ORCA: implement ORCA RPC service for OOB backend metric reporting (#29215)

* ORCA: implement ORCA RPC service for OOB backend metric reporting

* fix unused parameter error

* gen_upb_api

* add missing build deps

* increase test timing fudge factor

* add missing copyright header

* buildifier

* don't register as a generic service

* report interval defaults to min interval

* don't regenerate the response proto unless something changed

* use INTERNAL for proto parsing failure

* use absl::Duration in public API

BUILD

@@ -229,6 +229,7 @@ GRPCXX_SRCS = [
     "src/cpp/server/health/default_health_check_service.cc",
     "src/cpp/server/health/health_check_service.cc",
     "src/cpp/server/health/health_check_service_server_builder_option.cc",
+    "src/cpp/server/orca/orca_service.cc",
     "src/cpp/server/server_builder.cc",
     "src/cpp/server/server_callback.cc",
     "src/cpp/server/server_cc.cc",
@@ -305,6 +306,7 @@ GRPCXX_PUBLIC_HDRS = [
     "include/grpcpp/create_channel.h",
     "include/grpcpp/create_channel_posix.h",
     "include/grpcpp/ext/health_check_service_server_builder_option.h",
+    "include/grpcpp/ext/orca_service.h",
     "include/grpcpp/generic/async_generic_service.h",
     "include/grpcpp/generic/generic_stub.h",
     "include/grpcpp/grpcpp.h",
@@ -4781,8 +4783,12 @@ grpc_cc_library(
         "grpc_service_config_impl",
         "grpc_trace",
         "grpc_transport_inproc",
+        "protobuf_duration_upb",
         "ref_counted",
+        "time",
         "useful",
+        "xds_orca_service_upb",
+        "xds_orca_upb",
     ],
 )
 
@@ -4815,8 +4821,12 @@ grpc_cc_library(
         "grpc_trace",
         "grpc_transport_inproc",
         "grpc_unsecure",
+        "protobuf_duration_upb",
         "ref_counted",
+        "time",
         "useful",
+        "xds_orca_service_upb",
+        "xds_orca_upb",
     ],
 )
 
@@ -5341,6 +5351,11 @@ grpc_upb_proto_library(
     deps = ["@com_github_cncf_udpa//xds/data/orca/v3:pkg"],
 )
 
+grpc_upb_proto_library(
+    name = "xds_orca_service_upb",
+    deps = ["@com_github_cncf_udpa//xds/service/orca/v3:pkg"],
+)
+
 grpc_upb_proto_library(
     name = "grpc_health_upb",
     deps = ["//src/proto/grpc/health/v1:health_proto_descriptor"],

CMakeLists.txt

@@ -568,6 +568,9 @@ protobuf_generate_grpc_cpp(
 protobuf_generate_grpc_cpp(
   src/proto/grpc/testing/xds/v3/orca_load_report.proto
 )
+protobuf_generate_grpc_cpp(
+  src/proto/grpc/testing/xds/v3/orca_service.proto
+)
 protobuf_generate_grpc_cpp(
   src/proto/grpc/testing/xds/v3/path.proto
 )
@@ -925,6 +928,7 @@ if(gRPC_BUILD_TESTS)
   add_dependencies(buildtests_cxx mock_test)
   add_dependencies(buildtests_cxx nonblocking_test)
   add_dependencies(buildtests_cxx observable_test)
+  add_dependencies(buildtests_cxx orca_service_end2end_test)
   add_dependencies(buildtests_cxx orphanable_test)
   add_dependencies(buildtests_cxx out_of_bounds_bad_client_test)
   add_dependencies(buildtests_cxx overload_test)
@@ -2859,6 +2863,19 @@ add_library(grpc++
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -2896,6 +2913,7 @@ add_library(grpc++
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
   src/cpp/server/insecure_server_credentials.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/secure_server_credentials.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
@@ -3034,6 +3052,7 @@ foreach(_hdr
   include/grpcpp/create_channel_binder.h
   include/grpcpp/create_channel_posix.h
   include/grpcpp/ext/health_check_service_server_builder_option.h
+  include/grpcpp/ext/orca_service.h
   include/grpcpp/generic/async_generic_service.h
   include/grpcpp/generic/generic_stub.h
   include/grpcpp/grpcpp.h
@@ -3526,6 +3545,19 @@ target_link_libraries(grpc++_test_util
 endif()
 
 add_library(grpc++_unsecure
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -3555,6 +3587,7 @@ add_library(grpc++_unsecure
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
   src/cpp/server/insecure_server_credentials.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc
@@ -3690,6 +3723,7 @@ foreach(_hdr
   include/grpcpp/create_channel.h
   include/grpcpp/create_channel_posix.h
   include/grpcpp/ext/health_check_service_server_builder_option.h
+  include/grpcpp/ext/orca_service.h
   include/grpcpp/generic/async_generic_service.h
   include/grpcpp/generic/generic_stub.h
   include/grpcpp/grpcpp.h
@@ -7936,6 +7970,19 @@ add_executable(binder_transport_test
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -7962,6 +8009,7 @@ add_executable(binder_transport_test
   src/cpp/server/health/default_health_check_service.cc
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc
@@ -9801,6 +9849,19 @@ add_executable(endpoint_binder_pool_test
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -9827,6 +9888,7 @@ add_executable(endpoint_binder_pool_test
   src/cpp/server/health/default_health_check_service.cc
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc
@@ -10209,6 +10271,19 @@ add_executable(fake_binder_test
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -10235,6 +10310,7 @@ add_executable(fake_binder_test
   src/cpp/server/health/default_health_check_service.cc
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc
@@ -12996,6 +13072,49 @@ target_link_libraries(observable_test
 )
 
 
+endif()
+if(gRPC_BUILD_TESTS)
+
+add_executable(orca_service_end2end_test
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.pb.cc
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.grpc.pb.cc
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.pb.h
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.grpc.pb.h
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_service.pb.cc
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_service.grpc.pb.cc
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_service.pb.h
+  ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_service.grpc.pb.h
+  test/cpp/end2end/orca_service_end2end_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+target_include_directories(orca_service_end2end_test
+  PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/include
+    ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+    ${_gRPC_RE2_INCLUDE_DIR}
+    ${_gRPC_SSL_INCLUDE_DIR}
+    ${_gRPC_UPB_GENERATED_DIR}
+    ${_gRPC_UPB_GRPC_GENERATED_DIR}
+    ${_gRPC_UPB_INCLUDE_DIR}
+    ${_gRPC_XXHASH_INCLUDE_DIR}
+    ${_gRPC_ZLIB_INCLUDE_DIR}
+    third_party/googletest/googletest/include
+    third_party/googletest/googletest
+    third_party/googletest/googlemock/include
+    third_party/googletest/googlemock
+    ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(orca_service_end2end_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc++_test_util
+)
+
+
 endif()
 if(gRPC_BUILD_TESTS)
 
