Distributed Processing Framework

1
Distributed Processing Framework

• Behind the scenes

2
Presentation structure

• The new DPF prototype
• Architecture
• Entities and interfaces
• Working of the prototype
• DPF background

3
Design 1/2

• The need for well defined interfaces
• Interfaces need to be standardized at design
  phase
• Implemented by client and component (Agent and
  Station)
• DPF considerations
• Need to persist Agent state
• Need to remote Agent instance

4
Design 2/2

• Persisting Agent state
• STG Storage files
• IPersistStream To read and write object state
  information as an array of bytes into a storage
  file
• Remoting an Agent
• Transfer of class information
• Instantiating a remote agent
• Reviving the agent

5
Entities interfaces

• Station, Agent, StationManager
• IStation
• TransferAgentToRemoteHost(in BSTR
  szRemoteHostName, in BSTR bszComponentDllFileNam
  e, in BSTR bszAgentStateSTGFileName, in CLSID
  clsidOfAgent)
• RegisterDllComponent(in BSTR bszDllpath)
• StartAndRunAgent()
• CopyAgentStateFromShare(in BSTR
  bszAgentStateSTGFileName)
• CopyAgentSourceFromShare(in BSTR
  bszComponentDllFileName)
• IAgent
• RunAgent (in IStation pIStation)
• IPersist, IPersistStream, IPersistStreamInit
• Load(IStream pStm)
• Save(IStream pStm, BOOL fClearDirty)
• IsDirty(void)
• GetSizeMax(ULARGE_INTEGER pcbSize)
• InitNew(void)
• GetClassID(CLSID pClassID)

6
Working of the prototype

• Client-
• Create Agent component DLL
• Register Agent component
• Instantiate StationManager
• Pass to StationManager Agent IID and CLSID
• StationManager
• Instantiate Station (Load Station DLL into
  memory)
• Pass to Station Agent IID and CLSID
• Station
• Instantiate Agent (Load Agent DLL into memory)
• Call RunAgent method of Agent
• Upon TransferAgent request, create new instance
  of Station on remote machine. Send Agent DLL and
  Agent STG files
• Remote Station instantiates Agent on remote
  machine
• Remote Agent retrieves persisted state and
  continues execution
• Agent
• Execute Agent specific code (RunAgent method)
• Persist state with methods implemented by
  Ipersist
• On transfer request call TransferAgent method of
  Station

7
COM Background

• Component development
• Description of Source code
• Execution environment
• Technology and terminology
• Registry
• Compile / build time Debug time
• Software and tools

8
Component development

• Interface definition (standardization)
• Exporting to IDLs or TLBs
• Reverse engineering TLBs for type information
  (TLIs, TLHs)
• MIDL used on VC 7.0 attributed managed C
• Component registration

9
Description of source code

• StationManager.cpp
• Station.cpp
• Agent.cpp
• http//v.students.umkc.edu/vp4k3/

10
Execution environment

• Component developed as either DLL or .exe
• Component run either locally or remote
  (abstracted from client)
• Local DLL or .exe
• Remote dllhost.exe (or custom surrogate) or
  remote .exe

11
Technology and terminology

• ATL
• Active template library
• Virtual functions
• Late binding
• Member name resolution at compile time (avoid
  naming conflicts)
• Static member functions and static data elements
• Singleton components
• Inheritance
• Abstract base classes
• Virtual functions
• Pure virtual functions
• Code reuse (addition to existing code) and
  overloading
• GUIDS and guidgen.exe
• Smart pointers
• IinterfacePtr varPtr CComPtr ltinterfacegt varPtr
• HRESULTS
• VC 7.0 (yet to be released limited online
  resources)
• Attribute (Compiler, IDL )
• Dual, library, oleautomation, in, out, retval

12
Registry

• IID
• To indicate proxy stub marshaller
• CLSID
• TypeLib
• LocalServer32
• InprocServer
• RemoteHostName
• AppId
• HKeyLocalHost

13
Software and tools

• VC 7.0 (part of Visual Studio .Net)
• .Net SDK

14
Compile / build time Debug time

• Compile time
• Merge files .mrg.cpp
• .obj
• .exe
• Link time
• Symbol table
• Debug time
• Symbol file .pdb
• devenv /debugexe ltexegt symbol file path

15
Miscellaneous

• Robust code
• Checking all HRESULTS
• The Chicken and the Egg problem
• Interface declaration fiasco
• Information needed at compile time IIDs, CLSIDs,
  TLBs, IDLs

16
DPF The next step

• Implementing a singleton DPF Station component
• Providing for persisting of basic byte stream
• Comparative analysis of an Agent based scenario
  vs. a non-Agent based scenario