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  1. OMG Issue

CPP13 — Section: 13.6 Server mapping

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  • Key: CPP13-67
  • Legacy Issue Number: 11403
  • Status: open  
  • Source: Alcatel-Lucent ( Ou changhua)
  • Summary:

    Althrough I report my issue as a C++ issue, actually it is a common issue for other languages also. In current CORBA standard, a activated CORBA Servant object in the POA is shared by all the clients. But in many applications, a client connects to the server and calls some CORBA object methods to create a lot of connection related CORBA objects. Normally, the client will call "destroy" method of these CORBA object to destroy them before existing. But if the client exists abnormally, these created CORBA object will never be destroyed and never be used by any client. We can call this kind of CORBA object as "floating" CORBA object. The CORBA server application runs longer, the "floating" CORBA objects becomes more. And eventually, these "floating" CORBA objects will consume all the memory resources/CPU resources, then the CORBA server crashes and has to be restarted. The "floating" CORBA objects problem at the server side is not easy to be solved. For this problem, if the CORBA standard provides a method to solve it, the CORBA server will run more robust. Actually, the underlying network connection broken can be detected very effectively and rapidly. The CORBA server just simply ignores the network connection lost event and does not pass it to activated CORBA object even if the CORBA object is connection related object because current CORBA standard thinks that all the CORBA objects in the server are shared to all clients. If the server can notify the network connection lost event to the connection related CORBA objects, the developper can do the clean job on it. A simple method can solve the "floating" CORBA object problem. It is not required to add any new interface or data structure to current orb.idl. It is just required to add some new language mapping methods at server side only. I will give an example in C++ to show this simple method. A IShared,IConnSpec and IOtherConnectionSpec interfaces are defined below: interface IOtherConnectionSpec

    { ... }

    interface IConnectionSpec

    { IOtherConnectionSpec someMethod(); }

    interface IShared

    { IConnectionSpec createConnSpec( in string param ); }

    ; These interfaces will be used in this example. 1) the IShared will be shared by all the clients, it is activated like this: SharedImpl sharedImpl( ... ); ... sharedImpl._this(); 2) add new mapping method for the "POA_IShared::createConnSpec()" like this: IConnectionSpec_ptr POA_IShared::createConnSpec( char* param, const ConnectionContext& connCtx ); In this method, a parameter named ConnectionContext that represents the connection between the client and server is added. This method has a default implementation like this: IConnectionSpec_ptr POA_IShared::createConnSpec( const char* param, const ConnectionContext& connCtx )

    { //just ignore the connCtx like the current CORBA standard defines return createConnSpec( param ); }

    3) If the user wants to create a connection related object, he/she must overload the "IConnectionSpec_ptr createConnSpec( char* param, const ConnectionContext& connCtx )" method and active the object with "this_( const ConnectionContext& connCtx )" method: IConnectionSpec_ptr POA_IShared::createConnSpec( const char* param, const ConnectionContext& connCtx )

    { ... IConnectionSpec *connSpecImpl = new IConnectionSpec( ... ); ... //use the connection related active method return connSpecImpl->this_( connCtx ); }

    in this method, the user uses the "this_( const ConnectionContext& connCtx)" method instead of the old "this()"" method to active the CORBA object. This activated CORBA object becomes a connection related object instead of shared object. Note: User can use the "this_( const ConnectionContext& connCtx)" method to active a shared object also. At this time, the ConnectionContext is a global variable "NO_CONNECTION_CONTEXT". 4) add a new mapping method named "getConnectionContext()" for every CORBA object. const ConnectionContext& IShared::getConnectionContext(); const ConnectionContext& POA_IConnectionSpec::getConnectionContext(); In this way, the IConnectionSpec can create and activate any other connection related CORBA object like this: IOtherConnectionSpec_ptr POA_IConnectionSpec::someMethod()

    { ... OtherConnectionSpecImpl *otherConnSpecImpl = new OtherConnectionSpecImpl(...); ... return otherConnSpecImpl->this_( getConnectionContext() ); //or ? //return otherConnSpecImpl->this_( this ); }

    5) add a new mapping method named "connectionLost()" for every CORBA object. When the network connection is lost, the CORBA server should find all the CORBA object associated with this network connection and call their "connectionLost()" method. The "connectionLost()" and its default implementation is listed below: void POA_IConnectionSpec::connectionLost()

    { //just delete this connection related object simply delete this; } void POA_IOtherConnectionSpec::connectionLost() { //just delete this connection related object simply delete this; }

    Because the SharedImpl object that created in the 1) step does not assicate with any connection, its "connectionLost()" method will not be called for ever.

  • Reported: CPP 1.1 — Fri, 14 Sep 2007 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:58 GMT