Development of Distributed Programming Developing Tool-Kit Based on Object Group Model

Transcription

1 Development of Distributed Programming Developing Tool-Kit Based on Object Group Model Jeong-Taek Lim, Su-Chong Joo School of Electrical, Electronic and Information Engineering, Wonkwang University, Korea {jtlim, Chang-Sun Shin School of Information and Communication Engineering, Sunchon National University, Korea Abstract In this paper, we defined the concept of the grouped distributed objects[10-14], as a logical unit of distributed application service, and developed a distributed programming developing tool-kit based on object group model(ogm-dpd Tool-Kit). This Tool- Kit can provide not only dynamic binding strategy among distributed objects and distributed services using the Distributed Object Group Framework (DOGF) we constructed before, but also implementation of distributed applications easily. Based on the DOGF, this OGM-DPD Tool-Kit provides the functionalities of the register/withdraw management, the access security management for individual distributed object, and the object name/property management as group units in the point of view of distributed object management. In the point of view of distributed service, our Tool-Kit includes the DOGF that can support naming service, dynamic binding service, replication service, and load balance service for distributed application services. In this paper, we in details specified the object group model and the architecture of the DOGF supporting this Tool-Kit. Finally, we implemented a simple distributed application using this Tool-Kit, and showed the execution of this application to verify the executabilities of the distributed object group management and the distributed services described above. 1. Introduction Recently, while Intra/Inter-networking distributed environments have been constructing, the existing applications have been converting the distributed applications for sharing various distributed resources among them. For this reason, distributed system environments are required the complicated interactions among them for improving availability of distributed resources. Hence, we need to solve the complicated interactions through effective management of distributed resources, like object group management, and provide simple binding and real-time strategies for increasing the availability of resources located on distributed systems[1,2,3,4,5]. The solutions of these requirements have been researched on area of the distributed middleware and platform. Especially, many researchers are interested in the group management of distributed objects for supporting a logical single view system environment and reducing interactions among them. As some of the representative researches related to the object group concepts, the Common Object Request Broker Architecture(CORBA)[6,7] and the Telecommunications Information Networking Architecture(TINA)[8,9] suggested the management model of distributed objects. These models included the concept of object group to manage distributed objects efficiently. But these studies have only considered the group service by modifying the part of CORBA-ORB, and have not been including the group management scheme and the dynamic binding strategy of single or replicated objects with the same service property in the side of the management of object groups. Hence, after considering with their specifications and our object group strategies, we developed Distributed Object Group Framework(DOGF) [10,11]. And based on the DOGF, we develop the tool-kit for implementing distributed programs having nothing to use with any middleware and any programming language. This Tool-Kit can manage the objects and object groups and apply the various distributed services by defining system resources, such as service objects, adaptively configuring the distributed application.

2 The remainders of this paper are organized as follows. In Section 2, we describe the definition of object group and the architecture of the DOGF, which are previous works to develop the OGM-DPD Tool- Kit. And in Section 3, we implement this Tool-Kit including the distributed services and the functions provided by the DOGF. In Section 4 finally, using this Tool-Kit developed, we show the execution of distributed application to verify the executablities of distributed object groups management and distributed services. Section 5 summaries our conclusion remarks and future works. 2. Our previous works 2.1. Definition of object groups Distributed applications may consist of one or more client/server objects as non-replicated objects or replicated objects located sporadically on distributed systems, and these distributed objects can be shared by several distributed applications. In this paper, we define that the object group is a set of distributed objects needed to execute a distributed application. The big distributed applications may be configured by one or more object groups. The object group can be managed by a logical single view system for sharing resources with a group or between groups, though these objects in a group are located in distributed systems physically. In the logical single view system, that is, all of objects in the object group must be transparently managed and appropriately serviced for executing a distributed application. Figure 1 is showing a logical domain with one of more object groups corresponding to a distributed application. Figure 1. Object groups corresponding to distributed applications 2.2. Distributed Framework Based on Object Group Model We have been studying the object-oriented technologies managing of the object group that can improve the executabilities of the distributed application by providing distributed transparency to clients[10,11,12,13.14]. As to components of the distributed framework based on object group model, after this we called the Distributed Object Group Framework(DOGF), for supporting object group management, our DOGF contains the objects, the Group Manager(GM) object, the Security object, the Information Repository object, and the Dynamic Binder object. For real-time services, the Real-Time Manager(RTM) objects and Scheduler objects exist in our framework. The objects, as service objects, may exist as the type of replicated objects with the same service property. Figure 2 shows the architecture of the distributed framework based on object group model. Figure 2. Architecture of distributed framework based on object group model

