mongo源码学习（四）服务入口点ServiceEntryPoint

namespace mongo {/** * This is the entrypoint from the transport layer into mongod or mongos. * * The ServiceEntryPoint accepts new Sessions from the TransportLayer, and is * responsible for running these Sessions in a get-Message, run-Message, * reply-with-Message loop. It may not do this on the TransportLayer’s thread. *//** * 这是从transport layer到mongod或者mongos的入口点。 * * ServiceEntryPoint从TransportLayer中接收新的Session，并且负责运行这些Sessions的 * get-Message，run-Message和reply-with-Message生命周期。它可能不会在TransportLayer的线程 * 中这些事情。 */class ServiceEntryPoint { MONGO_DISALLOW_COPYING(ServiceEntryPoint);public: virtual ~ServiceEntryPoint() = default; /** * Begin running a new Session. This method returns immediately. */ /** * 开始一个新的Session。这个方法会马上返回。 */ ; /** * End all sessions that do not match the mask in tags. */ /** * 结束所有和tags中掩码不匹配的sessions。 */ ; /** * Starts the service entry point */ /** * 启动服务入口点。 */ ; /** * Shuts down the service entry point. */ /** * 关闭服务入口点。 */ ; /** * Append high-level stats to a BSONObjBuilder for serverStatus */ /** * 为serverStatus向BSONObjBuilder追加高级状态。 */ ; /** * Returns the number of sessions currently open. */ /** * 返回当前打开的sessions数量。 */ ; /** * Processes a request and fills out a DbResponse. */ /** * 处理一个请求并写入DbResponse。 * P. S. 敲黑板了， 同志们，这里就是处理请求的地方了啊！ */ ;protected: ServiceEntryPoint() = default;};} // namespace mongo

namespace mongo {class ServiceContext;namespace transport {class Session;} // namespace transport/** * A basic entry point from the TransportLayer into a server. * * The server logic is implemented inside of handleRequest() by a subclass. * startSession() spawns and detaches a new thread for each incoming connection * (transport::Session). *//** * 从TransportLayer到server的一个基本入口点。 * * 服务器处理请求的逻辑是通过子类的handleRequest()方法实现的。 * startSession()会spawns并且分配一个新的线程来处理每个到来的连接（transport:Session） * spawn: （鱼、蛙等）大量产（卵）;引起，酿成 * */class ServiceEntryPointImpl : public ServiceEntryPoint { MONGO_DISALLOW_COPYING(ServiceEntryPointImpl);public: // 构造函数 explicit ServiceEntryPointImpl(ServiceContext* svcCtx); void startSession(transport::SessionHandle session) override; void endAllSessions(transport::Session::TagMask tags) final; Status start() final; bool shutdown(Milliseconds timeout) final; void appendStats(BSONObjBuilder* bob) const final; size_t numOpenSessions() const final { return _currentConnections.load(); }private: using SSMList = stdx::list<std::shared_ptr<ServiceStateMachine>>; using SSMListIterator = SSMList::iterator; ServiceContext* const _svcCtx; AtomicWord<std::size_t> _nWorkers; mutable stdx::mutex _sessionsMutex; stdx::condition_variable _shutdownCondition; SSMList _sessions; size_t _maxNumConnections{DEFAULT_MAX_CONN}; AtomicWord<size_t> _currentConnections{}; AtomicWord<size_t> _createdConnections{}; std::unique_ptr<transport::ServiceExecutorReserved> _adminInternalPool;};/* * Returns true if a session with remote/local addresses should be exempted from maxConns *//* * 如果远程或本地的session可以从最大连接数约束中豁免则返回true */bool shouldOverrideMaxConns(const transport::SessionHandle& session, const std::vector<stdx::variant<CIDR, std::string>>& exemptions);} // namespace mongo