test/cpp/qps/client_callback.cc - platform/external/grpc-grpc - Git at Google

 //
 //
 // Copyright 2015 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 <list>
 #include <memory>
 #include <mutex>
 #include <sstream>
 #include <string>
 #include <thread>
 #include <utility>
 #include <vector>

 #include "absl/memory/memory.h"

 #include <grpc/grpc.h>
 #include <grpc/support/cpu.h>
 #include <grpc/support/log.h>
 #include <grpcpp/alarm.h>
 #include <grpcpp/channel.h>
 #include <grpcpp/client_context.h>

 #include "src/core/lib/gprpp/crash.h"
 #include "src/proto/grpc/testing/benchmark_service.grpc.pb.h"
 #include "test/cpp/qps/client.h"
 #include "test/cpp/qps/usage_timer.h"

 namespace grpc {
 namespace testing {

 ///
 /// Maintains context info per RPC
 ///
 struct CallbackClientRpcContext {
   explicit CallbackClientRpcContext(BenchmarkService::Stub* stub)
       : alarm_(nullptr), stub_(stub) {}

   ~CallbackClientRpcContext() {}

   SimpleResponse response_;
   ClientContext context_;
   std::unique_ptr<Alarm> alarm_;
   BenchmarkService::Stub* stub_;
 };

 static std::unique_ptr<BenchmarkService::Stub> BenchmarkStubCreator(
     const std::shared_ptr<Channel>& ch) {
   return BenchmarkService::NewStub(ch);
 }

 class CallbackClient
     : public ClientImpl<BenchmarkService::Stub, SimpleRequest> {
  public:
   explicit CallbackClient(const ClientConfig& config)
       : ClientImpl<BenchmarkService::Stub, SimpleRequest>(
             config, BenchmarkStubCreator) {
     num_threads_ = NumThreads(config);
     rpcs_done_ = 0;

     //  Don't divide the fixed load among threads as the user threads
     //  only bootstrap the RPCs
     SetupLoadTest(config, 1);
     total_outstanding_rpcs_ =
         config.client_channels() * config.outstanding_rpcs_per_channel();
   }

   ~CallbackClient() override {}

   ///
   /// The main thread of the benchmark will be waiting on DestroyMultithreading.
   /// Increment the rpcs_done_ variable to signify that the Callback RPC
   /// after thread completion is done. When the last outstanding rpc increments
   /// the counter it should also signal the main thread's conditional variable.
   ///
   void NotifyMainThreadOfThreadCompletion() {
     std::lock_guard<std::mutex> l(shutdown_mu_);
     rpcs_done_++;
     if (rpcs_done_ == total_outstanding_rpcs_) {
       shutdown_cv_.notify_one();
     }
   }

   gpr_timespec NextRPCIssueTime() {
     std::lock_guard<std::mutex> l(next_issue_time_mu_);
     return Client::NextIssueTime(0);
   }

  protected:
   size_t num_threads_;
   size_t total_outstanding_rpcs_;
   // The below mutex and condition variable is used by main benchmark thread to
   // wait on completion of all RPCs before shutdown
   std::mutex shutdown_mu_;
   std::condition_variable shutdown_cv_;
   // Number of rpcs done after thread completion
   size_t rpcs_done_;
   // Vector of Context data pointers for running a RPC
   std::vector<std::unique_ptr<CallbackClientRpcContext>> ctx_;

   virtual void InitThreadFuncImpl(size_t thread_idx) = 0;
   virtual bool ThreadFuncImpl(Thread* t, size_t thread_idx) = 0;

   void ThreadFunc(size_t thread_idx, Thread* t) override {
     InitThreadFuncImpl(thread_idx);
     ThreadFuncImpl(t, thread_idx);
   }

  private:
   std::mutex next_issue_time_mu_;  // Used by next issue time

   int NumThreads(const ClientConfig& config) {
     int num_threads = config.async_client_threads();
     if (num_threads <= 0) {  // Use dynamic sizing
       num_threads = cores_;
       gpr_log(GPR_INFO, "Sizing callback client to %d threads", num_threads);
     }
     return num_threads;
   }

