server: ensure that service-defaults meta is incorporated into the discovery chain response (#12511)

Also add a new "Default" field to the discovery chain response to clients

.changelog/12511.txt

@@ -0,0 +1,7 @@
+```release-note:feature
+server: ensure that service-defaults meta is incorporated into the discovery chain response
+```
+
+```release-note:feature
+server: discovery chains now include a response field named "Default" to indicate if they were not constructed from any service-resolver, service-splitter, or service-router config entries
+```

agent/consul/discovery_chain_endpoint_test.go

@@ -98,6 +98,7 @@ func TestDiscoveryChainEndpoint_Get(t *testing.T) {
 			Datacenter:  "dc1",
 			Protocol:    "tcp",
 			StartNode:   "resolver:web.default.default.dc1",
+			Default:     true,
 			Nodes: map[string]*structs.DiscoveryGraphNode{
 				"resolver:web.default.default.dc1": {
 					Type: structs.DiscoveryGraphNodeTypeResolver,
@@ -286,12 +287,7 @@ func TestDiscoveryChainEndpoint_Get_BlockOnNoChange(t *testing.T) {
 				args.QueryOptions.MinQueryIndex = minQueryIndex
 
 				var out structs.DiscoveryChainResponse
-				errCh := channelCallRPC(s1, "DiscoveryChain.Get", &args, &out, func() error {
+				errCh := channelCallRPC(s1, "DiscoveryChain.Get", &args, &out, nil)
-					if !out.Chain.IsDefault() {
-						return fmt.Errorf("expected default chain")
-					}
-					return nil
-				})
 				return &out.QueryMeta, errCh
 			},
 			func(i int) <-chan error {

agent/consul/discoverychain/compile.go

@@ -161,6 +161,12 @@ type compiler struct {
 	// This is an OUTPUT field.
 	protocol string
 
+	// serviceMeta is the Meta field from the service-defaults entry that
+	// shares a name with this discovery chain.
+	//
+	// This is an OUTPUT field.
+	serviceMeta map[string]string
+
 	// startNode is computed inside of assembleChain()
 	//
 	// This is an OUTPUT field.
@@ -327,14 +333,47 @@ func (c *compiler) compile() (*structs.CompiledDiscoveryChain, error) {
 		Namespace:         c.evaluateInNamespace,
 		Partition:         c.evaluateInPartition,
 		Datacenter:        c.evaluateInDatacenter,
+		Default:           c.determineIfDefaultChain(),
 		CustomizationHash: customizationHash,
 		Protocol:          c.protocol,
+		ServiceMeta:       c.serviceMeta,
 		StartNode:         c.startNode,
 		Nodes:             c.nodes,
 		Targets:           c.loadedTargets,
 	}, nil
 }
 
+//	determineIfDefaultChain returns true if the compiled chain represents no
+//	routing, no splitting, and only the default resolution.  We have to be
+//	careful here to avoid returning "yep this is default" when the only
+//	resolver action being applied is redirection to another resolver that is
+//	default, so we double check the resolver matches the requested resolver.
+//
+// NOTE: "default chain" mostly means that this is compatible with how things
+// worked (roughly) in consul 1.5 pre-discovery chain, not that there are zero
+// config entries in play (like service-defaults).
+func (c *compiler) determineIfDefaultChain() bool {
+	if c.startNode == "" || len(c.nodes) == 0 {
+		return true
+	}
+
+	node := c.nodes[c.startNode]
+	if node == nil {
+		panic("not possible: missing node named '" + c.startNode + "' in chain '" + c.serviceName + "'")
+	}
+
+	if node.Type != structs.DiscoveryGraphNodeTypeResolver {
+		return false
+	}
+	if !node.Resolver.Default {
+		return false
+	}
+
+	target := c.loadedTargets[node.Resolver.Target]
+
+	return target.Service == c.serviceName && target.Namespace == c.evaluateInNamespace && target.Partition == c.evaluateInPartition
+}
+
 func (c *compiler) detectCircularReferences() error {
 	var (
 		todo       stringStack
@@ -515,6 +554,11 @@ func (c *compiler) assembleChain() error {
 
 	sid := structs.NewServiceID(c.serviceName, c.GetEnterpriseMeta())
 
