2005/5/10

Some notes about the basic design ideas and features of ACDK ORB.

 Current Problems

 Connection Peer Pool

 The Idea

 The way

 ARB and ORB

• ARB uses build in ACDK types in most native way.
  
• ARB doesn't support struct and sequences, simply because they are superflous using ACDK types and passing them byval.
  
• In the first version ARB uses an XML type protocoll for better debugging. GIIOP should be implemented later.
  

 ARB

 ARB Basic implementation concepts

// in AnArbInteface.h
class AnArbInteface
: implements ::acdkx::arb::ArbInterface
{
  // generate Metainfo
  ACDK_WITH_METAINFO 
  // generate ARB helper
  ACDK_CORBA_INTERFACE(AnArbInteface)
public:
  // has one public method
  virtual RString getNameOfAThing(OUT(RString) name, IN(int) size) throw (RException);
};

• The class AnArbInteface_Proxy with used from the client.
  
• The AnArbInteface::orbDispatch() method, which dispatch incoming calls on the server side.
  

 Features

• Passing basic types
• Passing Strings
• passing in, out, inout
• Passing Objects by value
• Passing Interfaces
• Exceptions
• oneway
• calling objects in local process without big overhead

 ORB

 ORB Basic implementation concepts

 Sample

ACDK_DECL_INTERFACE(Hello);

/** 
  class to test with OB orb 
*/
class ACDKX_ORB_PUBLIC Hello 
: implements ::org::omg::CORBA::portable::InvokeHandler
{
  ACDK_WITH_METAINFO
public:
  ACDK_CORBA_INTERFACE(Hello)
public:
  virtual void hello() = 0;
};

ACDK_DECL_CLASS(HelloImpl);

class HelloImpl
: extends ::acdkx::orb::ServerDelegate,
  implements ::Hello
{
public:
  virtual RClass getClass() { return Hello::getClass(); }
  virtual void hello()
  {
    System::out->println("Hello Server");
  }
};

  RORB orb = ORB::init();
  RHelloImpl obj = new HelloImpl();
  orb->impl_is_ready(obj);
  RString ostr = orb->object_to_string(obj);
  RString fname = "Hello.ref";
  ::acdk::io::FileWriter f(fname);
  f.write(ostr->c_str());
  System::out->println(ostr);
  orb->run();
  

  RORB orb = ORB::init();
  RString refid;
  RString fname = "Hello.ref";
  ::acdk::io::InputReader f(new ::acdk::io::FileReader(fname));
  refid = f.readString();
  System::out->println("Calling refid: " + refid);
  RHello obj = (RHello)orb->string_to_object(refid);
  obj->hello();

 The situation

 ARB

 ORB

• Oriented at the Java portable class structure.
  
• Basic types in, out, inout
• oneway
• The operations with a very BOA are running!
  
• Basic tests with OB and mico are running!

 Outlook

 ACDK as generic CORBA server

• Polymorphic will be solved through alternative method names.
  
• For standard functions, like New, invoke, invoke_static, peek, poke, etc. will be provided by an extra interface (see AcdkObject idl below).
  
• Generate IDL-defintions with altnames as methods names.
  
• For New and the static version of methods/peek/poke Create a Factory class, which exports names by IDL.
  These Factory classes should be ordinary ACDK Classes.
  

 ACDK as generic CORBA client

• Cannot use standard DMI invoke interface and try to call CORBA services by standard marschaling with the risk of hanging.
  Main-Problem, there is no hint for the type of the return value.
  CorObject with hint to an given interface, without generating static skeleton.
  
• Make use of the DmiProxy!
  Has to rewrite DmiProxy, to provide DMI-Bridge (calling the server) also ClazzInfo and MethodInfo (for the type of the return value).
  
• Make use of the Interface-repository?
  
  

 Standard CORBA client DMI interface

/**
  Interface definition for calling any ACDK object
*/

interface AcdkObject
{
  typedef sequence<any> Params;
  AcdkObject New(in string classname, in string constructor, in Params outp, out Params inp);
  any invoke(in string methodname, in Params outp, out Params inp);
  any invoke_static(in string classname, in string methodname, in Params outp, out Params inp);
  any peek(in string membername);
  any peek_static(in string classname, in string membername);
  void poke(in string membername, in any value);
  void poke_static(in string classname, in string membername, in any value);
};

 Following issues has to be clarified:

• Classes for Stup/Proxy
  • How make it simple to implement interfaces without many overhead.
    
  • Which classes should be super classes for interfaces?
    
  • One base implementation for CORBA/DCOM/SOAP or different?
    
  • How to avoid to generade meta information for the implemention, and only for the interfaces.
    
• Dynamic DMI
  • Replace the old DMI mechanism with new flexible CORBA-DMI mechanism.
    
• Metainfo
  • Use/enhance acdk Metainfo for IR?
    
• CORBA Services
  • Which services should be implemented, which used from 3thrd party?
    
  • Which services should be implemented first?
    
• Native ACDK CORBA support
  • Moving the basic CORBA stup/skeleton into the core package
  • support all classes/interfaces with CORBA-Support
• DCOM and RMI support
  • Implement DCOM support for the CORBA-Classes
  • Implement RMI support for the CORBA-Classes.
    
  • Incompatibilities?