Darwin在转发流过程中对推送端断开的处理问题 .

最近在做项目的过程中遇到一个问题，在用Darwin Streaming Server中的QTSSReflectorModule模块做为流转发和分发服务，用live555的DarwinInjector类做为模拟设备
进行流推送时，如果按照正常RTSP推送流程:Announce、Setup、Play…、Teardown，Darwin能较好地完成流的转发，但是假如设备在不正常工作，例如网络异常断开，设备断电等中断了数据流的推送，而缺少了<设备->服务器>的Teardown过程，这样与此路推送相关的RTSPSession、RTPSession以及ReflectorSession等都需要等到配置的“rtp_timeout”时间后、RTPSession超时才能析构所有相关转发对象。

先分析下原因：
RTSPSession在创建RTPSession时
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1.// Set the current RTSP session for this RTP session.
2.// We do this here because we need to make sure the SessionMutex
3.// is grabbed while we do this. Only do this if the RTSP session
4.// is still alive, of course.
5.if (this->IsLiveSession())
6. fRTPSession->UpdateRTSPSession(this);
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1.void RTPSessionInterface::UpdateRTSPSession(RTSPSessionInterface* inNewRT
SPSession)
2.{
3. if (inNewRTSPSession != fRTSPSession)
4. {
5. // If there was an old session, let it know that we are done
6. if (fRTSPSession != NULL)
7. fRTSPSession->DecrementObjectHolderCount();
8.
9. // Increment this count to prevent the RTSP session from being de
leted
10. fRTSPSession = inNewRTSPSession;
11. fRTSPSession->IncrementObjectHolderCount();
12. }
13.}
IncrementObjectHolderCount()增加了fRTPSession对RTSPSession的引用，而对应的DecrementObjectHolderCount()在RTPSession::Teardown()中执行，由于RTSPSession 拥有很好的对象保护机制，只有当对当前RTSPSession的引用数为0时
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1.// Only delete if it is ok to delete!
2.if (fObjectHolders == 0)
3. return -1;
RTSPSession自身才能调用Task::Run(){return -1;} delete，所以在RTSPSession注销之前，必须等待RTPSession注销，而且RTPSession没有等到Teardown命令，就只能等超时，而这个超时时间不能定，及时几秒钟对于转发实时流来说也是不合理的。

解决办法：
在RTSPSession:Run()函数中的
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1.while(IsLiveSession())
2.{
3. switch(){case:}
4.}
状态机外加入代码及时析构RTPSession
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1.// Make absolutely sure there are no resources being occupied by the sess
ion
2.// at this point.
3.this->CleanupRequest();
4.
5.
6.//Kill与RTSPSession相关的RTPSession
7.if(!IsLiveSession()){
8.OSRefTable* theMap = QTSServerInterface::GetServer()->GetRTPSessionMap();
9.OSRef* theRef = theMap->Resolve(&fLastRTPSessionIDPtr);
10.if (theRef != NULL){
11. fRTPSession = (RTPSession*)theRef->GetObject();
12. if(fRTPSession) fRTPSession->Teardown();
13. theMap->Release(fRTPSession->GetRef());
14. fRTPSession = NULL;
15. }
16.}
17.// Only delete if it is ok to delete!
18.if (fObjectHolders == 0) return -1;
19.// If we are here because of a timeout, but we can't delete because someo
ne
20.// is holding onto a reference to this session, just reschedule the timeo
ut.
21.// At this point, however, the session is DEAD.
22.return 0;
注意this->CleanupRequest();在前,
这样就能在RTSPSession判断fObjectHolders之前将附属的RTPSession析构，进而析构RTSPSession.
由于工作比较忙，写的可能在思路上不是很清楚，欢迎指正！
/--------------------------------------割了------------------------------------/
在上段代码中可以加入一个补充条件进行代码的优化，并且CleanupRequest()必须在此之后！
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1.//fObjectHolders--
2.if(!IsLiveSession()&& fObjectHolders > 0){
3.OSRefTable* theMap = QTSServerInterface::GetServer()->GetRTPSessionMap();
4.OSRef* theRef = theMap->Resolve(&fLastRTPSessionIDPtr);
5.if (theRef != NULL){
6. fRTPSession = (RTPSession*)theRef->GetObject();
7. if(fRTPSession) fRTPSession->Teardown();
8. theMap->Release(fRTPSession->GetRef());
9. fRTPSession = NULL;
10. }
11.}
12.
13. // Make absolutely sure there are no resources being occupied by the s
ession
14. // at this point.
15. this->CleanupRequest();
16.
17. // Only delete if it is ok to delete!
18. if (fObjectHolders == 0)
19. return -1;。