+	// Extract the service meta for the service named by this discovery chain.
+	if serviceDefault := c.entries.GetService(sid); serviceDefault != nil {
+		c.serviceMeta = serviceDefault.GetMeta()
+	}
+
 	// Check for short circuit path.
 	if len(c.resolvers) == 0 && c.entries.IsChainEmpty() {
 		// Materialize defaults and cache.

agent/consul/discoverychain/compile_test.go

@@ -12,14 +12,12 @@ import (
 )
 
 type compileTestCase struct {
-	entries *configentry.DiscoveryChainSet
+	entries        *configentry.DiscoveryChainSet
-	setup   func(req *CompileRequest)
+	setup          func(req *CompileRequest)
-	expect  *structs.CompiledDiscoveryChain
+	expect         *structs.CompiledDiscoveryChain
-	// expectIsDefault tests behavior of CompiledDiscoveryChain.IsDefault()
+	expectCustom   bool
-	expectIsDefault bool
+	expectErr      string
-	expectCustom    bool
+	expectGraphErr bool
-	expectErr       string
-	expectGraphErr  bool
 }
 
 func TestCompile(t *testing.T) {
@@ -56,6 +54,8 @@ func TestCompile(t *testing.T) {
 		"loadbalancer splitter and resolver":               testcase_LBSplitterAndResolver(),
 		"loadbalancer resolver":                            testcase_LBResolver(),
 		"service redirect to service with default resolver is not a default chain": testcase_RedirectToDefaultResolverIsNotDefaultChain(),
+		"service meta projection":               testcase_ServiceMetaProjection(),
+		"service meta projection with redirect": testcase_ServiceMetaProjectionWithRedirect(),
 
 		"all the bells and whistles": testcase_AllBellsAndWhistles(),
 		"multi dc canary":            testcase_MultiDatacenterCanary(),
@@ -141,7 +141,6 @@ func TestCompile(t *testing.T) {
 				}
 
 				require.Equal(t, tc.expect, res)
-				require.Equal(t, tc.expectIsDefault, res.IsDefault())
 			}
 		})
 	}
@@ -1429,6 +1428,7 @@ func testcase_DefaultResolver() compileTestCase {
 
 	expect := &structs.CompiledDiscoveryChain{
 		Protocol:  "tcp",
+		Default:   true,
 		StartNode: "resolver:main.default.default.dc1",
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:main.default.default.dc1": {
@@ -1446,7 +1446,7 @@ func testcase_DefaultResolver() compileTestCase {
 			"main.default.default.dc1": newTarget("main", "", "default", "default", "dc1", nil),
 		},
 	}
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: true}
+	return compileTestCase{entries: entries, expect: expect}
 }
 
 func testcase_DefaultResolver_WithProxyDefaults() compileTestCase {
@@ -1465,6 +1465,7 @@ func testcase_DefaultResolver_WithProxyDefaults() compileTestCase {
 
 	expect := &structs.CompiledDiscoveryChain{
 		Protocol:  "grpc",
+		Default:   true,
 		StartNode: "resolver:main.default.default.dc1",
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:main.default.default.dc1": {
@@ -1485,11 +1486,69 @@ func testcase_DefaultResolver_WithProxyDefaults() compileTestCase {
 			}),
 		},
 	}
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: true}
+	return compileTestCase{entries: entries, expect: expect}
 }
 
