerWritten {
+		return h.logAndSendErrorNoHeader
+	}
+	return h.logAndSendError
+}

cmd/s3-gw/app.go

@@ -654,6 +654,8 @@ func (a *App) initHandler() {
 		cfg.ResolveZoneList = a.cfg.GetStringSlice(cfgResolveBucketDeny)
 	}
 
+	cfg.CompleteMultipartKeepalive = a.cfg.GetDuration(cfgKludgeCompleteMultipartUploadKeepalive)
+
 	var err error
 	a.api, err = handler.New(a.log, a.obj, a.nc, cfg)
 	if err != nil {

cmd/s3-gw/app_settings.go

@@ -115,6 +115,7 @@ const ( // Settings.
 
 	// Kludge.
 	cfgKludgeUseDefaultXMLNSForCompleteMultipartUpload = "kludge.use_default_xmlns_for_complete_multipart"
+	cfgKludgeCompleteMultipartUploadKeepalive          = "kludge.complete_multipart_keepalive"
 
 	// Command line args.
 	cmdHelp      = "help"
@@ -258,6 +259,7 @@ func newSettings() *viper.Viper {
 
 	// kludge
 	v.SetDefault(cfgKludgeUseDefaultXMLNSForCompleteMultipartUpload, false)
+	v.SetDefault(cfgKludgeCompleteMultipartUploadKeepalive, 10*time.Second)
 
 	// Bind flags
 	if err := bindFlags(v, flags); err != nil {

config/config.env

@@ -130,3 +130,5 @@ S3_GW_RESOLVE_BUCKET_ALLOW=container
 
 # Enable using default xml namespace `http://s3.amazonaws.com/doc/2006-03-01/` when parse`CompleteMultipartUpload` xml body.
 S3_GW_KLUDGE_USE_DEFAULT_XMLNS_FOR_COMPLETE_MULTIPART=false
+# Set timeout between whitespace transmissions during CompleteMultipartUpload processing.
+S3_GW_KLUDGE_COMPLETE_MULTIPART_KEEPALIVE=10s

config/config.yaml

@@ -153,3 +153,5 @@ resolve_bucket:
 kludge:
   # Enable using default xml namespace `http://s3.amazonaws.com/doc/2006-03-01/` when parse`CompleteMultipartUpload` xml body.
   use_default_xmlns_for_complete_multipart: false
+  # Set timeout between whitespace transmissions during CompleteMultipartUpload processing.
+  complete_multipart_keepalive: 10s

docs/configuration.md

@@ -504,8 +504,10 @@ Workarounds for non-standard use cases.
 ```yaml
 kludge:
   use_default_xmlns_for_complete_multipart: false
+  complete_multipart_keepalive: 10s
 ```
 
 | Parameter                                  | Type       | SIGHUP reload | Default value | Description                                                                                                                 |
-|--------------------------------------------|--------|---------------|---------------|-----------------------------------------------------------------------------------------------------------------------------|
+|--------------------------------------------|------------|---------------|---------------|-----------------------------------------------------------------------------------------------------------------------------|
 | `use_default_xmlns_for_complete_multipart` | `bool`     | yes           | false         | Enable using default xml namespace `http://s3.amazonaws.com/doc/2006-03-01/` when parse `CompleteMultipartUpload` xml body. |
+| `complete_multipart_keepalive`             | `duration` | no            | 10s           | Set timeout between whitespace transmissions during CompleteMultipartUpload processing.                                     |