【gRPC】C++异步服务端优化版，多服务接口样例
官方的C++异步服务端API样例可读性并不好，理解起来非常的费劲，各种状态机也并不明了，整个运行过程也容易读不懂，因此此处参考网上的博客进行了重写，以求顺利读懂。
C++异步服务端实例，详细注释版
gRPC使用C++实现异步服务端的基本逻辑：
- 构建数据结构来存储需要处理的请求及其上下文信息，此处使用HandlerContext，相当于对到达的请求的封装
- 首先注册各个接口的HandlerContext，放入完成队列CompletionQueue中，当请求到达时，根据类型封装进对应的HandlerContext，由于是异步客户端，需要保证后面到达的请求也有HandlerContext用，所以用一个就要再创建一个空的放回去
- 运行完的接口，其HandlerContext需要销毁
以下代码的关键为run()方法中的逻辑以及HandlerContext的设置，每一步都有注释，可以详细观看
//官方样例的异步服务代码可读性太差了，状态机绕来绕去不直观，在这里参考网上的博客进行重写，类名随意
class AsyncTestServiceImplNew final
{
private:
// 当前服务器的地址
std::string server_address_;
// 当前服务器的完成队列
std::unique_ptr<ServerCompletionQueue> cq_;
// 当前服务器的异步服务
TestService::AsyncService service_;
// 服务器实例
std::unique_ptr<Server> server_;
struct HandlerContextBase
{
int type_; //请求的接口是哪个，1表示http，2表示download，3表示upload，后续有需要可以再添加
int status_; //当前处理状态，1表示处理请求构建响应，2表示发送响应
ServerContext ctx_; // rpc服务的上下文信息
};
//请求的上下文结构
template <typename RequestType, typename ResponseType>
struct HandlerContext : public HandlerContextBase
{
RequestType req_; //请求数据类型
ResponseType resp_; //响应数据类型
ServerAsyncResponseWriter<ResponseType> responder_; //响应器
HandlerContext() : responder_(&ctx_) {} //构造方法
};
// 定义好各个接口的上下文
typedef HandlerContext<HttpRequest, HttpResponse> HandlerHttpContext;
typedef HandlerContext<DownloadRequest, DownloadResponse> HandlerDownloadContext;
typedef HandlerContext<UploadRequest, UploadResponse> HandlerUploadContext;
public:
~AsyncTestServiceImplNew()
{
server_->Shutdown();
// 关闭服务器后也要关闭完成队列
cq_->Shutdown();
}
//构造时传入IP:Port即可
AsyncTestServiceImplNew(std::string server_address) : server_address_(server_address) {}
// 服务器与队列的关闭放入了析构函数中
void Run()
{
// std::string server_address = "localhost:50052";
// 服务器构建器
ServerBuilder builder;
// 服务器IP与端口指定，第二个参数表示该通道不经过身份验证
builder.AddListeningPort(server_address_, grpc::InsecureServerCredentials());
// 注册服务
builder.RegisterService(&service_);
// 为当前服务器创建完成队列
cq_ = builder.AddCompletionQueue();
// 构建并启动服务器
server_ = builder.BuildAndStart();
std::cout << "AysncTestServer_New is listening on " << server_address_ << std::endl;
// 为各个接口创建请求上下文，然后注册请求到服务端
HandlerHttpContext *http_context = new HandlerHttpContext;
http_context->type_ = 1;
http_context->status_ = 1;
HandlerDownloadContext *download_context = new HandlerDownloadContext;
download_context->type_ = 2;
download_context->status_ = 1;
HandlerUploadContext *upload_context = new HandlerUploadContext;
upload_context->type_ = 3;
upload_context->status_ = 1;
// 注册服务,参数从前到后分别是：rpc服务上下文，rpc请求对象，异步响应器，新的rpc请求使用的完成队列，通知完成使用的完成队列，唯一标识tag标识当前这次请求的上下文
service_.Requesthttp(&http_context->ctx_, &http_context->req_, &http_context->responder_, cq_.get(), cq_.get(), http_context);
service_.Requestdownload(&download_context->ctx_, &download_context->req_, &download_context->responder_, cq_.get(), cq_.get(), download_context);
service_.Requestupload(&upload_context->ctx_, &upload_context->req_, &upload_context->responder_, cq_.get(), cq_.get(), upload_context);
//创建线程池，用于运行请求的接口
ThreadPool pool(THREAD_POOL_SIZE);//THTREAD_POOL_SIZE自行定义
//不断从完成队列中取出请求，这里的请求都是在上面注册过的
while (true)
{
HandlerContextBase *handler_context = nullptr;
bool ok = false;
GPR_ASSERT(cq_->Next((void **)&handler_context, &ok));
GPR_ASSERT(ok);
//请求接口的类型，1是http，2是download，3是upload
int type = handler_context->type_;
//根据状态分别处理，1表示要进行接口调用，2表示已经完成，可以销毁该请求上下文了
if (handler_context->status_ == 2)
{
switch (type)
{
case 1:
delete (HandlerHttpContext *)handler_context;
break;
case 2:
delete (HandlerDownloadContext *)handler_context;
break;
case 3:
delete (HandlerUploadContext *)handler_context;
break;
}
continue;
}
//从完成队列中取出来了一个请求上下文来处理当前请求，就需要再放回去一个给后续到达的请求用
switch (type)
{
case 1:
{
HandlerHttpContext *http_context = new HandlerHttpContext;
http_context->type_ = 1;
http_context->status_ = 1;
// 注册服务,参数从前到后分别是：rpc服务上下文，rpc请求对象，异步响应器，新的rpc请求使用的完成队列，通知完成使用的完成队列，唯一标识tag标识当前这次请求的上下文
service_.Requesthttp(&http_context->ctx_, &http_context->req_, &http_context->responder_, cq_.get(), cq_.get(), http_context);
}
break;
case 2:
{