-func testcase_RedirectToDefaultResolverIsNotDefaultChain() compileTestCase {
+func testcase_ServiceMetaProjection() compileTestCase {
 	entries := newEntries()
+	entries.AddServices(
+		&structs.ServiceConfigEntry{
+			Kind: structs.ServiceDefaults,
+			Name: "main",
+			Meta: map[string]string{
+				"foo": "bar",
+				"abc": "123",
+			},
+		},
+	)
+	expect := &structs.CompiledDiscoveryChain{
+		Protocol: "tcp",
+		Default:  true,
+		ServiceMeta: map[string]string{
+			"foo": "bar",
+			"abc": "123",
+		},
+		StartNode: "resolver:main.default.default.dc1",
+		Nodes: map[string]*structs.DiscoveryGraphNode{
+			"resolver:main.default.default.dc1": {
+				Type: structs.DiscoveryGraphNodeTypeResolver,
+				Name: "main.default.default.dc1",
+				Resolver: &structs.DiscoveryResolver{
+					Default:        true,
+					ConnectTimeout: 5 * time.Second,
+					Target:         "main.default.default.dc1",
+				},
+			},
+		},
+		Targets: map[string]*structs.DiscoveryTarget{
+			"main.default.default.dc1": newTarget("main", "", "default", "default", "dc1", nil),
+		},
+	}
+
+	return compileTestCase{entries: entries, expect: expect}
+}
+
+func testcase_ServiceMetaProjectionWithRedirect() compileTestCase {
+	entries := newEntries()
+	entries.AddServices(
+		&structs.ServiceConfigEntry{
+			Kind: structs.ServiceDefaults,
+			Name: "main",
+			Meta: map[string]string{
+				"foo": "bar",
+				"abc": "123",
+			},
+		},
+		&structs.ServiceConfigEntry{
+			Kind: structs.ServiceDefaults,
+			Name: "other",
+			Meta: map[string]string{
+				"zim": "gir",
+				"abc": "456",
+				"xyz": "999",
+			},
+		},
+	)
 	entries.AddResolvers(
 		&structs.ServiceResolverConfigEntry{
 			Kind: structs.ServiceResolver,
@@ -1501,7 +1560,12 @@ func testcase_RedirectToDefaultResolverIsNotDefaultChain() compileTestCase {
 	)
 
 	expect := &structs.CompiledDiscoveryChain{
-		Protocol:  "tcp",
+		Protocol: "tcp",
+		ServiceMeta: map[string]string{
+			// Note this is main's meta, not other's.
+			"foo": "bar",
+			"abc": "123",
+		},
 		StartNode: "resolver:other.default.default.dc1",
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:other.default.default.dc1": {
@@ -1519,7 +1583,42 @@ func testcase_RedirectToDefaultResolverIsNotDefaultChain() compileTestCase {
 		},
 	}
 
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: false /*being explicit here because this is the whole point of this test*/}
+	return compileTestCase{entries: entries, expect: expect}
+}
+
+func testcase_RedirectToDefaultResolverIsNotDefaultChain() compileTestCase {
+	entries := newEntries()
+	entries.AddResolvers(
+		&structs.ServiceResolverConfigEntry{
+			Kind: structs.ServiceResolver,
+			Name: "main",
+			Redirect: &structs.ServiceResolverRedirect{
+				Service: "other",
+			},
+		},
+	)
+
+	expect := &structs.CompiledDiscoveryChain{
+		Protocol:  "tcp",
+		StartNode: "resolver:other.default.default.dc1",
+		Default:   false, /*being explicit here because this is the whole point of this test*/
+		Nodes: map[string]*structs.DiscoveryGraphNode{
+			"resolver:other.default.default.dc1": {
+				Type: structs.DiscoveryGraphNodeTypeResolver,
+				Name: "other.default.default.dc1",
+				Resolver: &structs.DiscoveryResolver{
+					Default:        true,
+					ConnectTimeout: 5 * time.Second,
+					Target:         "other.default.default.dc1",
+				},
+			},
+		},
+		Targets: map[string]*structs.DiscoveryTarget{
+			"other.default.default.dc1": newTarget("other", "", "default", "default", "dc1", nil),
+		},
+	}
+
+	return compileTestCase{entries: entries, expect: expect}
 }
 
 func testcase_Resolve_WithDefaultSubset() compileTestCase {
@@ -1570,6 +1669,7 @@ func testcase_DefaultResolver_ExternalSNI() compileTestCase {
 
 	expect := &structs.CompiledDiscoveryChain{
 		Protocol:  "tcp",
+		Default:   true,
 		StartNode: "resolver:main.default.default.dc1",
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:main.default.default.dc1": {
@@ -1589,7 +1689,7 @@ func testcase_DefaultResolver_ExternalSNI() compileTestCase {
 			}),
 		},
 	}
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: true}
+	return compileTestCase{entries: entries, expect: expect}
 }
 
 func testcase_Resolver_ExternalSNI_FailoverNotAllowed() compileTestCase {
@@ -2249,6 +2349,7 @@ func testcase_ResolverProtocolOverride() compileTestCase {
 