   ///
   /// Wait until all outstanding Callback RPCs are done
   ///
   void DestroyMultithreading() final {
     std::unique_lock<std::mutex> l(shutdown_mu_);
     while (rpcs_done_ != total_outstanding_rpcs_) {
       shutdown_cv_.wait(l);
     }
     EndThreads();
   }
 };

 class CallbackUnaryClient final : public CallbackClient {
  public:
   explicit CallbackUnaryClient(const ClientConfig& config)
       : CallbackClient(config) {
     for (int ch = 0; ch < config.client_channels(); ch++) {
       for (int i = 0; i < config.outstanding_rpcs_per_channel(); i++) {
         ctx_.emplace_back(
             new CallbackClientRpcContext(channels_[ch].get_stub()));
       }
     }
     StartThreads(num_threads_);
   }
   ~CallbackUnaryClient() override {}

  protected:
   bool ThreadFuncImpl(Thread* t, size_t thread_idx) override {
     for (size_t vector_idx = thread_idx; vector_idx < total_outstanding_rpcs_;
          vector_idx += num_threads_) {
       ScheduleRpc(t, vector_idx);
     }
     return true;
   }

   void InitThreadFuncImpl(size_t /*thread_idx*/) override {}

  private:
   void ScheduleRpc(Thread* t, size_t vector_idx) {
     if (!closed_loop_) {
       gpr_timespec next_issue_time = NextRPCIssueTime();
       // Start an alarm callback to run the internal callback after
       // next_issue_time
       if (ctx_[vector_idx]->alarm_ == nullptr) {
         ctx_[vector_idx]->alarm_ = std::make_unique<Alarm>();
       }
       ctx_[vector_idx]->alarm_->Set(next_issue_time,
                                     [this, t, vector_idx](bool /*ok*/) {
                                       IssueUnaryCallbackRpc(t, vector_idx);
                                     });
     } else {
       IssueUnaryCallbackRpc(t, vector_idx);
     }
   }

   void IssueUnaryCallbackRpc(Thread* t, size_t vector_idx) {
     double start = UsageTimer::Now();
     ctx_[vector_idx]->stub_->async()->UnaryCall(
         (&ctx_[vector_idx]->context_), &request_, &ctx_[vector_idx]->response_,
         [this, t, start, vector_idx](grpc::Status s) {
           // Update Histogram with data from the callback run
           HistogramEntry entry;
           if (s.ok()) {
             entry.set_value((UsageTimer::Now() - start) * 1e9);
           }
           entry.set_status(s.error_code());
           t->UpdateHistogram(&entry);

           if (ThreadCompleted() || !s.ok()) {
             // Notify thread of completion
             NotifyMainThreadOfThreadCompletion();
           } else {
             // Reallocate ctx for next RPC
             ctx_[vector_idx] = std::make_unique<CallbackClientRpcContext>(
                 ctx_[vector_idx]->stub_);
             // Schedule a new RPC
             ScheduleRpc(t, vector_idx);
           }
         });
   }
 };

 class CallbackStreamingClient : public CallbackClient {
  public:
   explicit CallbackStreamingClient(const ClientConfig& config)
       : CallbackClient(config),
         messages_per_stream_(config.messages_per_stream()) {
     for (int ch = 0; ch < config.client_channels(); ch++) {
       for (int i = 0; i < config.outstanding_rpcs_per_channel(); i++) {
         ctx_.emplace_back(
             new CallbackClientRpcContext(channels_[ch].get_stub()));
       }
     }
     StartThreads(num_threads_);
   }
   ~CallbackStreamingClient() override {}

   void AddHistogramEntry(double start, bool ok, Thread* thread_ptr) {
     // Update Histogram with data from the callback run
     HistogramEntry entry;
     if (ok) {
       entry.set_value((UsageTimer::Now() - start) * 1e9);
     }
     thread_ptr->UpdateHistogram(&entry);
   }

   int messages_per_stream() { return messages_per_stream_; }

  protected:
   const int messages_per_stream_;
 };

 class CallbackStreamingPingPongClient : public CallbackStreamingClient {
  public:
   explicit CallbackStreamingPingPongClient(const ClientConfig& config)
       : CallbackStreamingClient(config) {}
   ~CallbackStreamingPingPongClient() override {}
 };

 class CallbackStreamingPingPongReactor final
     : public grpc::ClientBidiReactor<SimpleRequest, SimpleResponse> {
  public:
   CallbackStreamingPingPongReactor(
       CallbackStreamingPingPongClient* client,
       std::unique_ptr<CallbackClientRpcContext> ctx)
       : client_(client), ctx_(std::move(ctx)), messages_issued_(0) {}

   void StartNewRpc() {
     ctx_->stub_->async()->StreamingCall(&(ctx_->context_), this);
     write_time_ = UsageTimer::Now();
     StartWrite(client_->request());
     writes_done_started_.clear();
     StartCall();
   }

