fix: avoid buffering of server sent events by proxies (#10164)

cmd/admin-handlers.go

@@ -695,7 +695,7 @@ func (a adminAPIHandlers) HealHandler(w http.ResponseWriter, r *http.Request) {
 					// Start writing response to client
 					started = true
 					setCommonHeaders(w)
-					w.Header().Set(xhttp.ContentType, "text/event-stream")
+					setEventStreamHeaders(w)
 					// Set 200 OK status
 					w.WriteHeader(200)
 				}
@@ -995,7 +995,7 @@ func (a adminAPIHandlers) TraceHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 
 	// Trace Publisher and peer-trace-client uses nonblocking send and hence does not wait for slow receivers.
 	// Use buffered channel to take care of burst sends or slow w.Write()
@@ -1064,7 +1064,8 @@ func (a adminAPIHandlers) ConsoleLogHandler(w http.ResponseWriter, r *http.Reque
 	// This is needed to make r.Context().Done() work as
 	// expected in case of read timeout
 	w.Header().Add("Connection", "close")
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+
+	setEventStreamHeaders(w)
 
 	logCh := make(chan interface{}, 4000)
 
@@ -1223,7 +1224,9 @@ func (a adminAPIHandlers) OBDInfoHandler(w http.ResponseWriter, r *http.Request)
 	}
 
 	setCommonHeaders(w)
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+
+	setEventStreamHeaders(w)
+
 	w.WriteHeader(http.StatusOK)
 
 	errResp := func(err error) {

cmd/api-headers.go

@@ -38,6 +38,13 @@ func mustGetRequestID(t time.Time) string {
 	return fmt.Sprintf("%X", t.UnixNano())
 }
 
+// setEventStreamHeaders to allow proxies to avoid buffering proxy responses
+func setEventStreamHeaders(w http.ResponseWriter) {
+	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	w.Header().Set(xhttp.CacheControl, "no-cache") // nginx to turn off buffering
+	w.Header().Set("X-Accel-Buffering", "no")      // nginx to turn off buffering
+}
+
 // Write http common headers
 func setCommonHeaders(w http.ResponseWriter) {
 	w.Header().Set(xhttp.ServerInfo, "MinIO/"+ReleaseTag)

cmd/listen-notification-handlers.go

@@ -22,7 +22,6 @@ import (
 	"time"
 
 	"github.com/gorilla/mux"
-	xhttp "github.com/minio/minio/cmd/http"
 	"github.com/minio/minio/cmd/logger"
 	policy "github.com/minio/minio/pkg/bucket/policy"
 	"github.com/minio/minio/pkg/event"
@@ -119,7 +118,7 @@ func (api objectAPIHandlers) ListenNotificationHandler(w http.ResponseWriter, r
 
 	rulesMap := event.NewRulesMap(eventNames, pattern, event.TargetID{ID: mustGetUUID()})
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 
 	// Listen Publisher and peer-listen-client uses nonblocking send and hence does not wait for slow receivers.
 	// Use buffered channel to take care of burst sends or slow w.Write()

cmd/object-handlers.go

@@ -2615,7 +2615,9 @@ func (api objectAPIHandlers) CompleteMultipartUploadHandler(w http.ResponseWrite
 		w.Write(encodedErrorResponse)
 		w.(http.Flusher).Flush()
 	}
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+
+	setEventStreamHeaders(w)
+
 	w = &whiteSpaceWriter{ResponseWriter: w, Flusher: w.(http.Flusher)}
 	completeDoneCh := sendWhiteSpace(w)
 	objInfo, err := completeMultiPartUpload(ctx, bucket, object, uploadID, completeParts, opts)

cmd/storage-rest-server.go

@@ -151,7 +151,8 @@ func (s *storageRESTServer) CrawlAndGetDataUsageHandler(w http.ResponseWriter, r
 		return
 	}
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
+
 	var cache dataUsageCache
 	err := cache.deserialize(r.Body)
 	if err != nil {
@@ -520,7 +521,7 @@ func (s *storageRESTServer) WalkSplunkHandler(w http.ResponseWriter, r *http.Req
 	dirPath := vars[storageRESTDirPath]
 	markerPath := vars[storageRESTMarkerPath]
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 	encoder := gob.NewEncoder(w)
 
 	fch, err := s.storage.WalkSplunk(volume, dirPath, markerPath, r.Context().Done())
@@ -548,7 +549,7 @@ func (s *storageRESTServer) WalkVersionsHandler(w http.ResponseWriter, r *http.R
 		return
 	}
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 	encoder := gob.NewEncoder(w)
 
 	fch, err := s.storage.WalkVersions(volume, dirPath, markerPath, recursive, r.Context().Done())
@@ -576,7 +577,7 @@ func (s *storageRESTServer) WalkHandler(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 	encoder := gob.NewEncoder(w)
 
 	fch, err := s.storage.Walk(volume, dirPath, markerPath, recursive, r.Context().Done())
@@ -659,7 +660,7 @@ func (s *storageRESTServer) DeleteVersionsHandler(w http.ResponseWriter, r *http
 
 	dErrsResp := &DeleteVersionsErrsResp{Errs: make([]error, totalVersions)}
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 	encoder := gob.NewEncoder(w)
 	done := keepHTTPResponseAlive(w)
 	errs := s.storage.DeleteVersions(volume, versions)
@@ -805,7 +806,7 @@ func (s *storageRESTServer) VerifyFileHandler(w http.ResponseWriter, r *http.Req
 		return
 	}
 
-	w.Header().Set(xhttp.ContentType, "text/event-stream")
+	setEventStreamHeaders(w)
 	encoder := gob.NewEncoder(w)
 	done := keepHTTPResponseAlive(w)
 	err = s.storage.VerifyFile(volume, filePath, fi)