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xds/clusterresolver: implement gRFC A61 changes for LOGICAL_DNS clusters #8733

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bcdff79
remove hardcoded 'pickfirst' from logical_dns
Pranjali-2501 Dec 1, 2025
7183bc4
resolving comments
Pranjali-2501 Dec 3, 2025
d434565
resolving comments
Pranjali-2501 Dec 15, 2025
1aa62ea
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Pranjali-2501 Dec 17, 2025
1c62f2e
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Pranjali-2501 Dec 30, 2025
fc30718
convert test into e2e test
Pranjali-2501 Jan 5, 2026
529067c
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Pranjali-2501 Jan 6, 2026
3b917f4
resolving comments
Pranjali-2501 Jan 6, 2026
1ac89ad
fix test
Pranjali-2501 Jan 6, 2026
88e547e
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Pranjali-2501 Jan 7, 2026
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Pranjali-2501 Jan 28, 2026
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2 changes: 1 addition & 1 deletion internal/xds/balancer/cdsbalancer/e2e_test/aggregate_cluster_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1000,7 +1000,7 @@ func (s) TestAggregateCluster_BadEDS_BadDNS(t *testing.T) {
if err == nil {
t.Fatal("EmptyCall() succeeded when expected to fail")
}
if status.Code(err) == codes.Unavailable && strings.Contains(err.Error(), "produced zero addresses") {
if status.Code(err) == codes.Unavailable && strings.Contains(err.Error(), "no targets to pick from") {
break
}
}
Expand Down
135 changes: 135 additions & 0 deletions internal/xds/balancer/cdsbalancer/e2e_test/dns_impl_test.go
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@@ -0,0 +1,135 @@
/*
* Copyright 2026 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package e2e_test

import (
"context"
"fmt"
"testing"

"github.com/google/uuid"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials/insecure"
"google.golang.org/grpc/internal"
"google.golang.org/grpc/internal/stubserver"
"google.golang.org/grpc/internal/testutils/xds/e2e"
"google.golang.org/grpc/peer"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/resolver/manual"

v3clusterpb "github.com/envoyproxy/go-control-plane/envoy/config/cluster/v3"
v3listenerpb "github.com/envoyproxy/go-control-plane/envoy/config/listener/v3"
v3routepb "github.com/envoyproxy/go-control-plane/envoy/config/route/v3"
testpb "google.golang.org/grpc/interop/grpc_testing"

_ "google.golang.org/grpc/internal/xds/balancer/clusterresolver"
)

// TestLogicalDNS_MultipleEndpoints tests the cluster_resolver LB policy
// using a LOGICAL_DNS discovery mechanism.
//
// The test verifies that multiple addresses returned by the DNS resolver are
// grouped into a single endpoint (as per gRFC A61). Because the round_robin
// LB policy sees only one endpoint, it should not rotate traffic between the
// addresses. Instead, the single endpoint is picked, and connects to the
// first address.
func (s) TestLogicalDNS_MultipleEndpoints(t *testing.T) {
// Spin up a management server to receive xDS resources from.
managementServer := e2e.StartManagementServer(t, e2e.ManagementServerOptions{})

// Create bootstrap configuration pointing to the above management server.
nodeID := uuid.New().String()
bootstrapContents := e2e.DefaultBootstrapContents(t, nodeID, managementServer.Address)
resolverBuilder, err := internal.NewXDSResolverWithConfigForTesting.(func([]byte) (resolver.Builder, error))(bootstrapContents)
if err != nil {
t.Fatalf("Failed to create xDS resolver for testing: %v", err)
}

// Start backend servers which provide an implementation of the TestService.
server1 := stubserver.StartTestService(t, nil)
defer server1.Stop()
server2 := stubserver.StartTestService(t, nil)
defer server2.Stop()