3 The DOGF is located on the upper layer of the Commercial-Off-The-Shelf(COTS) middlewares and the operating system and communication network. Here we use the Time-triggered Message-triggered Object Supporting Middleware(TMOSM) developed by DREAM Lab. at University of California at Irvine instead of COTS middleware. The distributed applications located on the top layer can be implemented by one or more service objects, briefly called objects, with non real-time or real-time properties. With components functions and their interactions in the framework, the Group Manager object is responsible for wholly managing distributed objects including in an object group, and is a unique interface for interacting with arbitrary external clients in the same object group or others. The client requests an appropriate object for executing a distributed application via the Group Manager object. And then, the Security object checks the access rights of the requesting object by applying security policy for the service request of client object. In next phase, the Group Manager object asks the Information Repository object for obtaining the reference of the invoked object. The Information Repository object stores the objects properties to the object list. If the object exists nonreplicated, the Information Repository object returns the appropriate reference of the object to the Group Manager object. The Dynamic Binder object includes the binding priority list for each replicated object in the Information Repository object, receives the service request from the Information Repository object, and finally returns the corresponding reference to the Group Manager object after selecting the appropriate object. At this time, in accordance with the executing characteristics of a given application, we can adapt the various binding algorithms to the Dynamic Binder object for getting high performance. The Real-Time Manager object receives the deadline information from the client, calculates the service deadline by referring time constraints, and requests the real-time scheduling to the Scheduler object. And then, the Scheduler object includes the task priority list for the requested tasks that object executes, and schedules the requested tasks by using the client object s information and the deadline information. In the same manner as the Dynamic Binder object, we can adapt the various realtime algorithms to the Scheduler object by the applications characteristics. Also, the Real-Time Manager object and the Scheduler object are used selectively, according to distributed application s realtime property. In the view of distributed object groups management, through above components, the DOGF supports the group register/withdrawal management of objects corresponding to the distributed application, the access security management for object, and the object name/property management. In the view of distributed services, this DOGF provides the naming service, dynamic binding service, replicated object supporting service, and load balance service for distributed application services. In our previous paper [14], we verified the executability of the supporting services by applying the DOGF to the distributed defense system as an example of distributed applications. 3. Implementation of OGM-DPD Tool-Kit The OGM-DPD Tool-Kit includes the Distributed Object Group Framework(DOGF) mentioned in Section 2. When programming a distributed application, the DOGF in the Tool-Kit supports the group management and the distributed services by calling the simple Application Program Interfaces(APIs) so that programming developers can conveniently implement distributed applications. Figure 3 is showing the various programming environments of distributed applications using the OGM-DPD Tool-Kit. This Tool-Kit provides the developing environment of distributed application independently from any kind of application programming language and distributed middleware. The components supporting object group management and distributed service in our Tool-Kit are implemented to packaging DLL(Dynamically Linked Library). Figure 3. Developing environments of distributed program using OGM-DPD Tool-Kit 3.1. Functional interfaces of OGM-DPD Tool- Kit The Group Manager object in the DOGF is responsible for wholly managing distributed objects including in an object group as the executing unit of distributed application, and is a unique object in an object group interfacing with client object. The distributed objects configuring an application take the

