handle responses in a seperate go routine to avoid deadlock

Signed-off-by: huabing zhao <[email protected]>

pkg/server/delta/v3/server.go

@@ -3,6 +3,7 @@ package delta
 import (
 	"context"
 	"errors"
+	"log"
 	"strconv"
 	"sync/atomic"
 
@@ -37,13 +38,6 @@ type Callbacks interface {
 
 var deltaErrorResponse = &cache.RawDeltaResponse{}
 
-// WithOrderedADS enables the internal flag to order responses strictly.
-func WithOrderedADS() config.XDSOption {
-	return func(o *config.Opts) {
-		o.Ordered = true
-	}
-}
-
 type server struct {
 	cache     cache.ConfigWatcher
 	callbacks Callbacks
@@ -116,30 +110,44 @@ func (s *server) processDelta(str stream.DeltaStream, reqCh <-chan *discovery.De
 		}
 	}
 
-	for {
-		select {
-		case <-s.ctx.Done():
-			return nil
-		case resp, more := <-watches.deltaMuxedResponses:
-			if !more {
-				break
-			}
+	done := make(chan struct{}, 1)
+	go func() {
+		for {
+			select {
+			case <-done:
+				return
+			case resp, more := <-watches.deltaMuxedResponses:
+				if !more {
+					break
+				}
 
-			typ := resp.GetDeltaRequest().GetTypeUrl()
-			if resp == deltaErrorResponse {
-				return status.Errorf(codes.Unavailable, typ+" watch failed")
-			}
+				typ := resp.GetDeltaRequest().GetTypeUrl()
+				if resp == deltaErrorResponse {
+					log.Printf("%s watch failed\n", typ)
+					break
+				}
 
-			nonce, err := send(resp)
-			if err != nil {
-				return err
-			}
+				nonce, err := send(resp)
+				if err != nil {
+					log.Printf("failed to send response %+v\n", err)
+					break
+				}
 
-			watch := watches.deltaWatches[typ]
-			watch.nonce = nonce
+				watches.mu.Lock()
+				watch := watches.deltaWatches[typ]
+				watch.nonce = nonce
+				watch.state.SetResourceVersions(resp.GetNextVersionMap())
+				watches.deltaWatches[typ] = watch
+				watches.mu.Unlock()
+			}
+		}
+	}()
 
-			watch.state.SetResourceVersions(resp.GetNextVersionMap())
-			watches.deltaWatches[typ] = watch
+	for {
+		select {
+		case <-s.ctx.Done():
+			done <- struct{}{}
+			return nil
 		case req, more := <-reqCh:
 			// input stream ended or errored out
 			if !more {
@@ -163,22 +171,19 @@ func (s *server) processDelta(str stream.DeltaStream, reqCh <-chan *discovery.De
 				req.Node = node
 			}
 
-			ordered := false
 			// type URL is required for ADS but is implicit for any other xDS stream
 			if defaultTypeURL == resource.AnyType {
 				if req.TypeUrl == "" {
 					return status.Errorf(codes.InvalidArgument, "type URL is required for ADS")
 				}
-				if s.opts.Ordered {
-					ordered = true
-				}
 			} else if req.TypeUrl == "" {
 				req.TypeUrl = defaultTypeURL
 			}
 
 			typeURL := req.GetTypeUrl()
 
 			// cancel existing watch to (re-)request a newer version
+			watches.mu.Lock()
 			watch, ok := watches.deltaWatches[typeURL]
 			if !ok {
 				// Initialize the state of the stream.
@@ -195,25 +200,10 @@ func (s *server) processDelta(str stream.DeltaStream, reqCh <-chan *discovery.De
 			s.subscribe(req.GetResourceNamesSubscribe(), &watch.state)
 			s.unsubscribe(req.GetResourceNamesUnsubscribe(), &watch.state)
 
