/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.

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 <memory>
#include <string>
#include <vector>

#include "tensorflow/core/distributed_runtime/rpc/grpc_state.h"
#include "tensorflow/core/distributed_runtime/rpc/grpc_util.h"
#include "tensorflow/core/framework/op_kernel.h"
#include "tensorflow/core/framework/tensor_types.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/refcount.h"
#include "tensorflow/core/util/rpc/call_container.h"
#include "tensorflow/core/util/rpc/rpc_factory.h"

#include "tensorflow/core/distributed_runtime/rpc/grpc_rpc_factory.h"

namespace tensorflow {

namespace internal {
class GrpcCall {
 public:
  explicit GrpcCall(CallContainer<GrpcCall>* container, int index, bool try_rpc,
                    const tstring* request_msg, tstring* response_msg,
                    int32* status_code, tstring* status_message)
      : container_(container),
        index_(index),
        try_rpc_(try_rpc),
        request_msg_(request_msg),
        response_msg_(response_msg),
        status_code_(status_code),
        status_message_(status_message) {}

  void StartCancel() { call_opts_.StartCancel(); }

  void Done(const Status& s) {
    DCHECK(container_ != nullptr);
    if (!s.ok() && try_rpc_) {
      DCHECK(status_code_ != nullptr);
      DCHECK(status_message_ != nullptr);
      *status_code_ = s.code();
      *status_message_ = s.error_message();
    }
    container_->Done(s, index_);
  }

  CallOptions* call_opts() { return &call_opts_; }
  int index() { return index_; }
  const tstring& request() const { return *request_msg_; }
  tstring* response() const { return response_msg_; }

 private:
  CallContainer<GrpcCall>* const container_;
  const int index_;
  bool try_rpc_;
  CallOptions call_opts_;
  const tstring* request_msg_;
  tstring* response_msg_;
  int* status_code_;
  tstring* status_message_;
};

}  // namespace internal

using internal::GrpcCall;

GrpcRPCFactory::GrpcRPCFactory(OpKernelConstruction* ctx, bool fail_fast,
                               int64 timeout_in_ms)
    : RPCFactory(), fail_fast_(fail_fast), timeout_in_ms_(timeout_in_ms) {
  // TODO(ebrevdo): Investigate possible performance improvements by
  // replacing this thread with a threadpool.
  polling_thread_ =
      ctx->env()->StartThread(ThreadOptions(), "rpc_op_grpc_factory", [this]() {
        void* tag;
        bool ok;
        while (completion_queue_.Next(&tag, &ok)) {
          GrpcClientCQTag* callback_tag = static_cast<GrpcClientCQTag*>(tag);
          callback_tag->OnCompleted(ok);
        }
      });
}

GrpcRPCFactory::~GrpcRPCFactory() {
  // The amount of time we wait depends on several parameters, including:
  //   - the value of the fail_fast attribute.
  //   - the timeout option of the rpc call in the proto declaration.
  //   - the network roundtrip time and service's execution time.
  //
  // If a connection is made but the service doesn't ever respond, and
  // there is no timeout option set for this rpc call, then it is
  // possible the RPC request will wait forever.
  //
  completion_queue_.Shutdown();
  delete polling_thread_;
}

void GrpcRPCFactory::Call(OpKernelContext* ctx, int64 num_elements,
                          const Tensor& address_t, const Tensor& method_t,
                          const Tensor& request_t, const bool try_rpc,
                          Tensor* response_t, Tensor* status_code_t,
                          Tensor* status_message_t,
                          AsyncOpKernel::DoneCallback done) {
  if (try_rpc) {
    // In this case status_code will never be set in the response,
    // so we just set it to OK.
    DCHECK(status_code_t != nullptr);
    status_code_t->flat<int32>().setConstant(
        static_cast<int>(errors::Code::OK));
  }