4 group register/withdraw, the security check, the dynamic binding service and so forth via the functional interfaces implemented in the Group Manager object. Figure 4 shows the functional interfaces of the Group Manager object for managing group from this Tool-Kit. We used the C++ as an object oriented program language for developing the Tool-Kit s components. #include "DOGST_DLL.h" class GroupManagerObject { //register an object to the object group. char* enter_objectgroup(char *group_name, char *service_name, char *object_name, char *location_address); //withdraw an object from the object group. char* withdraw_objectgroup(char *group_name, char *service_name, char *object_name); //modify an object s info. registered in the object group. char* modify_objectgroup(char *service_name, char *group_name, char *object_name, char *location_address); //insert access right of objects for client. char* insert_access_right(char *client_name, char *group_name, char *service_name); //delete access right of client for objects. char* delete_access right(char *client_name, char *group_name, char *service_name); //request the object s reference for executing service. char* request_object_infotoiro(char *client_name, char *group_name, char *service_name); }; Figure 4. Functional interfaces of the Group Manager object The remaining components of the DOGF supporting in the OGM-DPD Tool-Kit are implemented in the same way as the implementation of the Group Manager object. The detailed functions and the structure of components are referred to [10,11,14] GUI Environments of OGM-DPD Tool-Kit While programming by using this Tool-Kit, server or client programming developers can develop the distributed application independently from their developing environments, that is, such as application program languages and distributed middlewares. For achieving the Tool-Kit s goal mentioned above, we implemented with 3 Graphical User Interface (GUI) environments as followings; GUI for object group administrator, GUI for server programming developer, and GUI for client programming developer. The first GUI wholly manages the executing environment of distributed application. The second GUI is responsible for the group register/withdraw and the access right of objects of server program. And, the third GUI, by searching distributed applications provided as object groups, supports the developing environment of the client program that requests distributed service. By using these GUIs, the distributed application developers can conveniently use the supporting functions provided from the DOGF. Server programming developers make a server program on specialized server systems, and register these server objects to the DOGF via GUIs of our Tool-Kit. Also, client programming developers search the server objects provided by the object group via this Tool- Kit s client GUI, and then they make a client program by only referring to the corresponding server objects providing by server systems. By this manner, client programming developers can reduce the distributed application s developing time by reusing the existing distributed objects already made by server programming developers. The following subsections explain the functions of each GUI environment GUI for object group administrator This GUI supports the group management of distributed objects and the dynamic binding strategies to help the execution of distributed application. Figure 5 shows the GUI for object group administrator. In, we can use selectively binding algorithms for choosing a replicated object on a group. And, is showing that we register/withdraw the objects into the given group Operator using the service name, also grant the access right of objects to clients. The configuration and status information of the object group are displayed in. Figure 5. GUI for object group administrator GUI for server programming developer The GUI for the server programming developers is responsible for granting the access rights to clients and for implementing the components to execute distributed application, as server objects. In Figure 6, from, we set the communication environment of the DOGF to registering/withdraw these objects

5 into/from the object group. In, we register the object corresponding to the distributed application into the group by the service name, also set the access right to clients for the corresponding services. The configuration and status information about the object group are displayed in. The server and the client programming developers develop their programs in each system, respectively. These programs are independent with each other. Hence, this Tool-Kit has to support interactions between them transparently without concerning the physical location of distributed objects, when an arbitrary client takes the access right of server objects from object group administrator or server programming developer. Figure 6. GUI for server programming developer GUI for client programming developer In GUI for client programming developer, it provides the distributed objects with the access right permitted to clients for developing distributed applications. By using in Figure 7, in the same as setting GUI for server programming developer, we set the communication environment with the framework for accessing the object group and the objects available by the client. After then, with pressing the Search button, the available object groups and objects accessing by the underlying client are shown in. Client programming developers can easily develop a distributed application for clients using these objects permitted by object group administrator or server programming developer. Figure 7. GUI for client programming developer 4. Development procedure of distributed program using OGM-DPD Tool-Kit In this Section, we show the convenience of distributed program development and the executability of distributed services by using the OGM-DPD Tool- Kit. Fist of all, we implemented a distributed application based on the Time-triggered Messagetriggered Object(TMO) scheme and the TMO Support Middleware(TMOSM), and examined its execution results. The TMO scheme and TMOSM are the realtime supporting object models suggested by DREAM Lab. at UCI[15]. Detailed characteristics and structure of the TMO scheme are explained in [16,17]. Because the TMO scheme, in this paper, supports the distributed real-time service itself, we did not implement the real-time servicing modules, the Real- Time Manager object and the Scheduler object in the DOGF. Here for applying the concepts of replication service to our Tool-Kit, we used the dynamic binding strategy instead of the static binding strategy supported in the TMOSM for connecting with client and server objects Experimentation of OGM-DTP Tool-Kit using a simple application This section shows a distributed application with 4 operations(add( ), subtract( ), multiple( ), divide( )) registered in the DOGF by using the OGM-DPD Tool- Kit. These operations are implemented to the TMO objects on 2 systems as follows; Add_TMO1, Add_TMO3, Subtract_TMO, and Multiple_TMO objects are located on System A, and Add_TMO2 and Divide_TMO objects are located on System B. Add_TMO1, Add_TMO2, and Add_TMO3 are replicated objects with the same service property, add( ). According to the clients request, Binding algorithm must select an optimal object being on distributed systems with the minimum overhead from replicated objects. Before implementing of an application, these objects are managed by object group administrator, as a unit of group, Operator. Client programming developers ought to take access right of these objects necessary to application from object group administrator or server programming developer. The detailed development processes of distributed application using this Tool-Kit are as follows. Each server programming developer implements the object providing the corresponding service on the server system. And then, the implemented objects have to register to the object group, Operator, and grant the access right to clients. Client programming developers