-			if ordered {
-				// Use the shared channel to keep the order of responses.
-				watch.UseSharedResponseChan(watches.deltaMuxedResponses)
-			} else {
-				watch.MakeResponseChan()
-			}
+			watch.responses = watches.deltaMuxedResponses
 			watch.cancel = s.cache.CreateDeltaWatch(req, watch.state, watch.responses)
 			watches.deltaWatches[typeURL] = watch
-
-			// just handle normal non-ordered responses here
-			// all ordered responses are sent to the muxedResponses channel directly
-			if !watch.useSharedChan {
-				go func() {
-					resp, more := <-watch.responses
-					if more {
-						watches.deltaMuxedResponses <- resp
-					}
-				}()
-			}
+			watches.mu.Unlock()
 		}
 	}
 }

pkg/server/delta/v3/watches.go

@@ -1,6 +1,8 @@
 package delta
 
 import (
+	"sync"
+
 	"github.com/envoyproxy/go-control-plane/pkg/cache/types"
 	"github.com/envoyproxy/go-control-plane/pkg/cache/v3"
 	"github.com/envoyproxy/go-control-plane/pkg/server/stream/v3"
@@ -12,6 +14,8 @@ type watches struct {
 
 	// Opaque resources share a muxed channel
 	deltaMuxedResponses chan cache.DeltaResponse
+
+	mu sync.RWMutex
 }
 
 // newWatches creates and initializes watches.
@@ -28,36 +32,21 @@ func (w *watches) Cancel() {
 	for _, watch := range w.deltaWatches {
 		watch.Cancel()
 	}
+	close(w.deltaMuxedResponses)
 }
 
 // watch contains the necessary modifiables for receiving resource responses
 type watch struct {
-	responses     chan cache.DeltaResponse
-	useSharedChan bool // is this watch using a shared channel
-	cancel        func()
-	nonce         string
+	responses chan cache.DeltaResponse
+	cancel    func()
+	nonce     string
 
 	state stream.StreamState
 }
 
-func (w *watch) MakeResponseChan() {
-	w.responses = make(chan cache.DeltaResponse, 1)
-	w.useSharedChan = false
-}
-
-func (w *watch) UseSharedResponseChan(sharedChan chan cache.DeltaResponse) {
-	w.responses = sharedChan
-	w.useSharedChan = true
-}
-
 // Cancel calls terminate and cancel
 func (w *watch) Cancel() {
 	if w.cancel != nil {
 		w.cancel()
 	}
-	if w.responses != nil && !w.useSharedChan {
-		// w.responses should never be used by a producer once cancel() has been closed, so we can safely close it here
-		// This is needed to release resources taken by goroutines watching this channel
-		close(w.responses)
-	}
 }

pkg/server/v3/delta_test.go

@@ -15,7 +15,6 @@ import (
 	"github.com/envoyproxy/go-control-plane/pkg/cache/types"
 	"github.com/envoyproxy/go-control-plane/pkg/cache/v3"
 	rsrc "github.com/envoyproxy/go-control-plane/pkg/resource/v3"
-	"github.com/envoyproxy/go-control-plane/pkg/server/delta/v3"
 	"github.com/envoyproxy/go-control-plane/pkg/server/stream/v3"
 	"github.com/envoyproxy/go-control-plane/pkg/server/v3"
 	"github.com/envoyproxy/go-control-plane/pkg/test/resource/v3"
@@ -346,9 +345,7 @@ func TestDeltaAggregatedHandlers(t *testing.T) {
 		resp.recv <- r
 	}
 
-	// We create the server with the optional ordered ADS flag so we guarantee resource
-	// ordering over the stream.
-	s := server.NewServer(context.Background(), config, server.CallbackFuncs{}, delta.WithOrderedADS())
+	s := server.NewServer(context.Background(), config, server.CallbackFuncs{})
 	go func() {
 		err := s.DeltaAggregatedResources(resp)
 		assert.NoError(t, err)