// Register a manual resolver with the "dns" scheme to override DNS resolution.
// This global override is safe because connection to the xDS management
// server uses the passthrough scheme instead and therefore overriding
// the DNS resolver does not affect it in any way.
const dnsScheme = "dns"
dnsR := manual.NewBuilderWithScheme(dnsScheme)
originalDNS := resolver.Get("dns")
resolver.Register(dnsR)
t.Cleanup(func() { resolver.Register(originalDNS) })

// For LOGICAL_DNS, this updates the SINGLE endpoint to have 2 IPs.
dnsR.InitialState(resolver.State{
Endpoints: []resolver.Endpoint{{
Addresses: []resolver.Address{
{Addr: server1.Address},
{Addr: server2.Address},
}}},
})

const (
serviceName = "test-xds-service"
clusterName = "cluster-test-xds-service"
endpointsName = "endpoints-test-xds-service"
rdsName = "route-test-xds-service"
)

resources := e2e.UpdateOptions{
NodeID: nodeID,
Listeners: []*v3listenerpb.Listener{e2e.DefaultClientListener(serviceName, rdsName)},
Routes: []*v3routepb.RouteConfiguration{e2e.DefaultRouteConfig(rdsName, serviceName, clusterName)},
Clusters: []*v3clusterpb.Cluster{e2e.ClusterResourceWithOptions(e2e.ClusterOptions{
ClusterName: clusterName,
ServiceName: endpointsName,
Type: e2e.ClusterTypeLogicalDNS,
DNSHostName: "dns",
DNSPort: uint32(8080),
Policy: e2e.LoadBalancingPolicyRoundRobin,
})},
Endpoints: nil,
}

ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
defer cancel()

if err := managementServer.Update(ctx, resources); err != nil {
t.Fatalf("Failed to update management server: %v", err)
}

// Create a ClientConn and make a successful RPC.
cc, err := grpc.NewClient(fmt.Sprintf("xds:///"+serviceName), grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithResolvers(resolverBuilder))
if err != nil {
t.Fatalf("Failed to create new client for local test server: %v", err)
}
defer cc.Close()

// Ensure the RPC is routed to the first backend.
testClient := testpb.NewTestServiceClient(cc)
for i := 0; i < 10; i++ {
var peer peer.Peer
if _, err := testClient.EmptyCall(ctx, &testpb.Empty{}, grpc.Peer(&peer)); err != nil {
t.Fatalf("RPC failed: %v", err)
}

if got, want := peer.Addr.String(), server1.Address; got != want {
t.Errorf("peer.Addr = %q, want = %q", got, want)
}
}
}
9 changes: 2 additions & 7 deletions internal/xds/balancer/clusterimpl/tests/balancer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -989,14 +989,9 @@ func (s) TestReResolutionAfterTransientFailure(t *testing.T) {
}

// Stopping the server listener will close the transport on the client,
// which will lead to the channel eventually moving to IDLE.
// which will lead to the channel eventually moving to TRANSIENT_FAILURE.
lis.Stop()
testutils.AwaitState(ctx, t, conn, connectivity.Idle)

// An RPC at this point is expected to fail with TRANSIENT_FAILURE.
if _, err = client.EmptyCall(ctx, &testpb.Empty{}); status.Code(err) != codes.Unavailable {
t.Fatalf("EmptyCall RPC succeeded when the channel is in TRANSIENT_FAILURE, got %v want %v", err, codes.Unavailable)
}
testutils.AwaitState(ctx, t, conn, connectivity.TransientFailure)

