Add admin API to send console log messages (#7784)

Utilized by mc admin console command.

cmd/peer-rest-server.go

@@ -32,6 +32,7 @@ import (
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/event"
 	"github.com/minio/minio/pkg/lifecycle"
+	"github.com/minio/minio/pkg/madmin"
 	xnet "github.com/minio/minio/pkg/net"
 	"github.com/minio/minio/pkg/policy"
 	trace "github.com/minio/minio/pkg/trace"
@@ -903,6 +904,38 @@ func (s *peerRESTServer) BackgroundOpsStatusHandler(w http.ResponseWriter, r *ht
 	logger.LogIf(ctx, gob.NewEncoder(w).Encode(state))
 }
 
+// ConsoleLogHandler sends console logs of this node back to peer rest client
+func (s *peerRESTServer) ConsoleLogHandler(w http.ResponseWriter, r *http.Request) {
+	if !s.IsValid(w, r) {
+		s.writeErrorResponse(w, errors.New("Invalid request"))
+		return
+	}
+
+	w.Header().Set("Connection", "close")
+	w.WriteHeader(http.StatusOK)
+	w.(http.Flusher).Flush()
+
+	doneCh := make(chan struct{})
+	defer close(doneCh)
+
+	ch := make(chan interface{}, 2000)
+	globalConsoleSys.Subscribe(ch, doneCh, "", 0, nil)
+
+	enc := gob.NewEncoder(w)
+	for {
+		select {
+		case entry := <-ch:
+			log := entry.(madmin.LogInfo)
+			if err := enc.Encode(log); err != nil {
+				return
+			}
+			w.(http.Flusher).Flush()
+		case <-r.Context().Done():
+			return
+		}
+	}
+}
+
 func (s *peerRESTServer) writeErrorResponse(w http.ResponseWriter, err error) {
 	w.WriteHeader(http.StatusForbidden)
 	w.Write([]byte(err.Error()))
@@ -958,6 +991,7 @@ func registerPeerRESTHandlers(router *mux.Router) {
 
 	subrouter.Methods(http.MethodPost).Path(SlashSeparator + peerRESTMethodTrace).HandlerFunc(server.TraceHandler)
 	subrouter.Methods(http.MethodPost).Path(SlashSeparator + peerRESTMethodBackgroundHealStatus).HandlerFunc(server.BackgroundHealStatusHandler)
+	subrouter.Methods(http.MethodPost).Path(SlashSeparator + peerRESTMethodLog).HandlerFunc(server.ConsoleLogHandler)
 
 	router.NotFoundHandler = http.HandlerFunc(httpTraceAll(notFoundHandler))
 }