   void OnWriteDone(bool ok) override {
     if (!ok) {
       gpr_log(GPR_ERROR, "Error writing RPC");
     }
     if ((!ok || client_->ThreadCompleted()) &&
         !writes_done_started_.test_and_set()) {
       StartWritesDone();
     }
     StartRead(&ctx_->response_);
   }

   void OnReadDone(bool ok) override {
     client_->AddHistogramEntry(write_time_, ok, thread_ptr_);

     if (client_->ThreadCompleted() || !ok ||
         (client_->messages_per_stream() != 0 &&
          ++messages_issued_ >= client_->messages_per_stream())) {
       if (!ok) {
         gpr_log(GPR_ERROR, "Error reading RPC");
       }
       if (!writes_done_started_.test_and_set()) {
         StartWritesDone();
       }
       return;
     }
     if (!client_->IsClosedLoop()) {
       gpr_timespec next_issue_time = client_->NextRPCIssueTime();
       // Start an alarm callback to run the internal callback after
       // next_issue_time
       ctx_->alarm_->Set(next_issue_time, [this](bool /*ok*/) {
         write_time_ = UsageTimer::Now();
         StartWrite(client_->request());
       });
     } else {
       write_time_ = UsageTimer::Now();
       StartWrite(client_->request());
     }
   }

   void OnDone(const Status& s) override {
     if (client_->ThreadCompleted() || !s.ok()) {
       client_->NotifyMainThreadOfThreadCompletion();
       return;
     }
     ctx_ = std::make_unique<CallbackClientRpcContext>(ctx_->stub_);
     ScheduleRpc();
   }

   void ScheduleRpc() {
     if (!client_->IsClosedLoop()) {
       gpr_timespec next_issue_time = client_->NextRPCIssueTime();
       // Start an alarm callback to run the internal callback after
       // next_issue_time
       if (ctx_->alarm_ == nullptr) {
         ctx_->alarm_ = std::make_unique<Alarm>();
       }
       ctx_->alarm_->Set(next_issue_time,
                         [this](bool /*ok*/) { StartNewRpc(); });
     } else {
       StartNewRpc();
     }
   }

   void set_thread_ptr(Client::Thread* ptr) { thread_ptr_ = ptr; }

   CallbackStreamingPingPongClient* client_;
   std::unique_ptr<CallbackClientRpcContext> ctx_;
   std::atomic_flag writes_done_started_;
   Client::Thread* thread_ptr_;  // Needed to update histogram entries
   double write_time_;           // Track ping-pong round start time
   int messages_issued_;         // Messages issued by this stream
 };

 class CallbackStreamingPingPongClientImpl final
     : public CallbackStreamingPingPongClient {
  public:
   explicit CallbackStreamingPingPongClientImpl(const ClientConfig& config)
       : CallbackStreamingPingPongClient(config) {
     for (size_t i = 0; i < total_outstanding_rpcs_; i++) {
       reactor_.emplace_back(
           new CallbackStreamingPingPongReactor(this, std::move(ctx_[i])));
     }
   }
   ~CallbackStreamingPingPongClientImpl() override {}

   bool ThreadFuncImpl(Client::Thread* t, size_t thread_idx) override {
     for (size_t vector_idx = thread_idx; vector_idx < total_outstanding_rpcs_;
          vector_idx += num_threads_) {
       reactor_[vector_idx]->set_thread_ptr(t);
       reactor_[vector_idx]->ScheduleRpc();
     }
     return true;
   }

   void InitThreadFuncImpl(size_t /*thread_idx*/) override {}

  private:
   std::vector<std::unique_ptr<CallbackStreamingPingPongReactor>> reactor_;
 };

 // TODO(mhaidry) : Implement Streaming from client, server and both ways

 std::unique_ptr<Client> CreateCallbackClient(const ClientConfig& config) {
   switch (config.rpc_type()) {
     case UNARY:
       return std::unique_ptr<Client>(new CallbackUnaryClient(config));
     case STREAMING:
       return std::unique_ptr<Client>(
           new CallbackStreamingPingPongClientImpl(config));
     case STREAMING_FROM_CLIENT:
     case STREAMING_FROM_SERVER:
     case STREAMING_BOTH_WAYS:
       grpc_core::Crash(
           "STREAMING_FROM_* scenarios are not supported by the callback "
           "API");
     default:
       grpc_core::Crash(absl::StrCat("Unknown RPC type: ", config.rpc_type()));
   }
 }

