pickfirstleaf: Fix shuffling of addresses in resolver updates without endpoints

balancer/pickfirst/pickfirst.go

@@ -169,7 +169,7 @@ func (b *pickfirstBalancer) UpdateClientConnState(state balancer.ClientConnState
 		addrs = state.ResolverState.Addresses
 		if cfg.ShuffleAddressList {
 			addrs = append([]resolver.Address{}, addrs...)
-			rand.Shuffle(len(addrs), func(i, j int) { addrs[i], addrs[j] = addrs[j], addrs[i] })
+			internal.RandShuffle(len(addrs), func(i, j int) { addrs[i], addrs[j] = addrs[j], addrs[i] })
 		}
 	}
 

balancer/pickfirst/pickfirst_ext_test.go

@@ -20,6 +20,7 @@ package pickfirst_test
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"strings"
@@ -28,11 +29,14 @@ import (
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/backoff"
+	"google.golang.org/grpc/balancer"
+	pfbalancer "google.golang.org/grpc/balancer/pickfirst"
 	pfinternal "google.golang.org/grpc/balancer/pickfirst/internal"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/connectivity"
 	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/internal/balancer/stub"
 	"google.golang.org/grpc/internal/channelz"
 	"google.golang.org/grpc/internal/grpctest"
 	"google.golang.org/grpc/internal/stubserver"
@@ -463,6 +467,85 @@ func (s) TestPickFirst_ShuffleAddressList(t *testing.T) {
 	}
 }
 
+// Tests the PF LB policy with shuffling enabled. It explicitly unsets the
+// Endpoints field in the resolver update to test the shuffling of the
+// Addresses.
+func (s) TestPickFirst_ShuffleAddressListNoEndpoints(t *testing.T) {
+	// Install a shuffler that always reverses two entries.
+	origShuf := pfinternal.RandShuffle
+	defer func() { pfinternal.RandShuffle = origShuf }()
+	pfinternal.RandShuffle = func(n int, f func(int, int)) {
+		if n != 2 {
+			t.Errorf("Shuffle called with n=%v; want 2", n)
+			return
+		}
+		f(0, 1) // reverse the two addresses
+	}
+
+	pfBuilder := balancer.Get(pfbalancer.Name)
+	shffleConfig, err := pfBuilder.(balancer.ConfigParser).ParseConfig(json.RawMessage(`{ "shuffleAddressList": true }`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	noShffleConfig, err := pfBuilder.(balancer.ConfigParser).ParseConfig(json.RawMessage(`{ "shuffleAddressList": false }`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	activeCfg := noShffleConfig
+
+	bf := stub.BalancerFuncs{
+		Init: func(bd *stub.BalancerData) {
+			bd.ChildBalancer = pfBuilder.Build(bd.ClientConn, bd.BuildOptions)
+		},
+		Close: func(bd *stub.BalancerData) {
+			bd.ChildBalancer.Close()
+		},
+		UpdateClientConnState: func(bd *stub.BalancerData, ccs balancer.ClientConnState) error {
+			ccs.BalancerConfig = activeCfg
+			ccs.ResolverState.Endpoints = nil
+			return bd.ChildBalancer.UpdateClientConnState(ccs)
+		},
+	}
+
+	stub.Register(t.Name(), bf)
+	svcCfg := fmt.Sprintf(`{ "loadBalancingConfig": [{%q: {}}] }`, t.Name())
+	// Set up our backends.
+	cc, r, backends := setupPickFirst(t, 2, grpc.WithDefaultServiceConfig(svcCfg))
+	addrs := stubBackendsToResolverAddrs(backends)
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	// Push an update with both addresses and shuffling disabled.  We should
+	// connect to backend 0.
+	activeCfg = noShffleConfig
+	resolverState := resolver.State{Addresses: addrs}
+	r.UpdateState(resolverState)
+	if err := pickfirst.CheckRPCsToBackend(ctx, cc, addrs[0]); err != nil {
+		t.Fatal(err)
+	}
+
+	// Send a config with shuffling enabled.  This will reverse the addresses,
+	// but the channel should still be connected to backend 0.
+	activeCfg = shffleConfig
+	r.UpdateState(resolverState)
+	if err := pickfirst.CheckRPCsToBackend(ctx, cc, addrs[0]); err != nil {
+		t.Fatal(err)
+	}
+
+	// Send a resolver update with no addresses. This should push the channel
+	// into TransientFailure.
+	r.UpdateState(resolver.State{})
+	testutils.AwaitState(ctx, t, cc, connectivity.TransientFailure)
+
+	// Send the same config as last time with shuffling enabled.  Since we are
+	// not connected to backend 0, we should connect to backend 1.
+	r.UpdateState(resolverState)
+	if err := pickfirst.CheckRPCsToBackend(ctx, cc, addrs[1]); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // Test config parsing with the env var turned on and off for various scenarios.
 func (s) TestPickFirst_ParseConfig_Success(t *testing.T) {
 	// Install a shuffler that always reverses two entries.

balancer/pickfirst/pickfirstleaf/pickfirstleaf.go

@@ -283,7 +283,7 @@ func (b *pickfirstBalancer) UpdateClientConnState(state balancer.ClientConnState
 		newAddrs = state.ResolverState.Addresses
 		if cfg.ShuffleAddressList {
 			newAddrs = append([]resolver.Address{}, newAddrs...)
-			internal.RandShuffle(len(endpoints), func(i, j int) { endpoints[i], endpoints[j] = endpoints[j], endpoints[i] })
+			internal.RandShuffle(len(newAddrs), func(i, j int) { newAddrs[i], newAddrs[j] = newAddrs[j], newAddrs[i] })
 		}
 	}