 	expect := &structs.CompiledDiscoveryChain{
 		Protocol:  "http2",
+		Default:   true,
 		StartNode: "resolver:main.default.default.dc1",
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:main.default.default.dc1": {
@@ -2266,7 +2367,7 @@ func testcase_ResolverProtocolOverride() compileTestCase {
 			"main.default.default.dc1": newTarget("main", "", "default", "default", "dc1", nil),
 		},
 	}
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: true,
+	return compileTestCase{entries: entries, expect: expect,
 		expectCustom: true,
 		setup: func(req *CompileRequest) {
 			req.OverrideProtocol = "http2"
@@ -2282,6 +2383,7 @@ func testcase_ResolverProtocolOverrideIgnored() compileTestCase {
 
 	expect := &structs.CompiledDiscoveryChain{
 		Protocol:  "http2",
+		Default:   true,
 		StartNode: "resolver:main.default.default.dc1",
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:main.default.default.dc1": {
@@ -2299,7 +2401,7 @@ func testcase_ResolverProtocolOverrideIgnored() compileTestCase {
 			"main.default.default.dc1": newTarget("main", "", "default", "default", "dc1", nil),
 		},
 	}
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: true,
+	return compileTestCase{entries: entries, expect: expect,
 		setup: func(req *CompileRequest) {
 			req.OverrideProtocol = "http2"
 		},
@@ -2320,6 +2422,7 @@ func testcase_RouterIgnored_ResolverProtocolOverride() compileTestCase {
 	expect := &structs.CompiledDiscoveryChain{
 		Protocol:  "tcp",
 		StartNode: "resolver:main.default.default.dc1",
+		Default:   true,
 		Nodes: map[string]*structs.DiscoveryGraphNode{
 			"resolver:main.default.default.dc1": {
 				Type: structs.DiscoveryGraphNodeTypeResolver,
@@ -2336,7 +2439,7 @@ func testcase_RouterIgnored_ResolverProtocolOverride() compileTestCase {
 			"main.default.default.dc1": newTarget("main", "", "default", "default", "dc1", nil),
 		},
 	}
-	return compileTestCase{entries: entries, expect: expect, expectIsDefault: true,
+	return compileTestCase{entries: entries, expect: expect,
 		expectCustom: true,
 		setup: func(req *CompileRequest) {
 			req.OverrideProtocol = "tcp"

agent/discovery_chain_endpoint_test.go

@@ -8,11 +8,12 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/hashicorp/consul/agent/connect"
 	"github.com/hashicorp/consul/agent/structs"
 	"github.com/hashicorp/consul/sdk/testutil/retry"
 	"github.com/hashicorp/consul/testrpc"
-	"github.com/stretchr/testify/require"
 )
 
 func TestDiscoveryChainRead(t *testing.T) {
@@ -79,6 +80,7 @@ func TestDiscoveryChainRead(t *testing.T) {
 				Partition:   "default",
 				Datacenter:  "dc1",
 				Protocol:    "tcp",
+				Default:     true,
 				StartNode:   "resolver:web.default.default.dc1",
 				Nodes: map[string]*structs.DiscoveryGraphNode{
 					"resolver:web.default.default.dc1": {
@@ -122,6 +124,7 @@ func TestDiscoveryChainRead(t *testing.T) {
 				Namespace:   "default",
 				Partition:   "default",
 				Datacenter:  "dc2",
+				Default:     true,
 				Protocol:    "tcp",
 				StartNode:   "resolver:web.default.default.dc2",
 				Nodes: map[string]*structs.DiscoveryGraphNode{
@@ -175,6 +178,7 @@ func TestDiscoveryChainRead(t *testing.T) {
 				Namespace:   "default",
 				Partition:   "default",
 				Datacenter:  "dc1",
+				Default:     true,
 				Protocol:    "tcp",
 				StartNode:   "resolver:web.default.default.dc1",
 				Nodes: map[string]*structs.DiscoveryGraphNode{

agent/proxycfg/testing_connect_proxy.go

@@ -16,7 +16,7 @@ func TestConfigSnapshot(t testing.T, nsFn func(ns *structs.NodeService), extraUp
 