 }  // namespace testing
 }  // namespace grpc
	//
	//
	// Copyright 2015 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 <list>
	#include <memory>
	#include <mutex>
	#include <sstream>
	#include <string>
	#include <thread>
	#include <utility>
	#include <vector>

	#include "absl/memory/memory.h"

	#include <grpc/grpc.h>
	#include <grpc/support/cpu.h>
	#include <grpc/support/log.h>
	#include <grpcpp/alarm.h>
	#include <grpcpp/channel.h>
	#include <grpcpp/client_context.h>

	#include "src/core/lib/gprpp/crash.h"
	#include "src/proto/grpc/testing/benchmark_service.grpc.pb.h"
	#include "test/cpp/qps/client.h"
	#include "test/cpp/qps/usage_timer.h"

	namespace grpc {
	namespace testing {

	///
	/// Maintains context info per RPC
	///
	struct CallbackClientRpcContext {
	explicit CallbackClientRpcContext(BenchmarkService::Stub* stub)
	: alarm_(nullptr), stub_(stub) {}

	~CallbackClientRpcContext() {}

	SimpleResponse response_;
	ClientContext context_;
	std::unique_ptr<Alarm> alarm_;
	BenchmarkService::Stub* stub_;
	};

	static std::unique_ptr<BenchmarkService::Stub> BenchmarkStubCreator(
	const std::shared_ptr<Channel>& ch) {
	return BenchmarkService::NewStub(ch);
	}

	class CallbackClient
	: public ClientImpl<BenchmarkService::Stub, SimpleRequest> {
	public:
	explicit CallbackClient(const ClientConfig& config)
	: ClientImpl<BenchmarkService::Stub, SimpleRequest>(
	config, BenchmarkStubCreator) {
	num_threads_ = NumThreads(config);
	rpcs_done_ = 0;

	// Don't divide the fixed load among threads as the user threads
	// only bootstrap the RPCs
	SetupLoadTest(config, 1);
	total_outstanding_rpcs_ =
	config.client_channels() * config.outstanding_rpcs_per_channel();
	}

	~CallbackClient() override {}

	///
	/// The main thread of the benchmark will be waiting on DestroyMultithreading.
	/// Increment the rpcs_done_ variable to signify that the Callback RPC
	/// after thread completion is done. When the last outstanding rpc increments
	/// the counter it should also signal the main thread's conditional variable.
	///
	void NotifyMainThreadOfThreadCompletion() {
	std::lock_guard<std::mutex> l(shutdown_mu_);
	rpcs_done_++;
	if (rpcs_done_ == total_outstanding_rpcs_) {
	shutdown_cv_.notify_one();
	}
	}

	gpr_timespec NextRPCIssueTime() {
	std::lock_guard<std::mutex> l(next_issue_time_mu_);
	return Client::NextIssueTime(0);
	}

	protected:
	size_t num_threads_;
	size_t total_outstanding_rpcs_;
	// The below mutex and condition variable is used by main benchmark thread to
	// wait on completion of all RPCs before shutdown
	std::mutex shutdown_mu_;
	std::condition_variable shutdown_cv_;
	// Number of rpcs done after thread completion
	size_t rpcs_done_;
	// Vector of Context data pointers for running a RPC
	std::vector<std::unique_ptr<CallbackClientRpcContext>> ctx_;

	virtual void InitThreadFuncImpl(size_t thread_idx) = 0;
	virtual bool ThreadFuncImpl(Thread* t, size_t thread_idx) = 0;

	void ThreadFunc(size_t thread_idx, Thread* t) override {
	InitThreadFuncImpl(thread_idx);
	ThreadFuncImpl(t, thread_idx);
	}

	private:
	std::mutex next_issue_time_mu_; // Used by next issue time

	int NumThreads(const ClientConfig& config) {
	int num_threads = config.async_client_threads();
	if (num_threads <= 0) { // Use dynamic sizing
	num_threads = cores_;
	gpr_log(GPR_INFO, "Sizing callback client to %d threads", num_threads);
	}
	return num_threads;
	}

