[#11205] Trivial RPC methods

Summary:
Currently, most of our RPC endpoints has a trivial implementation, which takes request, synchronously process, and sends the response.
But our generated service methods allow asynchronous processing, which complicates the writing of every method, even it doesn't require asynchronous processing.
This diff adds the ability to specify that method is trivial.
So his service virtual method will have signature:
```Result<ResponsePB> Method(const RequestPB& req, CoarseTimePoint deadline);```
instead of
```void Method(const RequestPB req, ResponsePB* resp, RpcContext context);```

Test Plan: ybd --gtest_filter RpcStubTest.Trivial

Reviewers: dmitry

Reviewed By: dmitry

Subscribers: ybase, bogdan

Differential Revision: https://phabricator.dev.yugabyte.com/D14990

Author: spolitov

build-support/common-build-env.sh

@@ -2231,6 +2231,7 @@ activate_virtualenv() {
     pip_no_cache="--no-cache-dir"
   fi
 
+  which pip3
   local pip_executable=pip3
   if ! "$yb_readonly_virtualenv"; then
     local requirements_file_path="$YB_SRC_ROOT/requirements_frozen.txt"

src/yb/gen_yrpc/metric_descriptor.cc

@@ -15,6 +15,8 @@
 
 #include <google/protobuf/descriptor.h>
 
+#include "yb/gen_yrpc/model.h"
+
 namespace yb {
 namespace gen_yrpc {
 
@@ -66,35 +68,45 @@ void GenerateMetricDefines(
   }
 }
 
-void GenerateHandlerAssignment(YBPrinter printer) {
+void GenerateHandlerAssignment(
+    YBPrinter printer, const google::protobuf::MethodDescriptor* method) {
   printer(".handler = [this](::yb::rpc::InboundCallPtr call) {\n");
   ScopedIndent handler_indent(printer);
   printer(
       "call->SetRpcMethodMetrics(methods_["
           "static_cast<size_t>($service_method_enum$::$metric_enum_key$)].metrics);\n"
       "::yb::rpc::HandleCall<::yb::rpc::$params$Impl<$request$, $response$>>(\n"
       "    std::move(call), [this](const $request$* req, $response$* resp, "
-          "::yb::rpc::RpcContext rpc_context) {\n"
-      "  $rpc_name$(req, resp, std::move(rpc_context));\n"
+          "::yb::rpc::RpcContext rpc_context) {\n");
+  if (IsTrivialMethod(method)) {
+    printer(
+        "  auto result = $rpc_name$(*req, rpc_context.GetClientDeadline());\n"
+        "  rpc_context.RespondTrivial(&result, resp);\n"
+    );
+  } else {
+    printer("  $rpc_name$(req, resp, std::move(rpc_context));\n");
+  }
+  printer(
       "});\n"
   );
   handler_indent.Reset("},\n");
 }
 
 void GenerateMethodAssignments(
     YBPrinter printer, const google::protobuf::ServiceDescriptor* service,
-    const std::string &mutable_metric_fmt, bool method,
+    const std::string &mutable_metric_fmt, bool service_side,
     const std::vector<MetricDescriptor>& metric_descriptors) {
   ScopedIndent indent(printer);
 
   for (int method_idx = 0; method_idx < service->method_count(); ++method_idx) {
-    ScopedSubstituter method_subs(printer, service->method(method_idx), rpc::RpcSides::SERVICE);
+    auto* method = service->method(method_idx);
+    ScopedSubstituter method_subs(printer, method, rpc::RpcSides::SERVICE);
 
     printer(mutable_metric_fmt + " = {\n");
-    if (method) {
+    if (service_side) {
       ScopedIndent method_indent(printer);
       printer(".method = ::yb::rpc::RemoteMethod(\"$full_service_name$\", \"$rpc_name$\"),\n");
-      GenerateHandlerAssignment(printer);
+      GenerateHandlerAssignment(printer, method);
       printer(".metrics = ::yb::rpc::RpcMethodMetrics(\n");
     }
     bool first = true;
@@ -105,13 +117,13 @@ void GenerateMethodAssignments(
         printer(",\n");
       }
       ScopedSubstituter metric_subs(printer, desc.CreateSubstitutions());
-      if (method) {
+      if (service_side) {
         printer("  ");
       }
       printer(
           "    METRIC_$metric_prefix$$metric_name$_$rpc_full_name_plainchars$.Instantiate(entity)");
     }
-    printer((method ? ")" : std::string()) + "\n};\n\n");
+    printer((service_side ? ")" : std::string()) + "\n};\n\n");
   }
 }
 

src/yb/gen_yrpc/metric_descriptor.h

@@ -41,7 +41,7 @@ void GenerateMetricDefines(
 
 void GenerateMethodAssignments(
     YBPrinter printer, const google::protobuf::ServiceDescriptor* service,
-    const std::string &mutable_metric_fmt, bool method,
+    const std::string &mutable_metric_fmt, bool service_side,
     const std::vector<MetricDescriptor>& metric_descriptors);
 
