Add FIELD accessor support for peer metadata in tracing

extensions/common/metadata_object.h

@@ -27,9 +27,14 @@ namespace Istio {
 namespace Common {
 
 // Filter state key to store the peer metadata under.
+// CelState is stored under these keys for CEL expression support.
 constexpr absl::string_view DownstreamPeer = "downstream_peer";
 constexpr absl::string_view UpstreamPeer = "upstream_peer";
 
+// Filter state keys for WorkloadMetadataObject (FIELD accessor support).
+constexpr absl::string_view DownstreamPeerObj = "downstream_peer_obj";
+constexpr absl::string_view UpstreamPeerObj = "upstream_peer_obj";
+
 // Special filter state key to indicate the filter is done looking for peer metadata.
 // This is used by network metadata exchange on failure.
 constexpr absl::string_view NoPeer = "peer_not_found";

source/extensions/filters/http/istio_stats/istio_stats.cc

@@ -125,16 +125,25 @@ bool peerInfoRead(Reporter reporter, const StreamInfo::FilterState& filter_state
 
 std::optional<Istio::Common::WorkloadMetadataObject>
 peerInfo(Reporter reporter, const StreamInfo::FilterState& filter_state) {
-  const auto& filter_state_key =
+  const auto& cel_state_key =
       reporter == Reporter::ServerSidecar || reporter == Reporter::ServerGateway
           ? Istio::Common::DownstreamPeer
           : Istio::Common::UpstreamPeer;
-  // This's a workaround before FilterStateObject support operation like `.labels['role']`.
-  // The workaround is to use CelState to store the peer metadata.
-  // Rebuild the WorkloadMetadataObject from the CelState.
+  const auto& obj_key = reporter == Reporter::ServerSidecar || reporter == Reporter::ServerGateway
+                            ? Istio::Common::DownstreamPeerObj
+                            : Istio::Common::UpstreamPeerObj;
+
+  // Try reading as WorkloadMetadataObject first (new format, stored under *_obj key)
+  const auto* peer_info =
+      filter_state.getDataReadOnly<Istio::Common::WorkloadMetadataObject>(obj_key);
+  if (peer_info) {
+    return *peer_info;
+  }
+
+  // Fall back to CelState for backward compatibility with older deployments
   const auto* cel_state =
       filter_state.getDataReadOnly<Envoy::Extensions::Filters::Common::Expr::CelState>(
-          filter_state_key);
+          cel_state_key);
   if (!cel_state) {
     return {};
   }
@@ -144,7 +153,7 @@ peerInfo(Reporter reporter, const StreamInfo::FilterState& filter_state) {
     return {};
   }
 
-  Istio::Common::WorkloadMetadataObject peer_info(
+  Istio::Common::WorkloadMetadataObject result(
       extractString(obj, Istio::Common::InstanceNameToken),
       extractString(obj, Istio::Common::ClusterNameToken),
       extractString(obj, Istio::Common::NamespaceNameToken),
@@ -156,7 +165,17 @@ peerInfo(Reporter reporter, const StreamInfo::FilterState& filter_state) {
       Istio::Common::fromSuffix(extractString(obj, Istio::Common::WorkloadTypeToken)),
       extractString(obj, Istio::Common::IdentityToken));
 
-  return peer_info;
+  // Extract labels from the "labels" field
+  const auto& labels_it = obj.fields().find(Istio::Common::LabelsToken);
+  if (labels_it != obj.fields().end() && labels_it->second.has_struct_value()) {
+    std::vector<std::pair<std::string, std::string>> labels;
+    for (const auto& label : labels_it->second.struct_value().fields()) {
+      labels.push_back({std::string(label.first), std::string(label.second.string_value())});
+    }
+    result.setLabels(labels);
+  }
+
+  return result;
 }
 
 // Process-wide context shared with all filter instances.