@@ -16222,6 +16341,19 @@ add_executable(transport_stream_receiver_test
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -16248,6 +16380,7 @@ add_executable(transport_stream_receiver_test
   src/cpp/server/health/default_health_check_service.cc
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc
@@ -16564,6 +16697,19 @@ add_executable(wire_reader_test
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -16590,6 +16736,7 @@ add_executable(wire_reader_test
   src/cpp/server/health/default_health_check_service.cc
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc
@@ -16655,6 +16802,19 @@ add_executable(wire_writer_test
   src/core/ext/transport/binder/wire_format/transaction.cc
   src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   src/core/ext/transport/binder/wire_format/wire_writer.cc
+  src/core/ext/upb-generated/google/api/annotations.upb.c
+  src/core/ext/upb-generated/google/api/http.upb.c
+  src/core/ext/upb-generated/google/protobuf/any.upb.c
+  src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  src/core/ext/upb-generated/google/rpc/status.upb.c
+  src/core/ext/upb-generated/validate/validate.upb.c
+  src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   src/cpp/client/channel_cc.cc
   src/cpp/client/client_callback.cc
   src/cpp/client/client_context.cc
@@ -16681,6 +16841,7 @@ add_executable(wire_writer_test
   src/cpp/server/health/default_health_check_service.cc
   src/cpp/server/health/health_check_service.cc
   src/cpp/server/health/health_check_service_server_builder_option.cc
+  src/cpp/server/orca/orca_service.cc
   src/cpp/server/server_builder.cc
   src/cpp/server/server_callback.cc
   src/cpp/server/server_cc.cc

build_autogenerated.yaml

@@ -2528,6 +2528,7 @@ libs:
   - include/grpcpp/create_channel_binder.h
   - include/grpcpp/create_channel_posix.h
   - include/grpcpp/ext/health_check_service_server_builder_option.h
+  - include/grpcpp/ext/orca_service.h
   - include/grpcpp/generic/async_generic_service.h
   - include/grpcpp/generic/generic_stub.h
   - include/grpcpp/grpcpp.h
@@ -2654,6 +2655,19 @@ libs:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/client/secure_credentials.h
   - src/cpp/common/channel_filter.h
@@ -2683,6 +2697,19 @@ libs:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -2720,6 +2747,7 @@ libs:
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
   - src/cpp/server/insecure_server_credentials.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/secure_server_credentials.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
@@ -2914,6 +2942,7 @@ libs:
   - include/grpcpp/create_channel.h
   - include/grpcpp/create_channel_posix.h
   - include/grpcpp/ext/health_check_service_server_builder_option.h
+  - include/grpcpp/ext/orca_service.h
   - include/grpcpp/generic/async_generic_service.h
   - include/grpcpp/generic/generic_stub.h
   - include/grpcpp/grpcpp.h
@@ -3017,6 +3046,19 @@ libs:
   - include/grpcpp/support/time.h
   - include/grpcpp/support/validate_service_config.h
   headers:
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -3025,6 +3067,19 @@ libs:
   - src/cpp/server/thread_pool_interface.h
   - src/cpp/thread_manager/thread_manager.h
   src:
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -3054,6 +3109,7 @@ libs:
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
   - src/cpp/server/insecure_server_credentials.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc
@@ -4646,6 +4702,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -4673,6 +4742,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -4699,6 +4781,7 @@ targets:
   - src/cpp/server/health/default_health_check_service.cc
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc
@@ -5368,6 +5451,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -5395,6 +5491,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -5421,6 +5530,7 @@ targets:
   - src/cpp/server/health/default_health_check_service.cc
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc
@@ -5588,6 +5698,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -5615,6 +5738,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -5641,6 +5777,7 @@ targets:
   - src/cpp/server/health/default_health_check_service.cc
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc
@@ -6647,6 +6784,17 @@ targets:
   - absl/types:variant
   - gpr
   uses_polling: false
+- name: orca_service_end2end_test
+  gtest: true
+  build: test
+  language: c++
+  headers: []
+  src:
+  - src/proto/grpc/testing/xds/v3/orca_load_report.proto
+  - src/proto/grpc/testing/xds/v3/orca_service.proto
+  - test/cpp/end2end/orca_service_end2end_test.cc
+  deps:
+  - grpc++_test_util
 - name: orphanable_test
   gtest: true
   build: test
@@ -7897,6 +8045,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -7923,6 +8084,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -7949,6 +8123,7 @@ targets:
   - src/cpp/server/health/default_health_check_service.cc
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc
@@ -8085,6 +8260,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -8112,6 +8300,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -8138,6 +8339,7 @@ targets:
   - src/cpp/server/health/default_health_check_service.cc
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc
@@ -8179,6 +8381,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/wire_reader.h
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.h
   - src/core/ext/transport/binder/wire_format/wire_writer.h
+  - src/core/ext/upb-generated/google/api/annotations.upb.h
+  - src/core/ext/upb-generated/google/api/http.upb.h
+  - src/core/ext/upb-generated/google/protobuf/any.upb.h
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.h
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.h
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.h
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.h
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.h
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.h
+  - src/core/ext/upb-generated/google/rpc/status.upb.h
+  - src/core/ext/upb-generated/validate/validate.upb.h
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h
   - src/cpp/client/create_channel_internal.h
   - src/cpp/common/channel_filter.h
   - src/cpp/server/dynamic_thread_pool.h
@@ -8206,6 +8421,19 @@ targets:
   - src/core/ext/transport/binder/wire_format/transaction.cc
   - src/core/ext/transport/binder/wire_format/wire_reader_impl.cc
   - src/core/ext/transport/binder/wire_format/wire_writer.cc
+  - src/core/ext/upb-generated/google/api/annotations.upb.c
+  - src/core/ext/upb-generated/google/api/http.upb.c
+  - src/core/ext/upb-generated/google/protobuf/any.upb.c
+  - src/core/ext/upb-generated/google/protobuf/descriptor.upb.c
+  - src/core/ext/upb-generated/google/protobuf/duration.upb.c
+  - src/core/ext/upb-generated/google/protobuf/empty.upb.c
+  - src/core/ext/upb-generated/google/protobuf/struct.upb.c
+  - src/core/ext/upb-generated/google/protobuf/timestamp.upb.c
+  - src/core/ext/upb-generated/google/protobuf/wrappers.upb.c
+  - src/core/ext/upb-generated/google/rpc/status.upb.c
+  - src/core/ext/upb-generated/validate/validate.upb.c
+  - src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c
+  - src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c
   - src/cpp/client/channel_cc.cc
   - src/cpp/client/client_callback.cc
   - src/cpp/client/client_context.cc
@@ -8232,6 +8460,7 @@ targets:
   - src/cpp/server/health/default_health_check_service.cc
   - src/cpp/server/health/health_check_service.cc
   - src/cpp/server/health/health_check_service_server_builder_option.cc
+  - src/cpp/server/orca/orca_service.cc
   - src/cpp/server/server_builder.cc
   - src/cpp/server/server_callback.cc
   - src/cpp/server/server_cc.cc