	///
	/// Wait until all outstanding Callback RPCs are done
	///
	void DestroyMultithreading() final {
	std::unique_lock<std::mutex> l(shutdown_mu_);
	while (rpcs_done_ != total_outstanding_rpcs_) {
	shutdown_cv_.wait(l);
	}
	EndThreads();
	}
	};

	class CallbackUnaryClient final : public CallbackClient {
	public:
	explicit CallbackUnaryClient(const ClientConfig& config)
	: CallbackClient(config) {
	for (int ch = 0; ch < config.client_channels(); ch++) {
	for (int i = 0; i < config.outstanding_rpcs_per_channel(); i++) {
	ctx_.emplace_back(
	new CallbackClientRpcContext(channels_[ch].get_stub()));
	}
	}
	StartThreads(num_threads_);
	}
	~CallbackUnaryClient() override {}

	protected:
	bool ThreadFuncImpl(Thread* t, size_t thread_idx) override {
	for (size_t vector_idx = thread_idx; vector_idx < total_outstanding_rpcs_;
	vector_idx += num_threads_) {
	ScheduleRpc(t, vector_idx);
	}
	return true;
	}

	void InitThreadFuncImpl(size_t /thread_idx/) override {}

	private:
	void ScheduleRpc(Thread* t, size_t vector_idx) {
	if (!closed_loop_) {
	gpr_timespec next_issue_time = NextRPCIssueTime();
	// Start an alarm callback to run the internal callback after
	// next_issue_time
	if (ctx_[vector_idx]->alarm_ == nullptr) {
	ctx_[vector_idx]->alarm_ = std::make_unique<Alarm>();
	}
	ctx_[vector_idx]->alarm_->Set(next_issue_time,
	[this, t, vector_idx](bool /ok/) {
	IssueUnaryCallbackRpc(t, vector_idx);
	});
	} else {
	IssueUnaryCallbackRpc(t, vector_idx);
	}
	}

	void IssueUnaryCallbackRpc(Thread* t, size_t vector_idx) {
	double start = UsageTimer::Now();
	ctx_[vector_idx]->stub_->async()->UnaryCall(
	(&ctx_[vector_idx]->context_), &request_, &ctx_[vector_idx]->response_,
	[this, t, start, vector_idx](grpc::Status s) {
	// Update Histogram with data from the callback run
	HistogramEntry entry;
	if (s.ok()) {
	entry.set_value((UsageTimer::Now() - start) * 1e9);
	}
	entry.set_status(s.error_code());
	t->UpdateHistogram(&entry);

	if (ThreadCompleted() \|\| !s.ok()) {
	// Notify thread of completion
	NotifyMainThreadOfThreadCompletion();
	} else {
	// Reallocate ctx for next RPC
	ctx_[vector_idx] = std::make_unique<CallbackClientRpcContext>(
	ctx_[vector_idx]->stub_);
	// Schedule a new RPC
	ScheduleRpc(t, vector_idx);
	}
	});
	}
	};

	class CallbackStreamingClient : public CallbackClient {
	public:
	explicit CallbackStreamingClient(const ClientConfig& config)
	: CallbackClient(config),
	messages_per_stream_(config.messages_per_stream()) {
	for (int ch = 0; ch < config.client_channels(); ch++) {
	for (int i = 0; i < config.outstanding_rpcs_per_channel(); i++) {
	ctx_.emplace_back(
	new CallbackClientRpcContext(channels_[ch].get_stub()));
	}
	}
	StartThreads(num_threads_);
	}
	~CallbackStreamingClient() override {}

	void AddHistogramEntry(double start, bool ok, Thread* thread_ptr) {
	// Update Histogram with data from the callback run
	HistogramEntry entry;
	if (ok) {
	entry.set_value((UsageTimer::Now() - start) * 1e9);
	}
	thread_ptr->UpdateHistogram(&entry);
	}

	int messages_per_stream() { return messages_per_stream_; }

	protected:
	const int messages_per_stream_;
	};

	class CallbackStreamingPingPongClient : public CallbackStreamingClient {
	public:
	explicit CallbackStreamingPingPongClient(const ClientConfig& config)
	: CallbackStreamingClient(config) {}
	~CallbackStreamingPingPongClient() override {}
	};

	class CallbackStreamingPingPongReactor final
	: public grpc::ClientBidiReactor<SimpleRequest, SimpleResponse> {
	public:
	CallbackStreamingPingPongReactor(
	CallbackStreamingPingPongClient* client,
	std::unique_ptr<CallbackClientRpcContext> ctx)
	: client_(client), ctx_(std::move(ctx)), messages_issued_(0) {}

	void StartNewRpc() {
	ctx_->stub_->async()->StreamingCall(&(ctx_->context_), this);
	write_time_ = UsageTimer::Now();
	StartWrite(client_->request());
	writes_done_started_.clear();
	StartCall();
	}