source/extensions/filters/http/peer_metadata/filter.cc

@@ -291,13 +291,23 @@ void FilterConfig::setFilterState(StreamInfo::StreamInfo& info, bool downstream,
                                   const PeerInfo& value) const {
   const absl::string_view key =
       downstream ? Istio::Common::DownstreamPeer : Istio::Common::UpstreamPeer;
+  const absl::string_view obj_key =
+      downstream ? Istio::Common::DownstreamPeerObj : Istio::Common::UpstreamPeerObj;
   if (!info.filterState()->hasDataWithName(key)) {
-    // Use CelState to allow operation filter_state.upstream_peer.labels['role']
+    // Store CelState for CEL expressions like filter_state.downstream_peer.labels['role']
     auto pb = value.serializeAsProto();
-    auto peer_info = std::make_unique<CelState>(FilterConfig::peerInfoPrototype());
-    peer_info->setValue(absl::string_view(pb->SerializeAsString()));
+    auto cel_state = std::make_unique<CelState>(FilterConfig::peerInfoPrototype());
+    cel_state->setValue(absl::string_view(pb->SerializeAsString()));
     info.filterState()->setData(
-        key, std::move(peer_info), StreamInfo::FilterState::StateType::Mutable,
+        key, std::move(cel_state), StreamInfo::FilterState::StateType::Mutable,
+        StreamInfo::FilterState::LifeSpan::FilterChain, sharedWithUpstream());
+
+    // Also store WorkloadMetadataObject under a separate key for FIELD accessor support.
+    // WorkloadMetadataObject implements hasFieldSupport() + getField() for
+    // formatters using %FILTER_STATE(downstream_peer_obj:FIELD:fieldname)% syntax.
+    auto workload_metadata = std::make_unique<PeerInfo>(value);
+    info.filterState()->setData(
+        obj_key, std::move(workload_metadata), StreamInfo::FilterState::StateType::Mutable,
         StreamInfo::FilterState::LifeSpan::FilterChain, sharedWithUpstream());
   } else {
     ENVOY_LOG(debug, "Duplicate peer metadata, skipping");

source/extensions/filters/http/peer_metadata/filter_test.cc

@@ -79,13 +79,10 @@ class PeerMetadataTest : public testing::Test {
         downstream ? Istio::Common::DownstreamPeer : Istio::Common::UpstreamPeer));
   }
   void checkPeerNamespace(bool downstream, const std::string& expected) {
-    const auto* cel_state =
-        stream_info_.filterState()
-            ->getDataReadOnly<Envoy::Extensions::Filters::Common::Expr::CelState>(
-                downstream ? Istio::Common::DownstreamPeer : Istio::Common::UpstreamPeer);
-    Protobuf::Struct obj;
-    ASSERT_TRUE(obj.ParseFromString(cel_state->value().data()));
-    EXPECT_EQ(expected, extractString(obj, "namespace"));
+    const auto* peer_info = stream_info_.filterState()->getDataReadOnly<PeerInfo>(
+        downstream ? Istio::Common::DownstreamPeerObj : Istio::Common::UpstreamPeerObj);
+    ASSERT_NE(peer_info, nullptr);
+    EXPECT_EQ(expected, peer_info->namespace_name_);
   }
 
   absl::string_view extractString(const Protobuf::Struct& metadata, absl::string_view key) {
@@ -488,6 +485,81 @@ TEST_F(PeerMetadataTest, UpstreamMXPropagationSkipPassthrough) {
   checkNoPeer(false);
 }
 