 	// no entries implies we'll get a default chain
 	dbChain := discoverychain.TestCompileConfigEntries(t, "db", "default", "default", "dc1", connect.TestClusterID+".consul", nil)
-	assert.True(t, dbChain.IsDefault())
+	assert.True(t, dbChain.Default)
 
 	var (
 		upstreams   = structs.TestUpstreams(t)

agent/proxycfg/testing_ingress_gateway.go

@@ -685,10 +685,10 @@ func TestConfigSnapshotIngress_HTTPMultipleServices(t testing.T) *ConfigSnapshot
 		quxChain = discoverychain.TestCompileConfigEntries(t, "qux", "default", "default", "dc1", connect.TestClusterID+".consul", nil, entries...)
 	)
 
-	require.False(t, fooChain.IsDefault())
+	require.False(t, fooChain.Default)
-	require.False(t, barChain.IsDefault())
+	require.False(t, barChain.Default)
-	require.True(t, bazChain.IsDefault())
+	require.True(t, bazChain.Default)
-	require.True(t, quxChain.IsDefault())
+	require.True(t, quxChain.Default)
 
 	return TestConfigSnapshotIngressGateway(t, false, "http", "default", nil, func(entry *structs.IngressGatewayConfigEntry) {
 		entry.Listeners = []structs.IngressListener{

agent/structs/discovery_chain.go

@@ -26,9 +26,17 @@ type CompiledDiscoveryChain struct {
 	// non-customized versions.
 	CustomizationHash string `json:",omitempty"`
 
+	// Default indicates if this discovery chain is based on no
+	// service-resolver, service-splitter, or service-router config entries.
+	Default bool `json:",omitempty"`
+
 	// Protocol is the overall protocol shared by everything in the chain.
 	Protocol string `json:",omitempty"`
 
+	// ServiceMeta is the metadata from the underlying service-defaults config
+	// entry for the service named ServiceName.
+	ServiceMeta map[string]string `json:",omitempty"`
+
 	// StartNode is the first key into the Nodes map that should be followed
 	// when walking the discovery chain.
 	StartNode string `json:",omitempty"`
@@ -62,33 +70,6 @@ func (c *CompiledDiscoveryChain) WillFailoverThroughMeshGateway(node *DiscoveryG
 	return false
 }
 
-// IsDefault returns true if the compiled chain represents no routing, no
-// splitting, and only the default resolution.  We have to be careful here to
-// avoid returning "yep this is default" when the only resolver action being
-// applied is redirection to another resolver that is default, so we double
-// check the resolver matches the requested resolver.
-func (c *CompiledDiscoveryChain) IsDefault() bool {
-	if c.StartNode == "" || len(c.Nodes) == 0 {
-		return true
-	}
-
-	node := c.Nodes[c.StartNode]
-	if node == nil {
-		panic("not possible: missing node named '" + c.StartNode + "' in chain '" + c.ServiceName + "'")
-	}
-
-	if node.Type != DiscoveryGraphNodeTypeResolver {
-		return false
-	}
-	if !node.Resolver.Default {
-		return false
-	}
-
-	target := c.Targets[node.Resolver.Target]
-
-	return target.Service == c.ServiceName && target.Namespace == c.Namespace && target.Partition == c.Partition
-}
-
 // ID returns an ID that encodes the service, namespace, partition, and datacenter.
 // This ID allows us to compare a discovery chain target to the chain upstream itself.
 func (c *CompiledDiscoveryChain) ID() string {

agent/xds/clusters.go

@@ -612,7 +612,7 @@ func (s *ResourceGenerator) makeUpstreamClustersForDiscoveryChain(
 
 	var escapeHatchCluster *envoy_cluster_v3.Cluster
 	if cfg.EnvoyClusterJSON != "" {
-		if chain.IsDefault() {
+		if chain.Default {
 			// If you haven't done anything to setup the discovery chain, then
 			// you can use the envoy_cluster_json escape hatch.
 			escapeHatchCluster, err = makeClusterFromUserConfig(cfg.EnvoyClusterJSON)

agent/xds/endpoints.go

@@ -393,7 +393,7 @@ func (s *ResourceGenerator) endpointsFromDiscoveryChain(
 
 	var escapeHatchCluster *envoy_cluster_v3.Cluster
 	if cfg.EnvoyClusterJSON != "" {
-		if chain.IsDefault() {
+		if chain.Default {
 			// If you haven't done anything to setup the discovery chain, then
 			// you can use the envoy_cluster_json escape hatch.
 			escapeHatchCluster, err = makeClusterFromUserConfig(cfg.EnvoyClusterJSON)

agent/xds/listeners.go

@@ -115,7 +115,7 @@ func (s *ResourceGenerator) listenersFromSnapshotConnectProxy(cfgSnap *proxycfg.
 		}
 