 } // namespace gen_yrpc

src/yb/gen_yrpc/model.cc

@@ -22,6 +22,8 @@
 #include "yb/gutil/strings/join.h"
 #include "yb/gutil/strings/split.h"
 
+#include "yb/rpc/service.pb.h"
+
 using google::protobuf::internal::WireFormatLite;
 
 namespace yb {
@@ -87,6 +89,10 @@ bool IsLightweightMethod(const google::protobuf::MethodDescriptor* method, rpc::
   return options.sides() == side || options.sides() == rpc::RpcSides::BOTH;
 }
 
+bool IsTrivialMethod(const google::protobuf::MethodDescriptor* method) {
+  return method->options().GetExtension(rpc::trivial);
+}
+
 bool HasLightweightMethod(const google::protobuf::ServiceDescriptor* service, rpc::RpcSides side) {
   for (int i = 0; i != service->method_count(); ++i) {
     if (IsLightweightMethod(service->method(i), side)) {

src/yb/gen_yrpc/model.h

@@ -34,6 +34,7 @@ google::protobuf::internal::WireFormatLite::WireType WireType(
 size_t FixedSize(const google::protobuf::FieldDescriptor* field);
 std::string MakeLightweightName(const std::string& input);
 bool IsLightweightMethod(const google::protobuf::MethodDescriptor* method, rpc::RpcSides side);
+bool IsTrivialMethod(const google::protobuf::MethodDescriptor* method);
 bool HasLightweightMethod(const google::protobuf::ServiceDescriptor* service, rpc::RpcSides side);
 bool HasLightweightMethod(const google::protobuf::FileDescriptor* file, rpc::RpcSides side);
 std::string ReplaceNamespaceDelimiters(const std::string& arg_full_name);

src/yb/gen_yrpc/service_generator.cc

@@ -74,6 +74,8 @@ void ServiceGenerator::Header(YBPrinter printer, const google::protobuf::FileDes
     "#include \"yb/rpc/rpc_header.pb.h\"\n"
     "#include \"yb/rpc/service_if.h\"\n"
     "\n"
+    "#include \"yb/util/monotime.h\"\n"
+    "\n"
     "namespace yb {\n"
     "class MetricEntity;\n"
     "} // namespace yb\n"
@@ -106,12 +108,19 @@ void ServiceGenerator::Header(YBPrinter printer, const google::protobuf::FileDes
       const auto* method = service->method(method_idx);
       ScopedSubstituter method_subs(printer, method, rpc::RpcSides::SERVICE);
 
-      printer(
-        "  virtual void $rpc_name$(\n"
-        "      const $request$ *req,\n"
-        "      $response$ *resp,\n"
-        "      ::yb::rpc::RpcContext context) = 0;\n"
-      );
+      if (IsTrivialMethod(method)) {
+        printer(
+          "  virtual ::yb::Result<$response$> $rpc_name$(\n"
+          "      const $request$& req, ::yb::CoarseTimePoint deadline) = 0;\n"
+        );
+      } else {
+        printer(
+          "  virtual void $rpc_name$(\n"
+          "      const $request$* req,\n"
+          "      $response$* resp,\n"
+          "      ::yb::rpc::RpcContext context) = 0;\n"
+        );
+      }
     }
 
     printer(
@@ -160,6 +169,40 @@ void ServiceGenerator::Source(YBPrinter printer, const google::protobuf::FileDes
 
   printer("$open_namespace$\n");
 
+  std::set<std::string> error_types;
+  for (int service_idx = 0; service_idx < file->service_count(); ++service_idx) {
+    const auto* service = file->service(service_idx);
+    for (int method_idx = 0; method_idx < service->method_count(); ++method_idx) {
+      auto* method = service->method(method_idx);
+      if (IsTrivialMethod(method)) {
+        Lightweight lightweight(IsLightweightMethod(method, rpc::RpcSides::SERVICE));
+        auto resp = method->output_type();
+        std::string type;
+        for (int field_idx = 0; field_idx < resp->field_count(); ++field_idx) {
+          auto* field = resp->field(field_idx);
+          if (field->name() == "error") {
+            type = MapFieldType(field, lightweight);
+            break;
+          } else if (field->name() == "status") {
+            type = MapFieldType(field, lightweight);
+            // We don't break here, since error has greater priority than status.
+          }
+        }
+        if (!type.empty()) {
+          error_types.insert(type);
+        }
+      }
+    }
+  }
+
+  if (!error_types.empty()) {
+    for (const auto& type : error_types) {
+      printer("void SetupError(" + type + "* error, const Status& status);\n");
+    }
+    printer("\n");
+  }
+
+
   for (int service_idx = 0; service_idx < file->service_count(); ++service_idx) {
     const auto* service = file->service(service_idx);
     ScopedSubstituter service_subs(printer, service);

src/yb/rpc/rpc-test-base.cc

@@ -380,6 +380,16 @@ class CalculatorService: public CalculatorServiceIf {
     context.RespondSuccess();
   }
 