gRPC-C++.podspec

@@ -87,6 +87,7 @@ Pod::Spec.new do |s|
                       'include/grpcpp/create_channel_binder.h',
                       'include/grpcpp/create_channel_posix.h',
                       'include/grpcpp/ext/health_check_service_server_builder_option.h',
+                      'include/grpcpp/ext/orca_service.h',
                       'include/grpcpp/generic/async_generic_service.h',
                       'include/grpcpp/generic/generic_stub.h',
                       'include/grpcpp/grpcpp.h',
@@ -473,6 +474,8 @@ Pod::Spec.new do |s|
                       'src/core/ext/upb-generated/xds/core/v3/resource_locator.upb.h',
                       'src/core/ext/upb-generated/xds/core/v3/resource_name.upb.h',
                       'src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h',
+                      'src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c',
+                      'src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h',
                       'src/core/ext/upb-generated/xds/type/matcher/v3/matcher.upb.h',
                       'src/core/ext/upb-generated/xds/type/matcher/v3/regex.upb.h',
                       'src/core/ext/upb-generated/xds/type/matcher/v3/string.upb.h',
@@ -980,6 +983,7 @@ Pod::Spec.new do |s|
                       'src/cpp/server/health/health_check_service.cc',
                       'src/cpp/server/health/health_check_service_server_builder_option.cc',
                       'src/cpp/server/insecure_server_credentials.cc',
+                      'src/cpp/server/orca/orca_service.cc',
                       'src/cpp/server/secure_server_credentials.cc',
                       'src/cpp/server/secure_server_credentials.h',
                       'src/cpp/server/server_builder.cc',
@@ -1284,6 +1288,7 @@ Pod::Spec.new do |s|
                               'src/core/ext/upb-generated/xds/core/v3/resource_locator.upb.h',
                               'src/core/ext/upb-generated/xds/core/v3/resource_name.upb.h',
                               'src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h',
+                              'src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h',
                               'src/core/ext/upb-generated/xds/type/matcher/v3/matcher.upb.h',
                               'src/core/ext/upb-generated/xds/type/matcher/v3/regex.upb.h',
                               'src/core/ext/upb-generated/xds/type/matcher/v3/string.upb.h',

grpc.gyp

@@ -1479,6 +1479,19 @@
         'src/core/ext/transport/binder/wire_format/transaction.cc',
         'src/core/ext/transport/binder/wire_format/wire_reader_impl.cc',
         'src/core/ext/transport/binder/wire_format/wire_writer.cc',
+        'src/core/ext/upb-generated/google/api/annotations.upb.c',
+        'src/core/ext/upb-generated/google/api/http.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/any.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/descriptor.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/duration.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/empty.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/struct.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/timestamp.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/wrappers.upb.c',
+        'src/core/ext/upb-generated/google/rpc/status.upb.c',
+        'src/core/ext/upb-generated/validate/validate.upb.c',
+        'src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c',
+        'src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c',
         'src/cpp/client/channel_cc.cc',
         'src/cpp/client/client_callback.cc',
         'src/cpp/client/client_context.cc',
@@ -1516,6 +1529,7 @@
         'src/cpp/server/health/health_check_service.cc',
         'src/cpp/server/health/health_check_service_server_builder_option.cc',
         'src/cpp/server/insecure_server_credentials.cc',
+        'src/cpp/server/orca/orca_service.cc',
         'src/cpp/server/secure_server_credentials.cc',
         'src/cpp/server/server_builder.cc',
         'src/cpp/server/server_callback.cc',
@@ -1612,6 +1626,19 @@
         'grpc_unsecure',
       ],
       'sources': [
+        'src/core/ext/upb-generated/google/api/annotations.upb.c',
+        'src/core/ext/upb-generated/google/api/http.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/any.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/descriptor.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/duration.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/empty.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/struct.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/timestamp.upb.c',
+        'src/core/ext/upb-generated/google/protobuf/wrappers.upb.c',
+        'src/core/ext/upb-generated/google/rpc/status.upb.c',
+        'src/core/ext/upb-generated/validate/validate.upb.c',
+        'src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c',
+        'src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c',
         'src/cpp/client/channel_cc.cc',
         'src/cpp/client/client_callback.cc',
         'src/cpp/client/client_context.cc',
@@ -1641,6 +1668,7 @@
         'src/cpp/server/health/health_check_service.cc',
         'src/cpp/server/health/health_check_service_server_builder_option.cc',
         'src/cpp/server/insecure_server_credentials.cc',
+        'src/cpp/server/orca/orca_service.cc',
         'src/cpp/server/server_builder.cc',
         'src/cpp/server/server_callback.cc',
         'src/cpp/server/server_cc.cc',