  CallContainer<GrpcCall>::CreateCallFn create_call_fn =
      [this, &request_t, &try_rpc, response_t, status_code_t, status_message_t](
          CallContainer<GrpcCall>* container, int index) {
        CreateCall(request_t, try_rpc, index, container, response_t,
                   status_code_t, status_message_t);
      };

  CallContainer<GrpcCall>::StartCallFn start_call_fn =
      [this, &address_t, &method_t](GrpcCall* call) {
        StartCall(address_t, method_t, call);
      };

  // This object will delete itself when done.
  new CallContainer<GrpcCall>(ctx, num_elements, fail_fast_, try_rpc,
                              std::move(done), std::move(create_call_fn),
                              std::move(start_call_fn));
}

::grpc::GenericStub* GrpcRPCFactory::GetOrCreateStubForAddress(
    const string& address) {
  mutex_lock lock(mu_);

  auto stub = stubs_.find(address);
  if (stub != stubs_.end()) return stub->second.get();

  ChannelPtr channel = CreateChannelForAddress(address);
  auto* created = new ::grpc::GenericStub(channel);
  stubs_[address].reset(created);
  return created;
}

GrpcRPCFactory::ChannelPtr GrpcRPCFactory::CreateChannelForAddress(
    const string& address) {
  ::grpc::ChannelArguments args;
  args.SetInt(GRPC_ARG_MAX_MESSAGE_LENGTH, std::numeric_limits<int32>::max());

  // Set a standard backoff timeout of 1s instead of the
  // (sometimes default) 20s.
  args.SetInt(GRPC_ARG_MAX_RECONNECT_BACKOFF_MS, 1000);
  return ::grpc::CreateCustomChannel(
      /*target=*/address, ::grpc::InsecureChannelCredentials(), args);
}

void GrpcRPCFactory::CreateCall(const Tensor& request_t, const bool try_rpc,
                                int index, CallContainer<GrpcCall>* container,
                                Tensor* response_t, Tensor* status_code_t,
                                Tensor* status_message_t) {
  auto request = request_t.flat<tstring>();
  auto get_request_ptr = [&request](int64 ix) -> const tstring* {
    return (request.size() > 1) ? &(request(ix)) : &(request(0));
  };
  auto response = response_t->flat<tstring>();
  int32* status_code_ptr = nullptr;
  tstring* status_message_ptr = nullptr;
  if (try_rpc) {
    status_code_ptr = status_code_t->flat<int32>().data();
    status_message_ptr = status_message_t->flat<tstring>().data();
  }
  container->RegisterCall(container, index, try_rpc, get_request_ptr(index),
                          &response(index),
                          (try_rpc) ? &status_code_ptr[index] : nullptr,
                          (try_rpc) ? &status_message_ptr[index] : nullptr);
}

void GrpcRPCFactory::StartCall(const Tensor& address_t, const Tensor& method_t,
                               GrpcCall* call) {
  auto address = address_t.flat<tstring>();
  auto method = method_t.flat<tstring>();
  // Stubs are maintained by the GrpcRPCFactory class and will be
  // deleted when the class is destroyed.
  ::grpc::GenericStub* singleton_stub = nullptr;
  if (address.size() == 1) {
    singleton_stub = GetOrCreateStubForAddress(address(0));
  }
  auto get_stub = [&address, this,
                   singleton_stub](int64 ix) -> ::grpc::GenericStub* {
    return (address.size() > 1) ? GetOrCreateStubForAddress(address(ix))
                                : singleton_stub;
  };
  auto get_method_ptr = [&method](int64 ix) -> const tstring* {
    return (method.size() > 1) ? &(method(ix)) : &(method(0));
  };

  int index = call->index();
  // This object will delete itself when done.
  new RPCState<tstring>(
      get_stub(index), &completion_queue_, *get_method_ptr(index),
      call->request(), call->response(),
      /*done=*/[call](const Status& s) { call->Done(s); }, call->call_opts(),
      /*threadpool=*/nullptr, fail_fast_, timeout_in_ms_, /*max_retries=*/0,
      /*target=*/nullptr);
}

}  // namespace tensorflow
