add priority option in case some tool has inconsistent issue

config.go

@@ -5,6 +5,11 @@ import (
 	"time"
 )
 
+type UpstreamPriorityGroup struct {
+	Match    string `yaml:"match"`
+	Priority int    `yaml:"priority"`
+}
+
 type UpstreamMatch struct {
 	Match   string `yaml:"match"`
 	Replace string `yaml:"replace"`
@@ -14,6 +19,7 @@ type Upstream struct {
 	Server          string                  `yaml:"server"`
 	Match           UpstreamMatch           `yaml:"match"`
 	AllowedRedirect *string                 `yaml:"allowed-redirect"`
+	PriorityGroups  []UpstreamPriorityGroup `yaml:"priority-groups"`
 }
 
 func (upstream Upstream) GetPath(orig string) (string, bool, error) {

config.yaml

@@ -19,6 +19,9 @@ upstream:
   match:
     match: /ubuntu/(.*)
     replace: /$1
+  # priority-groups:
+  # - match: /dists/.*
+  #   priority: 10
 - server: https://releases.ubuntu.com/
   match:
     match: /ubuntu-releases/(.*)
@@ -51,10 +54,6 @@ upstream:
   match:
     match: /alpine/(.*)
     replace: /$1
-- server: https://deb.debian.org/debian
-  match:
-    match: /debian/(.*)
-    replace: /$1
 - server: https://repo.almalinux.org
   match:
     match: /almalinux/(.*)
@@ -71,6 +70,9 @@ upstream:
   match:
     match: /(debian|debian-security)/(.*)
     replace: /$1/$2
+  # priority-groups:
+  # - match: /dists/.*
+  #   priority: 10
 - server: https://static.rust-lang.org
   match:
     match: /rust-static/(.*)

server.go

@@ -80,12 +80,6 @@ OUTER:
 		offset += written
 	}
 	time.Sleep(time.Millisecond)
-	slog.With(
-		"start", offset,
-		"end", memoryObject.Buffer.Len(),
-		"n", memoryObject.Buffer.Len()-offset,
-	).Debug("remain bytes")
-
 	_, err := w.Write(memoryObject.Buffer.Bytes()[offset:])
 	return err
 }
@@ -312,8 +306,10 @@ func (server *Server) streamOnline(w http.ResponseWriter, r *http.Request, mtime
 		for chunk := range chunks {
 			if chunk.error != nil {
 				err = chunk.error
+				if !errors.Is(err, io.EOF) && !errors.Is(err, io.ErrUnexpectedEOF) {
 					slog.With("error", err).Warn("failed to read from upstream")
 				}
+			}
 			if chunk.buffer == nil {
 				break
 			}
@@ -423,9 +419,6 @@ func (server *Server) fastesUpstream(r *http.Request, lastModified time.Time) (r
 
 	resultIdx = -1
 
-	wg := &sync.WaitGroup{}
-	wg.Add(len(server.Upstreams))
-
 	defer close(updateCh)
 	defer close(notModifiedCh)
 	defer func() {
@@ -436,16 +429,55 @@ func (server *Server) fastesUpstream(r *http.Request, lastModified time.Time) (r
 			cancel()
 		}
 	}()
-	for idx := range server.Upstreams {
+
+	groups := make(map[int][]int)
+	for upstreamIdx, upstream := range server.Upstreams {
+		if _, matched, err := upstream.GetPath(r.URL.Path); err != nil {
+			return -1, nil, nil, err
+		} else if !matched {
+			continue
+		}
+
+		priority := 0
+		for _, priorityGroup := range upstream.PriorityGroups {
+			if matched, err := regexp.MatchString(priorityGroup.Match, r.URL.Path); err != nil {
+				return -1, nil, nil, err
+			} else if matched {
+				priority = priorityGroup.Priority
+				break
+			}
+		}
+		groups[priority] = append(groups[priority], upstreamIdx)
+	}
+
+	priorities := make([]int, 0, len(groups))
+	for priority := range groups {
+		priorities = append(priorities, priority)
+	}
+	slices.Sort(priorities)
+	slices.Reverse(priorities)
+
+	for _, priority := range priorities {
+		upstreams := groups[priority]
+
+		wg := &sync.WaitGroup{}
+		wg.Add(len(upstreams))
+
+		logger := slog.With()
+		if priority != 0 {
+			logger = logger.With("priority", priority)
+		}
+
+		for _, idx := range upstreams {
 			idx := idx
 			ctx, cancel := context.WithCancel(context.Background())
 			cancelFuncs[idx] = cancel
 
-		logger := slog.With("upstreamIdx", idx)
+			logger := logger.With("upstreamIdx", idx)
 
 			go func() {
 				defer wg.Done()
-			response, ch, err := server.tryUpstream(ctx, idx, r, lastModified)
+				response, ch, err := server.tryUpstream(ctx, idx, priority, r, lastModified)
 				if err == context.Canceled { // others returned
 					logger.Debug("context canceled")
 					return
@@ -481,6 +513,13 @@ func (server *Server) fastesUpstream(r *http.Request, lastModified time.Time) (r
 				updateOnce.Do(func() {
 					resultResponse, resultCh, resultErr = response, ch, err
 					updateCh <- idx
+
+					for cancelIdx, cancel := range cancelFuncs {
+						if cancelIdx == resultIdx || cancel == nil {
+							continue
+						}
+						cancel()
+					}
 				})
 
 				logger.Debug("voted update")
@@ -492,21 +531,24 @@ func (server *Server) fastesUpstream(r *http.Request, lastModified time.Time) (r
 		select {
 		case idx := <-updateCh:
 			resultIdx = idx
-		slog.With("upstreamIdx", resultIdx).Debug("upstream selected")
+			logger.With("upstreamIdx", resultIdx).Debug("upstream selected")
+			return
 		default:
 			select {
 			case idx := <-notModifiedCh:
 				resultIdx = idx
-			slog.With("upstreamIdx", resultIdx).Debug("all upstream not modified")
+				logger.With("upstreamIdx", resultIdx).Debug("all upstream not modified")
-		default:
-			slog.Debug("no valid upstream found")
-		}
-	}
-
 				return
+			default:
+				logger.Debug("no valid upstream found")
+			}
+		}
 	}
 
-func (server *Server) tryUpstream(ctx context.Context, upstreamIdx int, r *http.Request, lastModified time.Time) (response *http.Response, chunks chan Chunk, err error) {
+	return -1, nil, nil, nil
+}
+
+func (server *Server) tryUpstream(ctx context.Context, upstreamIdx, priority int, r *http.Request, lastModified time.Time) (response *http.Response, chunks chan Chunk, err error) {
 	upstream := server.Upstreams[upstreamIdx]
 
 	newpath, matched, err := upstream.GetPath(r.URL.Path)
@@ -517,6 +559,9 @@ func (server *Server) tryUpstream(ctx context.Context, upstreamIdx int, r *http.
 		return nil, nil, nil
 	}
 	logger := slog.With("upstreamIdx", upstreamIdx, "server", upstream.Server, "path", newpath)
+	if priority != 0 {
+		logger = logger.With("priority", priority)
+	}
 
 	logger.With(
 		"matched", matched,