include/grpcpp/ext/orca_service.h

@@ -0,0 +1,83 @@
+//
+// Copyright 2022 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.
+//
+
+#ifndef GRPCPP_EXT_ORCA_SERVICE_H
+#define GRPCPP_EXT_ORCA_SERVICE_H
+
+#include <map>
+#include <string>
+
+#include "absl/time/time.h"
+#include "absl/types/optional.h"
+
+#include <grpcpp/impl/codegen/server_callback.h>
+#include <grpcpp/impl/codegen/service_type.h>
+#include <grpcpp/impl/codegen/sync.h>
+#include <grpcpp/server_builder.h>
+#include <grpcpp/support/slice.h>
+
+namespace grpc {
+namespace experimental {
+
+// RPC service implementation for supplying out-of-band backend
+// utilization metrics to clients.
+class OrcaService : public Service {
+ public:
+  struct Options {
+    // Minimum report interval.  If a client requests an interval lower
+    // than this value, this value will be used instead.
+    absl::Duration min_report_duration = absl::Seconds(30);
+
+    Options() = default;
+    Options& set_min_report_duration(absl::Duration duration) {
+      min_report_duration = duration;
+      return *this;
+    }
+  };
+
+  explicit OrcaService(Options options);
+
+  // Sets or removes the CPU utilization value to be reported to clients.
+  void SetCpuUtilization(double cpu_utilization);
+  void DeleteCpuUtilization();
+
+  // Sets of removes the memory utilization value to be reported to clients.
+  void SetMemoryUtilization(double memory_utilization);
+  void DeleteMemoryUtilization();
+
+  // Sets or removed named utilization values to be reported to clients.
+  void SetNamedUtilization(std::string name, double utilization);
+  void DeleteNamedUtilization(const std::string& name);
+  void SetAllNamedUtilization(std::map<std::string, double> named_utilization);
+
+ private:
+  class Reactor;
+
+  Slice GetOrCreateSerializedResponse();
+
+  const absl::Duration min_report_duration_;
+
+  grpc::internal::Mutex mu_;
+  double cpu_utilization_ ABSL_GUARDED_BY(&mu_) = -1;
+  double memory_utilization_ ABSL_GUARDED_BY(&mu_) = -1;
+  std::map<std::string, double> named_utilization_ ABSL_GUARDED_BY(&mu_);
+  absl::optional<Slice> response_slice_ ABSL_GUARDED_BY(&mu_);
+};
+
+}  // namespace experimental
+}  // namespace grpc
+
+#endif  // GRPCPP_EXT_ORCA_SERVICE_H

src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c

@@ -0,0 +1,47 @@
+/* This file was generated by upbc (the upb compiler) from the input
+ * file:
+ *
+ *     xds/service/orca/v3/orca.proto
+ *
+ * Do not edit -- your changes will be discarded when the file is
+ * regenerated. */
+
+#include <stddef.h>
+#include "upb/msg_internal.h"
+#include "xds/service/orca/v3/orca.upb.h"
+#include "xds/data/orca/v3/orca_load_report.upb.h"
+#include "google/protobuf/duration.upb.h"
+#include "validate/validate.upb.h"
+
+#include "upb/port_def.inc"
+
+static const upb_MiniTable_Sub xds_service_orca_v3_OrcaLoadReportRequest_submsgs[1] = {
+  {.submsg = &google_protobuf_Duration_msginit},
+};
+
+static const upb_MiniTable_Field xds_service_orca_v3_OrcaLoadReportRequest__fields[2] = {
+  {1, UPB_SIZE(4, 8), 1, 0, 11, kUpb_FieldMode_Scalar | (upb_FieldRep_Pointer << upb_FieldRep_Shift)},
+  {2, UPB_SIZE(8, 16), 0, 0, 9, kUpb_FieldMode_Array | (upb_FieldRep_Pointer << upb_FieldRep_Shift)},
+};
+
+const upb_MiniTable xds_service_orca_v3_OrcaLoadReportRequest_msginit = {
+  &xds_service_orca_v3_OrcaLoadReportRequest_submsgs[0],
+  &xds_service_orca_v3_OrcaLoadReportRequest__fields[0],
+  UPB_SIZE(16, 24), 2, upb_ExtMode_NonExtendable, 2, 255, 0,
+};
+
+static const upb_MiniTable *messages_layout[1] = {
+  &xds_service_orca_v3_OrcaLoadReportRequest_msginit,
+};
+
+const upb_MiniTable_File xds_service_orca_v3_orca_proto_upb_file_layout = {
+  messages_layout,
+  NULL,
+  NULL,
+  1,
+  0,
+  0,
+};
+
+#include "upb/port_undef.inc"
+