// Expect resolver's ResolveNow to be called due to TF state.
select {
Expand Down
44 changes: 27 additions & 17 deletions internal/xds/balancer/clusterresolver/configbuilder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ import (
"google.golang.org/grpc/internal/xds/balancer/outlierdetection"
"google.golang.org/grpc/internal/xds/balancer/priority"
"google.golang.org/grpc/internal/xds/balancer/wrrlocality"
"google.golang.org/grpc/internal/xds/clients"
"google.golang.org/grpc/internal/xds/xdsclient/xdsresource"
"google.golang.org/grpc/resolver"
)
Expand Down Expand Up @@ -108,7 +109,7 @@ func buildPriorityConfig(priorities []priorityConfig, xdsLBPolicy *internalservi
}
continue
case DiscoveryMechanismTypeLogicalDNS:
name, config, endpoints := buildClusterImplConfigForDNS(p.childNameGen, p.endpoints, p.mechanism)
name, config, endpoints := buildClusterImplConfigForDNS(p.childNameGen, p.endpoints, p.mechanism, xdsLBPolicy)
retConfig.Priorities = append(retConfig.Priorities, name)
retEndpoints = append(retEndpoints, endpoints...)
odCfg := makeClusterImplOutlierDetectionChild(config, p.mechanism.outlierDetection)
Expand Down Expand Up @@ -138,27 +139,36 @@ func makeClusterImplOutlierDetectionChild(ciCfg *clusterimpl.LBConfig, odCfg out
return &odCfgRet
}

func buildClusterImplConfigForDNS(g *nameGenerator, endpoints []resolver.Endpoint, mechanism DiscoveryMechanism) (string, *clusterimpl.LBConfig, []resolver.Endpoint) {
// Endpoint picking policy for DNS is hardcoded to pick_first.
const childPolicy = "pick_first"
retEndpoints := make([]resolver.Endpoint, len(endpoints))
func buildClusterImplConfigForDNS(g *nameGenerator, endpoints []resolver.Endpoint, mechanism DiscoveryMechanism, xdsLBPolicy *internalserviceconfig.BalancerConfig) (string, *clusterimpl.LBConfig, []resolver.Endpoint) {
pName := fmt.Sprintf("priority-%v", g.prefix)
for i, e := range endpoints {
// For Logical DNS clusters, the same hostname attribute is added
// to all endpoints. It is set to the name that is resolved for the
// Logical DNS cluster, including the port number.
retEndpoints[i] = xdsresource.SetHostname(hierarchy.SetInEndpoint(e, []string{pName}), mechanism.DNSHostname)
// Copy the nested address field as slice fields are shared by the
// iteration variable and the original slice.
retEndpoints[i].Addresses = append([]resolver.Address{}, e.Addresses...)
}
return pName, &clusterimpl.LBConfig{
lbconfig := &clusterimpl.LBConfig{
Cluster: mechanism.Cluster,
TelemetryLabels: mechanism.TelemetryLabels,
ChildPolicy: &internalserviceconfig.BalancerConfig{Name: childPolicy},
ChildPolicy: xdsLBPolicy,
MaxConcurrentRequests: mechanism.MaxConcurrentRequests,
LoadReportingServer: mechanism.LoadReportingServer,
}, retEndpoints
}
if len(endpoints) == 0 {
return pName, lbconfig, nil
}
var retEndpoint resolver.Endpoint
for _, e := range endpoints {
// LOGICAL_DNS requires all resolved addresses to be grouped into a
// single logical endpoint. We iterate over the input endpoints and
// aggregate their addresses into a new endpoint variable.
retEndpoint.Addresses = append(retEndpoint.Addresses, e.Addresses...)
}
// Even though localities are not a thing for the LOGICAL_DNS cluster and
// its endpoint(s), we add an empty locality attribute here to ensure that
// LB policies that rely on locality information (like weighted_target)
// continue to work.
localityStr := xdsinternal.LocalityString(clients.Locality{})
retEndpoint = xdsresource.SetHostname(hierarchy.SetInEndpoint(retEndpoint, []string{pName, localityStr}), mechanism.DNSHostname)
// Set the locality weight to 1. This is required because the child policy
// like weighted_target which relies on locality weights to distribute
// traffic. These policies may drop traffic if the weight is 0.
retEndpoint = wrrlocality.SetAddrInfo(retEndpoint, wrrlocality.AddrInfo{LocalityWeight: 1})
return pName, lbconfig, []resolver.Endpoint{retEndpoint}
}

// buildClusterImplConfigForEDS returns a list of cluster_impl configs, one for
Expand Down
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