	void OnWriteDone(bool ok) override {
	if (!ok) {
	gpr_log(GPR_ERROR, "Error writing RPC");
	}
	if ((!ok \|\| client_->ThreadCompleted()) &&
	!writes_done_started_.test_and_set()) {
	StartWritesDone();
	}
	StartRead(&ctx_->response_);
	}

	void OnReadDone(bool ok) override {
	client_->AddHistogramEntry(write_time_, ok, thread_ptr_);

	if (client_->ThreadCompleted() \|\| !ok \|\|
	(client_->messages_per_stream() != 0 &&
	++messages_issued_ >= client_->messages_per_stream())) {
	if (!ok) {
	gpr_log(GPR_ERROR, "Error reading RPC");
	}
	if (!writes_done_started_.test_and_set()) {
	StartWritesDone();
	}
	return;
	}
	if (!client_->IsClosedLoop()) {
	gpr_timespec next_issue_time = client_->NextRPCIssueTime();
	// Start an alarm callback to run the internal callback after
	// next_issue_time
	ctx_->alarm_->Set(next_issue_time, [this](bool /ok/) {
	write_time_ = UsageTimer::Now();
	StartWrite(client_->request());
	});
	} else {
	write_time_ = UsageTimer::Now();
	StartWrite(client_->request());
	}
	}

	void OnDone(const Status& s) override {
	if (client_->ThreadCompleted() \|\| !s.ok()) {
	client_->NotifyMainThreadOfThreadCompletion();
	return;
	}
	ctx_ = std::make_unique<CallbackClientRpcContext>(ctx_->stub_);
	ScheduleRpc();
	}

	void ScheduleRpc() {
	if (!client_->IsClosedLoop()) {
	gpr_timespec next_issue_time = client_->NextRPCIssueTime();
	// Start an alarm callback to run the internal callback after
	// next_issue_time
	if (ctx_->alarm_ == nullptr) {
	ctx_->alarm_ = std::make_unique<Alarm>();
	}
	ctx_->alarm_->Set(next_issue_time,
	[this](bool /ok/) { StartNewRpc(); });
	} else {
	StartNewRpc();
	}
	}

	void set_thread_ptr(Client::Thread* ptr) { thread_ptr_ = ptr; }

	CallbackStreamingPingPongClient* client_;
	std::unique_ptr<CallbackClientRpcContext> ctx_;
	std::atomic_flag writes_done_started_;
	Client::Thread* thread_ptr_; // Needed to update histogram entries
	double write_time_; // Track ping-pong round start time
	int messages_issued_; // Messages issued by this stream
	};

	class CallbackStreamingPingPongClientImpl final
	: public CallbackStreamingPingPongClient {
	public:
	explicit CallbackStreamingPingPongClientImpl(const ClientConfig& config)
	: CallbackStreamingPingPongClient(config) {
	for (size_t i = 0; i < total_outstanding_rpcs_; i++) {
	reactor_.emplace_back(
	new CallbackStreamingPingPongReactor(this, std::move(ctx_[i])));
	}
	}
	~CallbackStreamingPingPongClientImpl() override {}

	bool ThreadFuncImpl(Client::Thread* t, size_t thread_idx) override {
	for (size_t vector_idx = thread_idx; vector_idx < total_outstanding_rpcs_;
	vector_idx += num_threads_) {
	reactor_[vector_idx]->set_thread_ptr(t);
	reactor_[vector_idx]->ScheduleRpc();
	}
	return true;
	}

	void InitThreadFuncImpl(size_t /thread_idx/) override {}

	private:
	std::vector<std::unique_ptr<CallbackStreamingPingPongReactor>> reactor_;
	};

	// TODO(mhaidry) : Implement Streaming from client, server and both ways

	std::unique_ptr<Client> CreateCallbackClient(const ClientConfig& config) {
	switch (config.rpc_type()) {
	case UNARY:
	return std::unique_ptr<Client>(new CallbackUnaryClient(config));
	case STREAMING:
	return std::unique_ptr<Client>(
	new CallbackStreamingPingPongClientImpl(config));
	case STREAMING_FROM_CLIENT:
	case STREAMING_FROM_SERVER:
	case STREAMING_BOTH_WAYS:
	grpc_core::Crash(
	"STREAMING_FROM_* scenarios are not supported by the callback "
	"API");
	default:
	grpc_core::Crash(absl::StrCat("Unknown RPC type: ", config.rpc_type()));
	}
	}

	} // namespace testing
	} // namespace grpc