src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h

@@ -0,0 +1,100 @@
+/* This file was generated by upbc (the upb compiler) from the input
+ * file:
+ *
+ *     xds/service/orca/v3/orca.proto
+ *
+ * Do not edit -- your changes will be discarded when the file is
+ * regenerated. */
+
+#ifndef XDS_SERVICE_ORCA_V3_ORCA_PROTO_UPB_H_
+#define XDS_SERVICE_ORCA_V3_ORCA_PROTO_UPB_H_
+
+#include "upb/msg_internal.h"
+#include "upb/decode.h"
+#include "upb/decode_fast.h"
+#include "upb/encode.h"
+
+#include "upb/port_def.inc"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct xds_service_orca_v3_OrcaLoadReportRequest;
+typedef struct xds_service_orca_v3_OrcaLoadReportRequest xds_service_orca_v3_OrcaLoadReportRequest;
+extern const upb_MiniTable xds_service_orca_v3_OrcaLoadReportRequest_msginit;
+struct google_protobuf_Duration;
+extern const upb_MiniTable google_protobuf_Duration_msginit;
+
+
+
+/* xds.service.orca.v3.OrcaLoadReportRequest */
+
+UPB_INLINE xds_service_orca_v3_OrcaLoadReportRequest* xds_service_orca_v3_OrcaLoadReportRequest_new(upb_Arena* arena) {
+  return (xds_service_orca_v3_OrcaLoadReportRequest*)_upb_Message_New(&xds_service_orca_v3_OrcaLoadReportRequest_msginit, arena);
+}
+UPB_INLINE xds_service_orca_v3_OrcaLoadReportRequest* xds_service_orca_v3_OrcaLoadReportRequest_parse(const char* buf, size_t size, upb_Arena* arena) {
+  xds_service_orca_v3_OrcaLoadReportRequest* ret = xds_service_orca_v3_OrcaLoadReportRequest_new(arena);
+  if (!ret) return NULL;
+  if (upb_Decode(buf, size, ret, &xds_service_orca_v3_OrcaLoadReportRequest_msginit, NULL, 0, arena) != kUpb_DecodeStatus_Ok) {
+    return NULL;
+  }
+  return ret;
+}
+UPB_INLINE xds_service_orca_v3_OrcaLoadReportRequest* xds_service_orca_v3_OrcaLoadReportRequest_parse_ex(const char* buf, size_t size,
+                           const upb_ExtensionRegistry* extreg,
+                           int options, upb_Arena* arena) {
+  xds_service_orca_v3_OrcaLoadReportRequest* ret = xds_service_orca_v3_OrcaLoadReportRequest_new(arena);
+  if (!ret) return NULL;
+  if (upb_Decode(buf, size, ret, &xds_service_orca_v3_OrcaLoadReportRequest_msginit, extreg, options, arena) !=
+      kUpb_DecodeStatus_Ok) {
+    return NULL;
+  }
+  return ret;
+}
+UPB_INLINE char* xds_service_orca_v3_OrcaLoadReportRequest_serialize(const xds_service_orca_v3_OrcaLoadReportRequest* msg, upb_Arena* arena, size_t* len) {
+  return upb_Encode(msg, &xds_service_orca_v3_OrcaLoadReportRequest_msginit, 0, arena, len);
+}
+UPB_INLINE char* xds_service_orca_v3_OrcaLoadReportRequest_serialize_ex(const xds_service_orca_v3_OrcaLoadReportRequest* msg, int options,
+                                 upb_Arena* arena, size_t* len) {
+  return upb_Encode(msg, &xds_service_orca_v3_OrcaLoadReportRequest_msginit, options, arena, len);
+}
+UPB_INLINE bool xds_service_orca_v3_OrcaLoadReportRequest_has_report_interval(const xds_service_orca_v3_OrcaLoadReportRequest *msg) { return _upb_hasbit(msg, 1); }
+UPB_INLINE const struct google_protobuf_Duration* xds_service_orca_v3_OrcaLoadReportRequest_report_interval(const xds_service_orca_v3_OrcaLoadReportRequest* msg) {
+  return *UPB_PTR_AT(msg, UPB_SIZE(4, 8), const struct google_protobuf_Duration*);
+}
+UPB_INLINE upb_StringView const* xds_service_orca_v3_OrcaLoadReportRequest_request_cost_names(const xds_service_orca_v3_OrcaLoadReportRequest *msg, size_t *len) { return (upb_StringView const*)_upb_array_accessor(msg, UPB_SIZE(8, 16), len); }
+
+UPB_INLINE void xds_service_orca_v3_OrcaLoadReportRequest_set_report_interval(xds_service_orca_v3_OrcaLoadReportRequest *msg, struct google_protobuf_Duration* value) {
+  _upb_sethas(msg, 1);
+  *UPB_PTR_AT(msg, UPB_SIZE(4, 8), struct google_protobuf_Duration*) = value;
+}
+UPB_INLINE struct google_protobuf_Duration* xds_service_orca_v3_OrcaLoadReportRequest_mutable_report_interval(xds_service_orca_v3_OrcaLoadReportRequest *msg, upb_Arena *arena) {
+  struct google_protobuf_Duration* sub = (struct google_protobuf_Duration*)xds_service_orca_v3_OrcaLoadReportRequest_report_interval(msg);
+  if (sub == NULL) {
+    sub = (struct google_protobuf_Duration*)_upb_Message_New(&google_protobuf_Duration_msginit, arena);
+    if (!sub) return NULL;
+    xds_service_orca_v3_OrcaLoadReportRequest_set_report_interval(msg, sub);
+  }
+  return sub;
+}
+UPB_INLINE upb_StringView* xds_service_orca_v3_OrcaLoadReportRequest_mutable_request_cost_names(xds_service_orca_v3_OrcaLoadReportRequest *msg, size_t *len) {
+  return (upb_StringView*)_upb_array_mutable_accessor(msg, UPB_SIZE(8, 16), len);
+}
+UPB_INLINE upb_StringView* xds_service_orca_v3_OrcaLoadReportRequest_resize_request_cost_names(xds_service_orca_v3_OrcaLoadReportRequest *msg, size_t len, upb_Arena *arena) {
+  return (upb_StringView*)_upb_Array_Resize_accessor2(msg, UPB_SIZE(8, 16), len, UPB_SIZE(3, 4), arena);
+}
+UPB_INLINE bool xds_service_orca_v3_OrcaLoadReportRequest_add_request_cost_names(xds_service_orca_v3_OrcaLoadReportRequest *msg, upb_StringView val, upb_Arena *arena) {
+  return _upb_Array_Append_accessor2(msg, UPB_SIZE(8, 16), UPB_SIZE(3, 4), &val,
+      arena);
+}
+
+extern const upb_MiniTable_File xds_service_orca_v3_orca_proto_upb_file_layout;
+
+#ifdef __cplusplus
+}  /* extern "C" */
+#endif
+
+#include "upb/port_undef.inc"
+
+#endif  /* XDS_SERVICE_ORCA_V3_ORCA_PROTO_UPB_H_ */

