Brpc source code analysis (VIII) -- detailed explanation of the basic class eventdispatcher

I was busy a while ago , It hasn't been updated for a long time , Strive to restore the update frequency in the future , This time, I'll start with a relatively simple , introduce EventDispatcher class , The previous article dealt with this concept , EventDispatcher, seeing the name of a thing one thinks of its function , It is used to distribute events , stay brpc Inside , Because there is no distinction io Threads and user threads , This EventDispatcher, It is only used for event distribution , Not responsible for specific data reading and writing , So its throughput can be very large . This class is important , But itself is relatively simple , Here are the core functions and class variables .

1. Start related functions

（1）void Run()
Core function , call epoll_wait Wait for the event and call the function to process ,epoll_in Call after the event Socket:: StartInputEvent,epoll_out Call after the event Socket::HandleEpollOut,Socket:: StartInputEvent and Socket::HandleEpollOut It is to execute the corresponding socket The corresponding user processing function in . The core code is as follows ：

（2）static void* RunThis(void* arg);
Encapsulates the Run, Used in bthread Start the call in Run.

（3）virtual int Start(const bthread_attr_t* consumer_thread_attr);
newly build bthread With RunThis Start the current EventDispatcher, Start listening epoll Event and distribute .

2. add to epoll_in Event function

int AddConsumer(SocketId socket_id, int fd)
stay fd Add epoll_in event （ Can read the event ） monitor , Parameters socket_id Will be saved to the added event , The following events happened, which need to be based on this socket_id address Actually socket, Take the inside _on_edge_triggered_events Wait for actual processing , To sum up, call this function to add the required socket_id Corresponding socket To deal with occurs in fd The edge on triggers epoll_in event . What is called directly after the event is Socket:: StartInputEvent.

3. add to epoll_out Event function

AddEpollOut(SocketId socket_id, int fd, bool pollin)
Add listening epoll_out event （ Can write event ）, And add epollin In a similar way ,epoll_out event , One more. pollin Parameters , If true They'll listen at the same time epoll_in, What is called directly after the event is Socket::HandleEpollOut, For example, the previous article mentioned ,brpc It's going somewhere socket When writing data in , If it is not connected yet, initiate the connection and use “ Continue to write the function ” Register as a callback epollout Back directly , Let the callback complete the subsequent write operation .

4. obtain EventDispatcher function

Brpc Support multiple EventDispatcher, Specifically EventDispatcher The quantity is determined by the parameters , The default quantity is 1, Every EventDispatcher Responsible for part of fd Monitoring and processing of .
each fd All calls GetGlobalEventDispatcher To get the corresponding EventDispatcher, This function is right here event_dispatcher.cpp in ,EventDispatcher Out of class brpc namespace The next function , as follows ：

If it is not initialized, it will be initialized and run first ,InitializeGlobalDispatchers Is a specific initialization function , from pthread_once Promise to do it only once . This is based on MurmurHash3 take fd Distribute evenly to each EventDispatcher.InitializeGlobalDispatchers Function as follows ：

5. Core class variables

（1）int _epfd： Monitoring events epfd
（2）bthread_t _tid：EventDispatcher Current bthread Of id
（3）bthread_attr_t _consumer_thread_attr：epoll_in perhaps epoll_out New after the event bthread Thread properties used to execute user callback functions