+TEST_F(PeerMetadataTest, FieldAccessorSupport) {
+  const WorkloadMetadataObject pod("pod-foo-1234", "my-cluster", "default", "foo", "foo-service",
+                                   "v1alpha3", "myapp", "v1", Istio::Common::WorkloadType::Pod, "");
+  EXPECT_CALL(*metadata_provider_, GetMetadata(_))
+      .WillRepeatedly(Invoke([&](const Network::Address::InstanceConstSharedPtr& address)
+                                 -> std::optional<WorkloadMetadataObject> {
+        if (absl::StartsWith(address->asStringView(), "127.0.0.1")) {
+          return {pod};
+        }
+        return {};
+      }));
+  initialize(R"EOF(
+    downstream_discovery:
+      - workload_discovery: {}
+  )EOF");
+
+  const auto* peer_info =
+      stream_info_.filterState()->getDataReadOnly<PeerInfo>(Istio::Common::DownstreamPeerObj);
+  ASSERT_NE(peer_info, nullptr);
+
+  // Test hasFieldSupport
+  EXPECT_TRUE(peer_info->hasFieldSupport());
+
+  // Test getField() for all 9 fields
+  EXPECT_EQ("foo", std::get<absl::string_view>(peer_info->getField("workload")));
+  EXPECT_EQ("default", std::get<absl::string_view>(peer_info->getField("namespace")));
+  EXPECT_EQ("my-cluster", std::get<absl::string_view>(peer_info->getField("cluster")));
+  EXPECT_EQ("foo-service", std::get<absl::string_view>(peer_info->getField("service")));
+  EXPECT_EQ("v1alpha3", std::get<absl::string_view>(peer_info->getField("revision")));
+  EXPECT_EQ("myapp", std::get<absl::string_view>(peer_info->getField("app")));
+  EXPECT_EQ("v1", std::get<absl::string_view>(peer_info->getField("version")));
+  EXPECT_EQ("pod", std::get<absl::string_view>(peer_info->getField("type")));
+  EXPECT_EQ("pod-foo-1234", std::get<absl::string_view>(peer_info->getField("name")));
+}
+
+TEST_F(PeerMetadataTest, CelExpressionCompatibility) {
+  const WorkloadMetadataObject pod("pod-bar-5678", "test-cluster", "production", "bar",
+                                   "bar-service", "v2", "barapp", "v2",
+                                   Istio::Common::WorkloadType::Pod, "");
+  EXPECT_CALL(*metadata_provider_, GetMetadata(_))
+      .WillRepeatedly(Invoke([&](const Network::Address::InstanceConstSharedPtr& address)
+                                 -> std::optional<WorkloadMetadataObject> {
+        if (absl::StartsWith(address->asStringView(), "127.0.0.1")) {
+          return {pod};
+        }
+        return {};
+      }));
+  initialize(R"EOF(
+    downstream_discovery:
+      - workload_discovery: {}
+  )EOF");
+
+  // Verify CelState is stored under downstream_peer for CEL expressions
+  const auto* cel_state = stream_info_.filterState()
+                              ->getDataReadOnly<Envoy::Extensions::Filters::Common::Expr::CelState>(
+                                  Istio::Common::DownstreamPeer);
+  ASSERT_NE(cel_state, nullptr);
+
+  // Verify WorkloadMetadataObject is stored under downstream_peer_obj for FIELD accessor
+  const auto* peer_info =
+      stream_info_.filterState()->getDataReadOnly<PeerInfo>(Istio::Common::DownstreamPeerObj);
+  ASSERT_NE(peer_info, nullptr);
+
+  // Test that serializeAsProto still works for CEL compatibility
+  auto proto = peer_info->serializeAsProto();
+  ASSERT_NE(proto, nullptr);
+
+  // Verify the protobuf contains expected data
+  const auto* struct_proto = dynamic_cast<const google::protobuf::Struct*>(proto.get());
+  ASSERT_NE(struct_proto, nullptr);
+  EXPECT_EQ("production", extractString(*struct_proto, "namespace"));
+  EXPECT_EQ("bar", extractString(*struct_proto, "workload"));
+  EXPECT_EQ("test-cluster", extractString(*struct_proto, "cluster"));
+}
+
 } // namespace
 } // namespace PeerMetadata
 } // namespace HttpFilters