src/cpp/server/orca/orca_service.cc

@@ -0,0 +1,224 @@
+//
+// Copyright 2022 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.
+//
+
+#include "google/protobuf/duration.upb.h"
+#include "upb/upb.hpp"
+#include "xds/data/orca/v3/orca_load_report.upb.h"
+#include "xds/service/orca/v3/orca.upb.h"
+
+#include <grpcpp/ext/orca_service.h>
+#include <grpcpp/impl/codegen/server_callback_handlers.h>
+
+#include "src/core/lib/gprpp/time.h"
+#include "src/core/lib/iomgr/timer.h"
+
+namespace grpc {
+namespace experimental {
+
+//
+// OrcaService::Reactor
+//
+
+class OrcaService::Reactor : public ServerWriteReactor<ByteBuffer>,
+                             public grpc_core::RefCounted<Reactor> {
+ public:
+  explicit Reactor(OrcaService* service, const ByteBuffer* request_buffer)
+      : service_(service) {
+    GRPC_CLOSURE_INIT(&on_timer_, OnTimer, this, nullptr);
+    // Get slice from request.
+    Slice slice;
+    request_buffer->DumpToSingleSlice(&slice);
+    // Parse request proto.
+    upb::Arena arena;
+    xds_service_orca_v3_OrcaLoadReportRequest* request =
+        xds_service_orca_v3_OrcaLoadReportRequest_parse(
+            reinterpret_cast<const char*>(slice.begin()), slice.size(),
+            arena.ptr());
+    if (request == nullptr) {
+      Finish(Status(StatusCode::INTERNAL, "could not parse request proto"));
+      return;
+    }
+    const auto* duration_proto =
+        xds_service_orca_v3_OrcaLoadReportRequest_report_interval(request);
+    if (duration_proto != nullptr) {
+      report_interval_ = grpc_core::Duration::FromSecondsAndNanoseconds(
+          google_protobuf_Duration_seconds(duration_proto),
+          google_protobuf_Duration_nanos(duration_proto));
+    }
+    auto min_interval = grpc_core::Duration::Milliseconds(
+        service_->min_report_duration_ / absl::Milliseconds(1));
+    if (report_interval_ < min_interval) report_interval_ = min_interval;
+    // Send initial response.
+    SendResponse();
+  }
+
+  void OnWriteDone(bool ok) override {
+    if (!ok) {
+      Finish(Status(StatusCode::UNKNOWN, "write failed"));
+      return;
+    }
+    response_.Clear();
+    ScheduleTimer();
+  }
+
+  void OnCancel() override {
+    MaybeCancelTimer();
+    Finish(Status(StatusCode::UNKNOWN, "call cancelled by client"));
+  }
+
+  void OnDone() override {
+    // Free the initial ref from instantiation.
+    Unref();
+  }
+
+ private:
+  void SendResponse() {
+    Slice response_slice = service_->GetOrCreateSerializedResponse();
+    ByteBuffer response_buffer(&response_slice, 1);
+    response_.Swap(&response_buffer);
+    StartWrite(&response_);
+  }
+
+  void ScheduleTimer() {
+    grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
+    grpc_core::ExecCtx exec_ctx;
+    Ref().release();  // Ref held by timer.
+    grpc::internal::MutexLock lock(&timer_mu_);
+    timer_pending_ = true;
+    grpc_timer_init(&timer_, exec_ctx.Now() + report_interval_, &on_timer_);
+  }
+
+  void MaybeCancelTimer() {
+    grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
+    grpc_core::ExecCtx exec_ctx;
+    grpc::internal::MutexLock lock(&timer_mu_);
+    if (timer_pending_) {
+      timer_pending_ = false;
+      grpc_timer_cancel(&timer_);
+    }
+  }
+
+  static void OnTimer(void* arg, grpc_error_handle error) {
+    grpc_core::RefCountedPtr<Reactor> self(static_cast<Reactor*>(arg));
+    grpc::internal::MutexLock lock(&self->timer_mu_);
+    if (error == GRPC_ERROR_NONE && self->timer_pending_) {
+      self->timer_pending_ = false;
+      self->SendResponse();
+    }
+  }
+
+  OrcaService* service_;
+
+  // TODO(roth): Change this to use the EventEngine API once it becomes
+  // available.
+  grpc::internal::Mutex timer_mu_;
+  bool timer_pending_ ABSL_GUARDED_BY(&timer_mu_) = false;
+  grpc_timer timer_ ABSL_GUARDED_BY(&timer_mu_);
+  grpc_closure on_timer_;
+
+  grpc_core::Duration report_interval_;
+  ByteBuffer response_;
+};
+
+//
+// OrcaService
+//
+
+OrcaService::OrcaService(OrcaService::Options options)
+    : min_report_duration_(options.min_report_duration) {
+  AddMethod(new internal::RpcServiceMethod(
+      "/xds.service.orca.v3.OpenRcaService/StreamCoreMetrics",
+      internal::RpcMethod::SERVER_STREAMING, /*handler=*/nullptr));
+  MarkMethodCallback(
+      0, new internal::CallbackServerStreamingHandler<ByteBuffer, ByteBuffer>(
+             [this](CallbackServerContext* /*ctx*/, const ByteBuffer* request) {
+               return new Reactor(this, request);
+             }));
+}
+
+void OrcaService::SetCpuUtilization(double cpu_utilization) {
+  grpc::internal::MutexLock lock(&mu_);
+  cpu_utilization_ = cpu_utilization;
+  response_slice_.reset();
+}
+
+void OrcaService::DeleteCpuUtilization() {
+  grpc::internal::MutexLock lock(&mu_);
+  cpu_utilization_ = -1;
+  response_slice_.reset();
+}
+
+void OrcaService::SetMemoryUtilization(double memory_utilization) {
+  grpc::internal::MutexLock lock(&mu_);
+  memory_utilization_ = memory_utilization;
+  response_slice_.reset();
+}
+
+void OrcaService::DeleteMemoryUtilization() {
+  grpc::internal::MutexLock lock(&mu_);
+  memory_utilization_ = -1;
+  response_slice_.reset();
+}
+
+void OrcaService::SetNamedUtilization(std::string name, double utilization) {
+  grpc::internal::MutexLock lock(&mu_);
+  named_utilization_[std::move(name)] = utilization;
+  response_slice_.reset();
+}
+
+void OrcaService::DeleteNamedUtilization(const std::string& name) {
+  grpc::internal::MutexLock lock(&mu_);
+  named_utilization_.erase(name);
+  response_slice_.reset();
+}
+
+void OrcaService::SetAllNamedUtilization(
+    std::map<std::string, double> named_utilization) {
+  grpc::internal::MutexLock lock(&mu_);
+  named_utilization_ = std::move(named_utilization);
+  response_slice_.reset();
+}
+
+Slice OrcaService::GetOrCreateSerializedResponse() {
+  grpc::internal::MutexLock lock(&mu_);
+  if (!response_slice_.has_value()) {
+    upb::Arena arena;
+    xds_data_orca_v3_OrcaLoadReport* response =
+        xds_data_orca_v3_OrcaLoadReport_new(arena.ptr());
+    if (cpu_utilization_ != -1) {
+      xds_data_orca_v3_OrcaLoadReport_set_cpu_utilization(response,
+                                                          cpu_utilization_);
+    }
+    if (memory_utilization_ != -1) {
+      xds_data_orca_v3_OrcaLoadReport_set_mem_utilization(response,
+                                                          memory_utilization_);
+    }
+    for (const auto& p : named_utilization_) {
+      xds_data_orca_v3_OrcaLoadReport_utilization_set(
+          response,
+          upb_StringView_FromDataAndSize(p.first.data(), p.first.size()),
+          p.second, arena.ptr());
+    }
+    size_t buf_length;
+    char* buf = xds_data_orca_v3_OrcaLoadReport_serialize(response, arena.ptr(),
+                                                          &buf_length);
+    response_slice_.emplace(buf, buf_length);
+  }
+  return Slice(*response_slice_);
+}
+
+}  // namespace experimental
+}  // namespace grpc

src/proto/grpc/testing/xds/v3/BUILD

@@ -167,6 +167,18 @@ grpc_proto_library(
     ],
 )
 