HandlerDownloadContext *download_context = new HandlerDownloadContext;
download_context->type_ = 2;
download_context->status_ = 1;
service_.Requestdownload(&download_context->ctx_, &download_context->req_, &download_context->responder_, cq_.get(), cq_.get(), download_context);
}
break;
case 3:
{
HandlerUploadContext *upload_context = new HandlerUploadContext;
upload_context->type_ = 3;
upload_context->status_ = 1;
service_.Requestupload(&upload_context->ctx_, &upload_context->req_, &upload_context->responder_, cq_.get(), cq_.get(), upload_context);
}
break;
}
//当前请求上下文的任务进行执行，放入线程池中去运行
pool.enqueue([type, handler_context, this]()
{
switch (type)
{
case 1:
{
HandlerHttpContext *h = (HandlerHttpContext *)handler_context;
Status status = http(&h->ctx_, &h->req_, &h->resp_);
h->status_ = 2; //设置状态为完成接口调用，准备进行响应
//调用responder_进行异步的响应发送，三个参数分别为发送的响应、状态码、请求处理在服务端的唯一tag
h->responder_.Finish(h->resp_, status, handler_context);
}
break;
case 2:
{
HandlerDownloadContext *h = (HandlerDownloadContext *)handler_context;
Status status = download(&h->ctx_, &h->req_, &h->resp_);
h->status_ = 2;
h->responder_.Finish(h->resp_, status, handler_context);
}
break;
case 3:
{
HandlerUploadContext *h = (HandlerUploadContext *)handler_context;
Status status = upload(&h->ctx_, &h->req_, &h->resp_);
h->status_ = 2;
h->responder_.Finish(h->resp_, status, handler_context);
}
break;
}
});
}
}
private:
Status http(ServerContext *context, const HttpRequest *request,
HttpResponse *response)
{
response->set_httpresult("http is ok");
return Status::OK;
}
Status download(ServerContext *context, const DownloadRequest *request,
DownloadResponse *response)
{
response->set_downloadresult("download is ok");
return Status::OK;
}
Status upload(ServerContext *context, const UploadRequest *request,
UploadResponse *response)
{
response->set_uploadresult("upload is ok");
return Status::OK;
}
};
参考博文：https://www.cnblogs.com/oloroso/p/11345266.html
线程池源码
其中可以使用线程池同时运行多个RPC请求的接口，线程池的代码此处也一并放出来了，来源于github
github地址：https://github.com/progschj/ThreadPool.git
#ifndef THREAD_POOL_H
#define THREAD_POOL_H
#include <vector>
#include <queue>
#include <memory>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>
#include <functional>
#include <stdexcept>
class ThreadPool
{
public:
ThreadPool(size_t);
template <class F, class... Args>
auto enqueue(F &&f, Args &&...args)
-> std::future<typename std::result_of<F(Args...)>::type>;
~ThreadPool();
private:
// need to keep track of threads so we can join them
std::vector<std::thread> workers;
// the task queue
std::queue<std::function<void()>> tasks;
// synchronization
std::mutex queue_mutex;
std::condition_variable condition;
bool stop;
};
// the constructor just launches some amount of workers
inline ThreadPool::ThreadPool(size_t threads)
: stop(false)
{
for (size_t i = 0; i < threads; ++i)
workers.emplace_back(
[this]
{
for (;;)
{
std::function<void()> task;
{
std::unique_lock<std::mutex> lock(this->queue_mutex);
this->condition.wait(lock,
[this]
{ return this->stop || !this->tasks.empty(); });
if (this->stop && this->tasks.empty())
return;
task = std::move(this->tasks.front());
this->tasks.pop();
}
task();
}
});
}
// add new work item to the pool
template <class F, class... Args>
auto ThreadPool::enqueue(F &&f, Args &&...args)
-> std::future<typename std::result_of<F(Args...)>::type>
{
using return_type = typename std::result_of<F(Args...)>::type;
auto task = std::make_shared<std::packaged_task<return_type()>>(
std::bind(std::forward<F>(f), std::forward<Args>(args)...));
std::future<return_type> res = task->get_future();
{
std::unique_lock<std::mutex> lock(queue_mutex);
// don't allow enqueueing after stopping the pool
if (stop)
throw std::runtime_error("enqueue on stopped ThreadPool");
tasks.emplace([task]()
{ (*task)(); });
}
condition.notify_one();
return res;
}
// the destructor joins all threads
inline ThreadPool::~ThreadPool()
{
{
std::unique_lock<std::mutex> lock(queue_mutex);
stop = true;
}
condition.notify_all();
for (std::thread &worker : workers)
worker.join();
}
#endif