 		// RDS, Envoy's Route Discovery Service, is only used for HTTP services with a customized discovery chain.
-		useRDS := chain.Protocol != "tcp" && !chain.IsDefault()
+		useRDS := chain.Protocol != "tcp" && !chain.Default
 
 		var clusterName string
 		if !useRDS {
@@ -1303,7 +1303,7 @@ func (s *ResourceGenerator) getAndModifyUpstreamConfigForListener(
 	if u != nil {
 		configMap = u.Config
 	}
-	if chain == nil || chain.IsDefault() {
+	if chain == nil || chain.Default {
 		cfg, err = structs.ParseUpstreamConfigNoDefaults(configMap)
 		if err != nil {
 			// Don't hard fail on a config typo, just warn. The parse func returns

agent/xds/listeners_ingress.go

@@ -48,7 +48,7 @@ func (s *ResourceGenerator) makeIngressGatewayListeners(address string, cfgSnap
 
 			// RDS, Envoy's Route Discovery Service, is only used for HTTP services with a customized discovery chain.
 			// TODO(freddy): Why can the protocol of the listener be overridden here?
-			useRDS := cfg.Protocol != "tcp" && !chain.IsDefault()
+			useRDS := cfg.Protocol != "tcp" && !chain.Default
 
 			var clusterName string
 			if !useRDS {

agent/xds/routes.go

@@ -45,7 +45,7 @@ func (s *ResourceGenerator) routesFromSnapshot(cfgSnap *proxycfg.ConfigSnapshot)
 func (s *ResourceGenerator) routesForConnectProxy(cfgSnap *proxycfg.ConfigSnapshot) ([]proto.Message, error) {
 	var resources []proto.Message
 	for uid, chain := range cfgSnap.ConnectProxy.DiscoveryChain {
-		if chain.IsDefault() {
+		if chain.Default {
 			continue
 		}
 

api/discovery_chain.go

@@ -109,9 +109,17 @@ type CompiledDiscoveryChain struct {
 	// non-customized versions.
 	CustomizationHash string
 
+	// Default indicates if this discovery chain is based on no
+	// service-resolver, service-splitter, or service-router config entries.
+	Default bool
+
 	// Protocol is the overall protocol shared by everything in the chain.
 	Protocol string
 
+	// ServiceMeta is the metadata from the underlying service-defaults config
+	// entry for the service named ServiceName.
+	ServiceMeta map[string]string
+
 	// StartNode is the first key into the Nodes map that should be followed
 	// when walking the discovery chain.
 	StartNode string

api/discovery_chain_test.go

@@ -32,6 +32,7 @@ func TestAPI_DiscoveryChain_Get(t *testing.T) {
 				Namespace:   "default",
 				Datacenter:  "dc1",
 				Protocol:    "tcp",
+				Default:     true,
 				StartNode:   "resolver:web.default.default.dc1",
 				Nodes: map[string]*DiscoveryGraphNode{
 					"resolver:web.default.default.dc1": {
@@ -72,6 +73,7 @@ func TestAPI_DiscoveryChain_Get(t *testing.T) {
 				Namespace:   "default",
 				Datacenter:  "dc2",
 				Protocol:    "tcp",
+				Default:     true,
 				StartNode:   "resolver:web.default.default.dc2",
 				Nodes: map[string]*DiscoveryGraphNode{
 					"resolver:web.default.default.dc2": {

website/content/docs/connect/l7-traffic/discovery-chain.mdx

@@ -121,9 +121,15 @@ resolved by name using the [`Targets`](#targets) field.
   balancer data plane objects to avoid sharing customized and non-customized
   versions.
 
+- `Default` `(bool: <optional>)` -  Indicates if this discovery chain is based on no
+   `service-resolver`, `service-splitter`, or `service-router` config entries.
+
 - `Protocol` `(string)` - The overall protocol shared by everything in the
   chain.
 
+- `ServiceMeta` `(map<string|string>)` - The metadata from the underlying `service-defaults` config
+   entry for the service named `ServiceName`.
+
 - `StartNode` `(string)` - The first key into the `Nodes` map that should be
   followed when traversing the discovery chain.