Add text/event-stream for long running http connections (#7909)

When MinIO is behind a proxy, proxies end up killing
clients when no data is seen on the connection, adding
the right content-type ensures that proxies do not come
in the way.

cmd/admin-handlers.go

@@ -681,12 +681,12 @@ func (a adminAPIHandlers) HealHandler(w http.ResponseWriter, r *http.Request) {
 					// Start writing response to client
 					started = true
 					setCommonHeaders(w)
-					w.Header().Set(xhttp.ContentType, string(mimeJSON))
+					w.Header().Set(xhttp.ContentType, "text/event-stream")
 					// Set 200 OK status
 					w.WriteHeader(200)
 				}
 				// Send whitespace and keep connection open
-				w.Write([]byte("\n\r"))
+				w.Write([]byte(" "))
 				w.(http.Flusher).Flush()
 			case hr := <-respCh:
 				switch hr.apiErr {
@@ -1486,7 +1486,8 @@ func (a adminAPIHandlers) TraceHandler(w http.ResponseWriter, r *http.Request) {
 	// Avoid reusing tcp connection if read timeout is hit
 	// This is needed to make r.Context().Done() work as
 	// expected in case of read timeout
-	w.Header().Add(xhttp.Connection, "close")
+	w.Header().Set(xhttp.Connection, "close")
+	w.Header().Set(xhttp.ContentType, "text/event-stream")
 
 	doneCh := make(chan struct{})
 	defer close(doneCh)

cmd/bucket-notification-handlers.go

@@ -23,6 +23,7 @@ import (
 	"net/http"
 
 	"github.com/gorilla/mux"
+	xhttp "github.com/minio/minio/cmd/http"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/event"
 	"github.com/minio/minio/pkg/event/target"
@@ -246,6 +247,8 @@ func (api objectAPIHandlers) ListenBucketNotificationHandler(w http.ResponseWrit
 		return
 	}
 
+	w.Header().Set(xhttp.ContentType, "text/event-stream")
+
 	target, err := target.NewHTTPClientTarget(*host, w)
 	if err != nil {
 		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL, guessIsBrowserReq(r))

cmd/object-handlers.go

@@ -2280,6 +2280,7 @@ func (api objectAPIHandlers) CompleteMultipartUploadHandler(w http.ResponseWrite
 		w.Write(encodedErrorResponse)
 		w.(http.Flusher).Flush()
 	}
+	w.Header().Set(xhttp.ContentType, "text/event-stream")
 	w = &whiteSpaceWriter{ResponseWriter: w, Flusher: w.(http.Flusher)}
 	completeDoneCh := sendWhiteSpace(ctx, w)
 	objInfo, err := completeMultiPartUpload(ctx, bucket, object, uploadID, completeParts, opts)

cmd/storage-rest-server.go

@@ -540,6 +540,7 @@ func (s *storageRESTServer) VerifyFile(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	algo := BitrotAlgorithmFromString(algoStr)
+	w.Header().Set(xhttp.ContentType, "text/event-stream")
 	doneCh := sendWhiteSpaceVerifyFile(w)
 	err = s.storage.VerifyFile(volume, filePath, algo, hash, int64(shardSize))
 	<-doneCh