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December 23, 2020 15:04
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gRPC C++ async api wrapper
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#pragma once | |
#include <thread> | |
#include <google/protobuf/message.h> | |
#include <grpcpp/grpcpp.h> | |
#include <grpcpp/alarm.h> | |
#include <logger.h> | |
namespace grpcasyncservice | |
{ | |
using OnCreate = std::function<void(grpc::ServerContext *, | |
google::protobuf::Message *, | |
grpc::internal::ServerAsyncStreamingInterface *, | |
std::shared_ptr<grpc::CompletionQueue>, | |
std::shared_ptr<grpc::ServerCompletionQueue>, | |
void *)>; | |
using OnWork = std::function<bool(grpc::ServerContext &, | |
google::protobuf::Message *, | |
grpc::internal::ServerAsyncStreamingInterface *, | |
void *)>; | |
using FactoryFunction = std::function<std::shared_ptr<google::protobuf::Message>()>; | |
using Cache = std::list<std::shared_ptr<google::protobuf::Message>>; | |
struct Method | |
{ | |
Method(size_t cacheSize, | |
FactoryFunction requestFunc, | |
OnCreate _onCreate, | |
OnWork _onWork) | |
: onCreate(std::move(_onCreate)), onWork(std::move(_onWork)) | |
{ | |
for (size_t i = 0; i < cacheSize; ++i) | |
{ | |
cache.push_back(requestFunc()); | |
} | |
} | |
OnCreate onCreate; | |
OnWork onWork; | |
Cache cache; | |
std::shared_mutex lock; | |
}; | |
class InvokeTag | |
{ | |
public: | |
InvokeTag(std::shared_ptr<grpc::ServerCompletionQueue> _cq, Method &_method) | |
: cq(_cq), method(_method), state(State::CREATE), responder(&context) | |
{ | |
} | |
void invoke() | |
{ | |
switch (state) | |
{ | |
case State::CREATE: | |
{ | |
if (method.cache.empty()) | |
{ | |
grpc::Alarm alarm; | |
alarm.Set(cq.get(), | |
std::chrono::system_clock::now() + std::chrono::milliseconds(100), this); | |
} | |
else | |
{ | |
state = State::WORK; | |
{ | |
std::unique_lock lock(method.lock); | |
request = method.cache.front(); | |
method.cache.pop_front(); | |
} | |
method.onCreate(&context, request.get(), &responder, cq, cq, this); | |
} | |
break; | |
} | |
case State::WORK: | |
{ | |
std::call_once(flag, [_cq = cq, _method = std::ref(method)]() { | |
(new InvokeTag(_cq, _method))->invoke(); | |
}); | |
if (method.onWork(context, request.get(), &responder, this)) | |
{ | |
state = State::FINISH; | |
} | |
break; | |
} | |
case State::FINISH: | |
{ | |
request->Clear(); | |
{ | |
std::unique_lock lock(method.lock); | |
method.cache.push_back(request); | |
} | |
delete this; | |
break; | |
} | |
} | |
} | |
private: | |
enum class State | |
{ | |
CREATE, | |
WORK, | |
FINISH, | |
}; | |
private: | |
grpc::ServerContext context; | |
std::once_flag flag; | |
std::shared_ptr<grpc::ServerCompletionQueue> cq; | |
Method &method; | |
State state; | |
grpc::ServerAsyncWriter<google::protobuf::Message> responder; | |
std::shared_ptr<google::protobuf::Message> request; | |
}; | |
class ServiceImpl | |
{ | |
public: | |
ServiceImpl(std::shared_ptr<grpc::ServerCompletionQueue> _cq, | |
std::vector<std::shared_ptr<Method>> &methods) | |
: cq(_cq) | |
{ | |
for (auto &method: methods) | |
{ | |
(new InvokeTag(cq, *method))->invoke(); | |
} | |
} | |
void start() | |
{ | |
void *tag = nullptr; | |
bool ok = false; | |
while (cq->Next(&tag, &ok)) | |
{ | |
if (ok) | |
{ | |
static_cast<InvokeTag *>(tag)->invoke(); | |
} | |
} | |
} | |
private: | |
std::shared_ptr<grpc::ServerCompletionQueue> cq; | |
}; | |
class AsyncServiceImpl final | |
{ | |
public: | |
AsyncServiceImpl(size_t _threadsCount, grpc::ServerBuilder &_builder) | |
: threadsCount(_threadsCount), builder(_builder) | |
{ | |
} | |
template<typename Request> | |
AsyncServiceImpl ®isterMethod(size_t cacheSize, OnCreate onCreate, OnWork onWork) | |
{ | |
methods.push_back(std::make_shared<Method>( | |
cacheSize, []() { return std::make_shared<Request>(); }, std::move(onCreate), | |
std::move(onWork))); | |
return *this; | |
} | |
AsyncServiceImpl &start() | |
{ | |
for (size_t i = 0; i < threadsCount; ++i) | |
{ | |
queues.push_back(builder.AddCompletionQueue()); | |
} | |
server = builder.BuildAndStart(); | |
for (auto cq: queues) | |
{ | |
threads.emplace_back([this, cq]() { ServiceImpl(cq, methods).start(); }); | |
} | |
return *this; | |
} | |
void stop() | |
{ | |
server->Shutdown(); | |
for (auto &cq: queues) | |
{ | |
cq->Shutdown(); | |
} | |
} | |
void wait() | |
{ | |
for (auto &thr: threads) | |
{ | |
thr.join(); | |
} | |
} | |
private: | |
size_t threadsCount; | |
grpc::ServerBuilder &builder; | |
std::unique_ptr<grpc::Server> server; | |
std::vector<std::thread> threads; | |
std::vector<std::shared_ptr<Method>> methods; | |
std::vector<std::shared_ptr<grpc::ServerCompletionQueue>> queues; | |
}; | |
} // namespace grpcasyncservice |
Мы по итогу заменили аллокатор на другой, а саму асинхронную версию использовали потому что думали что в ней не будет проблемы с постоянным созданием новых потоков. Только после того как залезли в код gRPC, поняли что простое использование асинхронного АПИ не решит нашу проблему. Так как синхронный и асинхронный сервера используют один и тот же код для управления потоками из класса ThreadManager.
За примеры спасибо!
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Тоже игрался с grpc: https://github.com/aliakseis/grpc-demo
Не очень понял, а как вы в результате пофиксили проблему с аллокатором?