ceph Dispatcher模塊分析 原

Dipatcher類是消息分發的接口，OSD、MON、等類都繼承該類，並實現了Dipatcher的消息分發接口

     1079 class OSD : public Dispatcher,
-    1080         public md_config_obs_t {
|    1081   /** OSD **/

      128 class Monitor : public Dispatcher,
-     129                 public md_config_obs_t {
|     130 public:
|     131   // me
|     132   string name;

在OSD::init()函數中把不同類型的Dipatcher加入到SimpleMessenger實例中

|    2146   // i'm ready!
|    2147   client_messenger->add_dispatcher_head(this);
|    2148   cluster_messenger->add_dispatcher_head(this);
|    2149 
|    2150   hbclient_messenger->add_dispatcher_head(&heartbeat_dispatcher);
|    2151   hb_front_server_messenger->add_dispatcher_head(&heartbeat_dispatcher);
|    2152   hb_back_server_messenger->add_dispatcher_head(&heartbeat_dispatcher);
|    2153 
|    2154   objecter_messenger->add_dispatcher_head(service.objecter);

在Messenger::add_dispatcher_head(Dispatcher *d)中加入Messenger::list<Dispatcher*> dispatchers中，並調用ready（）,SimpleMessenger::ready()重寫了基類的ready，

|-   358   void add_dispatcher_head(Dispatcher *d) {
||   359     bool first = dispatchers.empty();
||   360     dispatchers.push_front(d);
||   361     if (d->ms_can_fast_dispatch_any())
||   362       fast_dispatchers.push_front(d);
||   363     if (first)
||   364       ready();
||   365   }

在ready函數中調用DispatchQueue::start, start()函數啓動DispatchQueue::DispatchThread和DispatchQueue::LocalDeliveryThread線程類，最終調用DispatchQueue::entry()和DispatchQueue::run_local_delivery。

     216 void DispatchQueue::start() 
-    217 {   
|    218   assert(!stop);
|    219   assert(!dispatch_thread.is_started());
|    220   dispatch_thread.create("ms_dispatch");    //調用Thread::create->Thread::try_create->Thread::_entry_func->Thread::entry_wrapper->DispatchThread::entry
|    221   local_delivery_thread.create("ms_local");
|    222 }     

|-    98   class DispatchThread : public Thread {
||    99     DispatchQueue *dq;
||   100   public:
||   101     explicit DispatchThread(DispatchQueue *dq) : dq(dq) {}
||-  102     void *entry() {
|||  103       dq->entry();
|||  104       return 0;
|||  105     }  
||   106   } dispatch_thread;

在DispatchQueue::entry()中調用根據不同的命令碼調用不同的Messenger類中的處理函數

void DispatchQueue::entry()
{
    .
    .
 
	switch (qitem.get_code()) {
	case D_BAD_REMOTE_RESET:
	  msgr->ms_deliver_handle_remote_reset(qitem.get_connection());
	  break;
	case D_CONNECT:
	  msgr->ms_deliver_handle_connect(qitem.get_connection());
	  break;
	case D_ACCEPT:
	  msgr->ms_deliver_handle_accept(qitem.get_connection());
	  break;
	case D_BAD_RESET:
	  msgr->ms_deliver_handle_reset(qitem.get_connection());
	  break;
	default:
	  assert(0);
	}
      } else {
	Message *m = qitem.get_message();
	if (stop) {
	  ldout(cct,10) << " stop flag set, discarding " << m << " " << *m << dendl;
	  m->put();
	} else {
	  uint64_t msize = pre_dispatch(m);
	  msgr->ms_deliver_dispatch(m);
	  post_dispatch(m, msize);
	}
      }
      .
      .

}

在Messenger::ms_deliver_dispatch中最終調用不同的Dipatcher繼承類的ms_dispatch進行處理

|-   579   void ms_deliver_dispatch(Message *m) {
||   580     m->set_dispatch_stamp(ceph_clock_now(cct));
||   581     for (list<Dispatcher*>::iterator p = dispatchers.begin();                                                                                                            
||   582      p != dispatchers.end();
||-  583      ++p) {
|||  584       if ((*p)->ms_dispatch(m))     //在Dispatcher繼承類中進行處理
|||  585     return;
|||  586     }
||   587     lsubdout(cct, ms, 0) << "ms_deliver_dispatch: unhandled message " << m << " " << *m << " from "
||   588              << m->get_source_inst() << dendl;
||   589     assert(!cct->_conf->ms_die_on_unhandled_msg);
||   590     m->put();
||   591   }