internal/backoff: add a helper to run a function with backoff (#6661)

internal/backoff/backoff.go

@@ -23,6 +23,8 @@
 package backoff
 
 import (
+	"context"
+	"errors"
 	"time"
 
 	grpcbackoff "google.golang.org/grpc/backoff"
@@ -71,3 +73,37 @@ func (bc Exponential) Backoff(retries int) time.Duration {
 	}
 	return time.Duration(backoff)
 }
+
+// ErrResetBackoff is the error to be returned by the function executed by RunF,
+// to instruct the latter to reset its backoff state.
+var ErrResetBackoff = errors.New("reset backoff state")
+
+// RunF provides a convenient way to run a function f repeatedly until the
+// context expires or f returns a non-nil error that is not ErrResetBackoff.
+// When f returns ErrResetBackoff, RunF continues to run f, but resets its
+// backoff state before doing so. backoff accepts an integer representing the
+// number of retries, and returns the amount of time to backoff.
+func RunF(ctx context.Context, f func() error, backoff func(int) time.Duration) {
+	attempt := 0
+	timer := time.NewTimer(0)
+	for ctx.Err() == nil {
+		select {
+		case <-timer.C:
+		case <-ctx.Done():
+			timer.Stop()
+			return
+		}
+
+		err := f()
+		if errors.Is(err, ErrResetBackoff) {
+			timer.Reset(0)
+			attempt = 0
+			continue
+		}
+		if err != nil {
+			return
+		}
+		timer.Reset(backoff(attempt))
+		attempt++
+	}
+}

orca/producer.go

@@ -24,6 +24,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/internal/backoff"
 	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/orca/internal"
 	"google.golang.org/grpc/status"
@@ -169,48 +170,29 @@ func (p *producer) updateRunLocked() {
 func (p *producer) run(ctx context.Context, done chan struct{}, interval time.Duration) {
 	defer close(done)
 
-	backoffAttempt := 0
-	backoffTimer := time.NewTimer(0)
-	for ctx.Err() == nil {
-		select {
-		case <-backoffTimer.C:
-		case <-ctx.Done():
-			return
-		}
-
+	runStream := func() error {
 		resetBackoff, err := p.runStream(ctx, interval)
-
-		if resetBackoff {
-			backoffTimer.Reset(0)
-			backoffAttempt = 0
-		} else {
-			backoffTimer.Reset(p.backoff(backoffAttempt))
-			backoffAttempt++
-		}
-
-		switch {
-		case err == nil:
-			// No error was encountered; restart the stream.
-		case ctx.Err() != nil:
-			// Producer was stopped; exit immediately and without logging an
-			// error.
-			return
-		case status.Code(err) == codes.Unimplemented:
+		if status.Code(err) == codes.Unimplemented {
 			// Unimplemented; do not retry.
 			logger.Error("Server doesn't support ORCA OOB load reporting protocol; not listening for load reports.")
-			return
-		case status.Code(err) == codes.Unavailable, status.Code(err) == codes.Canceled:
-			// TODO: these codes should ideally log an error, too, but for now
-			// we receive them when shutting down the ClientConn (Unavailable
-			// if the stream hasn't started yet, and Canceled if it happens
-			// mid-stream).  Once we can determine the state or ensure the
-			// producer is stopped before the stream ends, we can log an error
-			// when it's not a natural shutdown.
-		default:
-			// Log all other errors.
+			return err
+		}
+		// Retry for all other errors.
+		if code := status.Code(err); code != codes.Unavailable && code != codes.Canceled {
+			// TODO: Unavailable and Canceled should also ideally log an error,
+			// but for now we receive them when shutting down the ClientConn
+			// (Unavailable if the stream hasn't started yet, and Canceled if it
+			// happens mid-stream).  Once we can determine the state or ensure
+			// the producer is stopped before the stream ends, we can log an
+			// error when it's not a natural shutdown.
 			logger.Error("Received unexpected stream error:", err)
 		}
+		if resetBackoff {
+			return backoff.ErrResetBackoff
+		}
+		return nil
 	}
+	backoff.RunF(ctx, runStream, p.backoff)
 }
 
 // runStream runs a single stream on the subchannel and returns the resulting

xds/internal/xdsclient/transport/loadreport.go

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/golang/protobuf/ptypes"
+	"google.golang.org/grpc/internal/backoff"
 	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/internal/pretty"
 	"google.golang.org/grpc/xds/internal"
@@ -100,54 +101,36 @@ func (t *Transport) lrsRunner(ctx context.Context) {
 	node := proto.Clone(t.nodeProto).(*v3corepb.Node)
 	node.ClientFeatures = append(node.ClientFeatures, "envoy.lrs.supports_send_all_clusters")
 