+grpc_proto_library(
+    name = "orca_service_proto",
+    srcs = [
+        "orca_service.proto",
+    ],
+    has_services = True,
+    well_known_protos = True,
+    deps = [
+        "orca_load_report_proto",
+    ],
+)
+
 grpc_proto_library(
     name = "protocol_proto",
     srcs = [

src/proto/grpc/testing/xds/v3/orca_service.proto

@@ -0,0 +1,47 @@
+// Copyright 2022 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.
+
+// Local copy of Envoy xDS proto file, used for testing only.
+
+syntax = "proto3";
+
+package xds.service.orca.v3;
+
+import "src/proto/grpc/testing/xds/v3/orca_load_report.proto";
+
+import "google/protobuf/duration.proto";
+
+// See section `Out-of-band (OOB) reporting` of the design document in
+// :ref:`https://github.com/envoyproxy/envoy/issues/6614`.
+
+// Out-of-band (OOB) load reporting service for the additional load reporting
+// agent that does not sit in the request path. Reports are periodically sampled
+// with sufficient frequency to provide temporal association with requests.
+// OOB reporting compensates the limitation of in-band reporting in revealing
+// costs for backends that do not provide a steady stream of telemetry such as
+// long running stream operations and zero QPS services. This is a server
+// streaming service, client needs to terminate current RPC and initiate
+// a new call to change backend reporting frequency.
+service OpenRcaService {
+  rpc StreamCoreMetrics(OrcaLoadReportRequest) returns (stream xds.data.orca.v3.OrcaLoadReport);
+}
+
+message OrcaLoadReportRequest {
+  // Interval for generating Open RCA core metric responses.
+  google.protobuf.Duration report_interval = 1;
+  // Request costs to collect. If this is empty, all known requests costs tracked by
+  // the load reporting agent will be returned. This provides an opportunity for
+  // the client to selectively obtain a subset of tracked costs.
+  repeated string request_cost_names = 2;
+}

test/cpp/end2end/BUILD

@@ -928,3 +928,17 @@ grpc_cc_test(
         "//test/cpp/util:test_util",
     ],
 )
+
+grpc_cc_test(
+    name = "orca_service_end2end_test",
+    srcs = ["orca_service_end2end_test.cc"],
+    external_deps = [
+        "gtest",
+    ],
+    deps = [
+        "//:grpc++",
+        "//src/proto/grpc/testing/xds/v3:orca_service_proto",
+        "//test/core/util:grpc_test_util",
+        "//test/cpp/util:test_util",
+    ],
+)

test/cpp/end2end/orca_service_end2end_test.cc

@@ -0,0 +1,200 @@
+//
+// Copyright 2022 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.
+//
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "absl/strings/str_cat.h"
+#include "absl/types/optional.h"
+
+#include <grpc/grpc.h>
+#include <grpcpp/channel.h>
+#include <grpcpp/client_context.h>
+#include <grpcpp/create_channel.h>
+#include <grpcpp/ext/orca_service.h>
+#include <grpcpp/server.h>
+#include <grpcpp/server_builder.h>
+#include <grpcpp/server_context.h>
+
+#include "src/core/lib/gprpp/time.h"
+#include "src/proto/grpc/testing/xds/v3/orca_service.grpc.pb.h"
+#include "src/proto/grpc/testing/xds/v3/orca_service.pb.h"
+#include "test/core/util/port.h"
+#include "test/core/util/test_config.h"
+
+using xds::data::orca::v3::OrcaLoadReport;
+using xds::service::orca::v3::OpenRcaService;
+using xds::service::orca::v3::OrcaLoadReportRequest;
+
+namespace grpc {
+namespace testing {
+namespace {
+
+using experimental::OrcaService;
+
+class OrcaServiceEnd2endTest : public ::testing::Test {
+ protected:
+  // A wrapper for the client stream that ensures that responses come
+  // back at the requested interval.
+  class Stream {
+   public:
+    Stream(OpenRcaService::Stub* stub, grpc_core::Duration requested_interval)
+        : requested_interval_(requested_interval) {
+      OrcaLoadReportRequest request;
+      gpr_timespec timespec = requested_interval.as_timespec();
+      auto* interval_proto = request.mutable_report_interval();
+      interval_proto->set_seconds(timespec.tv_sec);
+      interval_proto->set_nanos(timespec.tv_nsec);
+      stream_ = stub->StreamCoreMetrics(&context_, request);
+    }
+
+    ~Stream() { context_.TryCancel(); }
+
+    OrcaLoadReport ReadResponse() {
+      OrcaLoadReport response;
+      EXPECT_TRUE(stream_->Read(&response));
+      auto now = grpc_core::Timestamp::FromTimespecRoundDown(
+          gpr_now(GPR_CLOCK_MONOTONIC));
+      if (last_response_time_.has_value()) {
+        // Allow a small fudge factor to avoid test flakiness.
+        const grpc_core::Duration fudge_factor =
+            grpc_core::Duration::Milliseconds(50) * grpc_test_slowdown_factor();
+        auto elapsed = now - *last_response_time_;
+        EXPECT_GE(elapsed, requested_interval_ - fudge_factor)
+            << elapsed.ToString();
+        EXPECT_LE(elapsed, requested_interval_ + fudge_factor)
+            << elapsed.ToString();
+      }
+      last_response_time_ = now;
+      return response;
+    }
+
+   private:
+    const grpc_core::Duration requested_interval_;
+    ClientContext context_;
+    std::unique_ptr<grpc::ClientReaderInterface<OrcaLoadReport>> stream_;
+    absl::optional<grpc_core::Timestamp> last_response_time_;
+  };
+
+  OrcaServiceEnd2endTest()
+      : orca_service_(OrcaService::Options().set_min_report_duration(
+            absl::ZeroDuration())) {
+    std::string server_address =
+        absl::StrCat("localhost:", grpc_pick_unused_port_or_die());
+    ServerBuilder builder;
+    builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
+    builder.RegisterService(&orca_service_);
+    server_ = builder.BuildAndStart();
+    gpr_log(GPR_INFO, "server started on %s", server_address_.c_str());
+    auto channel = CreateChannel(server_address, InsecureChannelCredentials());
+    stub_ = OpenRcaService::NewStub(channel);
+  }
+
+  ~OrcaServiceEnd2endTest() override { server_->Shutdown(); }
+
+  std::string server_address_;
+  OrcaService orca_service_;
+  std::unique_ptr<Server> server_;
+  std::unique_ptr<OpenRcaService::Stub> stub_;
+};
+
+TEST_F(OrcaServiceEnd2endTest, Basic) {
+  constexpr char kMetricName1[] = "foo";
+  constexpr char kMetricName2[] = "bar";
+  constexpr char kMetricName3[] = "baz";
+  constexpr char kMetricName4[] = "quux";
+  // Start stream1 with 5s interval and stream2 with 2.5s interval.
+  // Throughout the test, we should get two responses on stream2 for
+  // every one response on stream1.
+  Stream stream1(stub_.get(), grpc_core::Duration::Milliseconds(5000));
+  Stream stream2(stub_.get(), grpc_core::Duration::Milliseconds(2500));
+  auto ReadResponses = [&](std::function<void(const OrcaLoadReport&)> checker) {
+    gpr_log(GPR_INFO, "reading response from stream1");
+    OrcaLoadReport response = stream1.ReadResponse();
+    checker(response);
+    gpr_log(GPR_INFO, "reading response from stream2");
+    response = stream2.ReadResponse();
+    checker(response);
+    gpr_log(GPR_INFO, "reading response from stream2");
+    response = stream2.ReadResponse();
+    checker(response);
+  };
+  // Initial response should not have any values populated.
+  ReadResponses([](const OrcaLoadReport& response) {
+    EXPECT_EQ(response.cpu_utilization(), 0);
+    EXPECT_EQ(response.mem_utilization(), 0);
+    EXPECT_THAT(response.utilization(), ::testing::UnorderedElementsAre());
+  });
+  // Now set CPU utilization on the server.
+  orca_service_.SetCpuUtilization(0.5);
+  ReadResponses([](const OrcaLoadReport& response) {
+    EXPECT_EQ(response.cpu_utilization(), 0.5);
+    EXPECT_EQ(response.mem_utilization(), 0);
+    EXPECT_THAT(response.utilization(), ::testing::UnorderedElementsAre());
+  });
+  // Update CPU utilization and set memory utilization.
+  orca_service_.SetCpuUtilization(0.8);
+  orca_service_.SetMemoryUtilization(0.4);
+  ReadResponses([](const OrcaLoadReport& response) {
+    EXPECT_EQ(response.cpu_utilization(), 0.8);
+    EXPECT_EQ(response.mem_utilization(), 0.4);
+    EXPECT_THAT(response.utilization(), ::testing::UnorderedElementsAre());
+  });
+  // Unset CPU and memory utilization and set a named utilization.
+  orca_service_.DeleteCpuUtilization();
+  orca_service_.DeleteMemoryUtilization();
+  orca_service_.SetNamedUtilization(kMetricName1, 0.3);
+  ReadResponses([&](const OrcaLoadReport& response) {
+    EXPECT_EQ(response.cpu_utilization(), 0);
+    EXPECT_EQ(response.mem_utilization(), 0);
+    EXPECT_THAT(
+        response.utilization(),
+        ::testing::UnorderedElementsAre(::testing::Pair(kMetricName1, 0.3)));
+  });
+  // Unset the previous named utilization and set two new ones.
+  orca_service_.DeleteNamedUtilization(kMetricName1);
+  orca_service_.SetNamedUtilization(kMetricName2, 0.2);
+  orca_service_.SetNamedUtilization(kMetricName3, 0.1);
+  ReadResponses([&](const OrcaLoadReport& response) {
+    EXPECT_EQ(response.cpu_utilization(), 0);
+    EXPECT_EQ(response.mem_utilization(), 0);
+    EXPECT_THAT(
+        response.utilization(),
+        ::testing::UnorderedElementsAre(::testing::Pair(kMetricName2, 0.2),
+                                        ::testing::Pair(kMetricName3, 0.1)));
+  });
+  // Replace the entire named metric map at once.
+  orca_service_.SetAllNamedUtilization(
+      {{kMetricName2, 0.5}, {kMetricName4, 0.9}});
+  ReadResponses([&](const OrcaLoadReport& response) {
+    EXPECT_EQ(response.cpu_utilization(), 0);
+    EXPECT_EQ(response.mem_utilization(), 0);
+    EXPECT_THAT(
+        response.utilization(),
+        ::testing::UnorderedElementsAre(::testing::Pair(kMetricName2, 0.5),
+                                        ::testing::Pair(kMetricName4, 0.9)));
+  });
+}
+
+}  // namespace
+}  // namespace testing
+}  // namespace grpc
+
+int main(int argc, char** argv) {
+  grpc::testing::TestEnvironment env(&argc, argv);
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}

