miniob源码 架构概览

miniob源码 架构概览

整体架构

如下图，简单描述了，observer启动后，建立监听、注册libevent事件，recv后触发各stags的handle_event、处理结果回调、threadpool运行机制等等几个方面对整体线程模型、reactor模型和各组件工作流进行分析。

Reactor模型

• miniob运行框架是通过libevent实现了对网络事件的监听，当链接建立后，读缓冲区事件触发回调recv函数的处理流程。

event_set(&client_context->read_event, client_context->fd, EV_READ | EV_PERSIST, recv, client_context);

• 在recv函数的最后将SessionEvent添加到SessionStage的事件队列中，同时将SessionStage添加到threapool的Stage队列中。

  SessionEvent *sev = new SessionEvent(client);
  session_stage_->add_event(sev);

• thread_pool的stage队列（thread_pool.h）

std::deque<Stage *> run_queue_;  //< list of stages with work to do

• stage_event队列（stage.h）

std::deque<StageEvent *> event_list_;  // event queue

线程模型

miniob采用多线程的架构，通过Threadpool类创建线程池，根据etc/observer.ini中的配置创建线程。

# threadpools' name, it will contain the threadpool's section
ThreadPools=SQLThreads,IOThreads,DefaultThreads

[SQLThreads]
# the thread number of this threadpool, 0 means cpu's cores.
# if miss the setting of count, it will use cpu's core number;
count=3
#count=0

[IOThreads]
# the thread number of this threadpool, 0 means cpu's cores.
# if miss the setting of count, it will use cpu's core number;
count=3
#count=0

[DefaultThreads]
# If Stage haven't set threadpool, it will use this threadpool
# This threadpool is used for backend operation, such as timer, sedastats and so on.
# the thread number of this threadpool, 0 means cpu's cores.
# if miss the setting of count, it will use cpu's core number;
count=3

ThreadPools 配置了3个线程池：SQLThreads,IOThreads,DefaultThreads，每个线程池可以配置count，即线程的个数。

• 创建线程池和线程，初始化时通过new ThreadPools，在构造函数中调用add_threads，根据线程个数的配置创建线程。

  // attempt to start the requested number of threads
  for (i = 0; i < threads; i++) {
   
   
    int stat = pthread_create(&pthread, &pthread_attrs, Threadpool::run_thread, (void