-	backoffAttempt := 0
-	backoffTimer := time.NewTimer(0)
-	for ctx.Err() == nil {
-		select {
-		case <-backoffTimer.C:
-		case <-ctx.Done():
-			backoffTimer.Stop()
-			return
+	runLoadReportStream := func() error {
+		// streamCtx is created and canceled in case we terminate the stream
+		// early for any reason, to avoid gRPC-Go leaking the RPC's monitoring
+		// goroutine.
+		streamCtx, cancel := context.WithCancel(ctx)
+		defer cancel()
+		stream, err := v3lrsgrpc.NewLoadReportingServiceClient(t.cc).StreamLoadStats(streamCtx)
+		if err != nil {
+			t.logger.Warningf("Creating LRS stream to server %q failed: %v", t.serverURI, err)
+			return nil
+		}
+		t.logger.Infof("Created LRS stream to server %q", t.serverURI)
+
+		if err := t.sendFirstLoadStatsRequest(stream, node); err != nil {
+			t.logger.Warningf("Sending first LRS request failed: %v", err)
+			return nil
+		}
+
+		clusters, interval, err := t.recvFirstLoadStatsResponse(stream)
+		if err != nil {
+			t.logger.Warningf("Reading from LRS stream failed: %v", err)
+			return nil
 		}
 
 		// We reset backoff state when we successfully receive at least one
 		// message from the server.
-		resetBackoff := func() bool {
-			// streamCtx is created and canceled in case we terminate the stream
-			// early for any reason, to avoid gRPC-Go leaking the RPC's monitoring
-			// goroutine.
-			streamCtx, cancel := context.WithCancel(ctx)
-			defer cancel()
-			stream, err := v3lrsgrpc.NewLoadReportingServiceClient(t.cc).StreamLoadStats(streamCtx)
-			if err != nil {
-				t.logger.Warningf("Creating LRS stream to server %q failed: %v", t.serverURI, err)
-				return false
-			}
-			t.logger.Infof("Created LRS stream to server %q", t.serverURI)
-
-			if err := t.sendFirstLoadStatsRequest(stream, node); err != nil {
-				t.logger.Warningf("Sending first LRS request failed: %v", err)
-				return false
-			}
-
-			clusters, interval, err := t.recvFirstLoadStatsResponse(stream)
-			if err != nil {
-				t.logger.Warningf("Reading from LRS stream failed: %v", err)
-				return false
-			}
-
-			t.sendLoads(streamCtx, stream, clusters, interval)
-			return true
-		}()
-
-		if resetBackoff {
-			backoffTimer.Reset(0)
-			backoffAttempt = 0
-		} else {
-			backoffTimer.Reset(t.backoff(backoffAttempt))
-			backoffAttempt++
-		}
+		t.sendLoads(streamCtx, stream, clusters, interval)
+		return backoff.ErrResetBackoff
 	}
+	backoff.RunF(ctx, runLoadReportStream, t.backoff)
 }
 
 func (t *Transport) sendLoads(ctx context.Context, stream lrsStream, clusterNames []string, interval time.Duration) {

xds/internal/xdsclient/transport/transport.go

@@ -325,43 +325,29 @@ func (t *Transport) adsRunner(ctx context.Context) {
 
 	go t.send(ctx)
 
-	backoffAttempt := 0
-	backoffTimer := time.NewTimer(0)
-	for ctx.Err() == nil {
+	// We reset backoff state when we successfully receive at least one
+	// message from the server.
+	runStreamWithBackoff := func() error {
+		stream, err := t.newAggregatedDiscoveryServiceStream(ctx, t.cc)
+		if err != nil {
+			t.onErrorHandler(err)
+			t.logger.Warningf("Creating new ADS stream failed: %v", err)
+			return nil
+		}
+		t.logger.Infof("ADS stream created")
+
 		select {
-		case <-backoffTimer.C:
-		case <-ctx.Done():
-			backoffTimer.Stop()
-			return
+		case <-t.adsStreamCh:
+		default:
 		}
-
-		// We reset backoff state when we successfully receive at least one
-		// message from the server.
-		resetBackoff := func() bool {
-			stream, err := t.newAggregatedDiscoveryServiceStream(ctx, t.cc)
-			if err != nil {
-				t.onErrorHandler(err)
-				t.logger.Warningf("Creating new ADS stream failed: %v", err)
-				return false
-			}
-			t.logger.Infof("ADS stream created")
-
-			select {
-			case <-t.adsStreamCh:
-			default:
-			}
-			t.adsStreamCh <- stream
-			return t.recv(stream)
-		}()
-
-		if resetBackoff {
-			backoffTimer.Reset(0)
-			backoffAttempt = 0
-		} else {
-			backoffTimer.Reset(t.backoff(backoffAttempt))
-			backoffAttempt++
+		t.adsStreamCh <- stream
+		msgReceived := t.recv(stream)
+		if msgReceived {
+			return backoff.ErrResetBackoff
 		}
+		return nil
 	}
+	backoff.RunF(ctx, runStreamWithBackoff, t.backoff)
 }
 
 // send is a separate goroutine for sending resource requests on the ADS stream.