+  Result<rpc_test::TrivialResponsePB> Trivial(
+      const rpc_test::TrivialRequestPB& req, CoarseTimePoint deadline) override {
+    if (req.value() < 0) {
+      return STATUS_FORMAT(InvalidArgument, "Negative value: $0", req.value());
+    }
+    rpc_test::TrivialResponsePB resp;
+    resp.set_value(req.value());
+    return resp;
+  }
+
  private:
   void DoSleep(const SleepRequestPB* req, RpcContext context) {
     SleepFor(MonoDelta::FromMicroseconds(req->sleep_micros()));
@@ -608,4 +618,13 @@ MessengerBuilder RpcTestBase::CreateMessengerBuilder(const string &name,
 }
 
 } // namespace rpc
+
+namespace rpc_test {
+
+void SetupError(TrivialErrorPB* error, const Status& status) {
+  error->set_code(status.code());
+}
+
+}
+
 } // namespace yb

src/yb/rpc/rpc_context.h

@@ -34,6 +34,8 @@
 
 #include <string>
 
+#include <boost/type_traits/is_detected.hpp>
+
 #include "yb/rpc/rpc_header.pb.h"
 #include "yb/rpc/serialization.h"
 #include "yb/rpc/service_if.h"
@@ -144,6 +146,33 @@ class RpcCallLWParamsImpl : public RpcCallLWParams {
   Resp resp_;
 };
 
+template <class T>
+using MutableErrorDetector = decltype(boost::declval<T&>().mutable_error());
+
+template <bool>
+struct ResponseErrorHelper;
+
+template <>
+struct ResponseErrorHelper<true> {
+  template <class T>
+  static auto Apply(T* t) {
+    return t->mutable_error();
+  }
+};
+
+template <>
+struct ResponseErrorHelper<false> {
+  template <class T>
+  static auto Apply(T* t) {
+    return t->mutable_status();
+  }
+};
+
+template <class T>
+auto ResponseError(T* t) {
+  return ResponseErrorHelper<boost::is_detected_v<MutableErrorDetector, T>>::Apply(t);
+}
+
 // The context provided to a generated ServiceIf. This provides
 // methods to respond to the RPC. In the future, this will also
 // include methods to access information about the caller: e.g
@@ -276,6 +305,17 @@ class RpcContext {
     return *params_;
   }
 
+  template <class Response>
+  void RespondTrivial(Result<Response>* result, Response* response) {
+    if (result->ok()) {
+      response->Swap(result->get_ptr());
+    } else {
+      SetupError(ResponseError(response), result->status());
+    }
+    RespondSuccess();
+  }
+
+
   // Panic the server. This logs a fatal error with the given message, and
   // also includes the current RPC request, requestor, trace information, etc,
   // to make it easier to debug.

src/yb/rpc/rpc_stub-test.cc

@@ -1037,5 +1037,25 @@ TEST_F(RpcStubTest, CustomServiceName) {
   ASSERT_EQ(resp.result(), "yugabyte");
 }
 
+TEST_F(RpcStubTest, Trivial) {
+  CalculatorServiceProxy proxy(proxy_cache_.get(), server_hostport_);
+
+  RpcController controller;
+  controller.set_timeout(30s);
+
+  rpc_test::TrivialRequestPB req;
+  req.set_value(42);
+  rpc_test::TrivialResponsePB resp;
+  ASSERT_OK(proxy.Trivial(req, &resp, &controller));
+  ASSERT_EQ(resp.value(), req.value());
+
+  req.set_value(-1);
+  controller.Reset();
+  controller.set_timeout(30s);
+  ASSERT_OK(proxy.Trivial(req, &resp, &controller));
+  ASSERT_TRUE(resp.has_error());
+  ASSERT_EQ(resp.error().code(), Status::Code::kInvalidArgument);
+}
+
 } // namespace rpc
 } // namespace yb

src/yb/rpc/rtest.proto

@@ -147,6 +147,10 @@ service CalculatorService {
   rpc Lightweight(LightweightRequestPB) returns (LightweightResponsePB) {
     option (yb.rpc.lightweight_method).sides = SERVICE;
   };
+
+  rpc Trivial(TrivialRequestPB) returns (TrivialResponsePB) {
+    option (yb.rpc.trivial) = true;
+  };
 }
 
 message ConcatRequestPB {
@@ -257,3 +261,16 @@ message LightweightResponsePB {
 
   optional string short_debug_string = 100;
 }
+
+message TrivialRequestPB {
+  optional int32 value = 1;
+}
+
+message TrivialErrorPB {
+  optional int32 code = 1;
+}
+
+message TrivialResponsePB {
+  optional TrivialErrorPB error = 1;
+  optional int32 value = 2;
+}

src/yb/rpc/service.proto

@@ -20,3 +20,7 @@ package yb.rpc;
 extend google.protobuf.ServiceOptions {
   string custom_service_name = 50011;
 }
+
+extend google.protobuf.MethodOptions {
+  bool trivial = 50001;
+}