tools/doxygen/Doxyfile.c++

@@ -947,6 +947,7 @@ include/grpcpp/create_channel.h \
 include/grpcpp/create_channel_binder.h \
 include/grpcpp/create_channel_posix.h \
 include/grpcpp/ext/health_check_service_server_builder_option.h \
+include/grpcpp/ext/orca_service.h \
 include/grpcpp/generic/async_generic_service.h \
 include/grpcpp/generic/generic_stub.h \
 include/grpcpp/grpcpp.h \

tools/doxygen/Doxyfile.c++.internal

@@ -947,6 +947,7 @@ include/grpcpp/create_channel.h \
 include/grpcpp/create_channel_binder.h \
 include/grpcpp/create_channel_posix.h \
 include/grpcpp/ext/health_check_service_server_builder_option.h \
+include/grpcpp/ext/orca_service.h \
 include/grpcpp/generic/async_generic_service.h \
 include/grpcpp/generic/generic_stub.h \
 include/grpcpp/grpcpp.h \
@@ -1550,6 +1551,8 @@ src/core/ext/upb-generated/xds/core/v3/resource_name.upb.c \
 src/core/ext/upb-generated/xds/core/v3/resource_name.upb.h \
 src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.c \
 src/core/ext/upb-generated/xds/data/orca/v3/orca_load_report.upb.h \
+src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.c \
+src/core/ext/upb-generated/xds/service/orca/v3/orca.upb.h \
 src/core/ext/upb-generated/xds/type/matcher/v3/matcher.upb.c \
 src/core/ext/upb-generated/xds/type/matcher/v3/matcher.upb.h \
 src/core/ext/upb-generated/xds/type/matcher/v3/regex.upb.c \
@@ -2526,6 +2529,7 @@ src/cpp/server/health/default_health_check_service.h \
 src/cpp/server/health/health_check_service.cc \
 src/cpp/server/health/health_check_service_server_builder_option.cc \
 src/cpp/server/insecure_server_credentials.cc \
+src/cpp/server/orca/orca_service.cc \
 src/cpp/server/secure_server_credentials.cc \
 src/cpp/server/secure_server_credentials.h \
 src/cpp/server/server_builder.cc \

tools/run_tests/generated/tests.json

@@ -5499,6 +5499,30 @@
     ],
     "uses_polling": false
   },
+  {
+    "args": [],
+    "benchmark": false,
+    "ci_platforms": [
+      "linux",
+      "mac",
+      "posix",
+      "windows"
+    ],
+    "cpu_cost": 1.0,
+    "exclude_configs": [],
+    "exclude_iomgrs": [],
+    "flaky": false,
+    "gtest": true,
+    "language": "c++",
+    "name": "orca_service_end2end_test",
+    "platforms": [
+      "linux",
+      "mac",
+      "posix",
+      "windows"
+    ],
+    "uses_polling": true
+  },
   {
     "args": [],
     "benchmark": false,