6 search the distributed services permitted as object groups on GUI for client programming developer on this Tool-Kit. Client programming developers implement a client program using only the permitted objects. The server and the client programming developers can make their programs independently via our Tool-Kit. Figure 8 shows the executing processes of the distributed application mentioned above. Figure 8. Executing processes of the TMO-based distributed application In the first step, the client requests the reference of object executing the add() service to the Group Manager object. Next, the Group Manager object checks the access right of the object that provides the corresponding service for the client request. And, if possible to access them, the Group Manager object requests the object s reference to the Information Repository object. The Information Repository object examines the replication status of objects. At this time, if the object exists non-replicated, the Information Repository object returns the object s reference immediately. If the objects are replicated objects(add_tmo1, Add_TMO2, and Add_TMO3), the Information Repository object requests the selection of object s reference for object binding to the Dynamic Binder object. After this, the Group Manager object returns the object s reference(add_tmo2) selected to the client. Finally, the client requests the service to the object by referring to the object reference received from the OGM-DPD Tool-Kit, and receives the executing results Development of client program using OGM-DPD Tool-Kit Via referring objects in a group shown on the client developer s GUI in Figure 7, the client programming developers can make a distributed application independently without considering server environment. For this, the server programming developers have to register the referred objects to the Information Repository object that is a component consisted in the DOGF. After then objects in the rectangle box of left side must to be declared in client program, like the type declaration of general programming language. In details, the Operator group and the Print group are registered in the DOGF. And the former group has the objects for executing add( ), subtract( ), multiple( ), and divide( ) services and the latter group has the objects for executing printer( ) and monitor( ) services. The remaining parts for developing a client program are equal to the existing program mechanisms. Figure 9 and Figure 10 are showing the examples of client programs implemented by the TMO-based C++ and the RMI(Remote Method Invocation)-based Java languages with the OGM-DPD Tool-Kit, respectively. Figure 9. TMO-based client program developed by C++

7 4.3. Executing results of client program Figure 10. RMI-based client program developed by Java Figure 11 shows the executing results of the client program implemented in Figure 9. The client program requests the objects for executing add( ), subtract( ), and divide( ) services in the Operator group from server systems, repeatedly. Here we assume that requesting client cannot take the access right for multiple( ) service from a server programming developer. In this figure, we showed the service results and their interactions while invoking objects in the distributed environment as shown in Figure 8. Considering that a client requests one of the replicated objects(add_tmo1, Add_TMO2, and Add_TMO3) for receiving the result of add( ) service, the OGM- DPD Tool-Kit returns the appropriate object s reference out of replicated objects to the client by operating the dynamic binding service and the client requests the service by referring the returned object s reference. Finally, the client receives the executing results from the object. We adapted the Random algorithm out of several binding algorithms to the Dynamic Binder object in the DOGF for selecting one object out of 3 replicated objects described above. From Figure 11, the first 4 requests remotely call the add( ) service and receive each executing result of its service, as a sequence of Add_TMO2, Add_TMO3, Add_ TMO1, and Add_TMO3 selected by Random algorithm. The 5 th and final 7 th requests invoke Subtract_TMO and Divide_TMO and receive each executing result of these services, respectively. Finally, the 6 th request is denied due to not taking the access right about the multiple( ) service. Figure 11. Execution results of client program 5. Conclusions and future works In this paper, we developed the distributed programming developing tool-kit based on object group model(ogm-dpd Tool-Kit) which can provide not only dynamic binding among distributed objects and distributed services using the Distributed Object Group Framework(DOGF) we constructed before, but also implement distributed applications easily. The OGM-DPD Tool-Kit includes the DOGF that can support naming service, dynamic binding service, replication service, and load balance service for distributed application services. From the experimental results of the distributed application developed by using this Tool-Kit, we

8 showed that it is possible to execute the group management of objects configuring the distributed application and the dynamic binding for the replicated objects, and to provide conveniently the easy developing environment for programming distributed applications via supporting the Tool-Kit s 3 GUI environments. In future works, we are planning to add and extend the service component interfaces that can integrate the OGM-DPD Tool-Kit with a Framework supporting the Healthcare Home Service over the ubiquitous computing environment that can totally manage the healthcare devices, healthcare appliance, biosensors, and medical information systems. Acknowledgements. The authors wish to acknowledge helpful discussions of the TMO Programming Scheme with Professor Kane Kim in DREAM Lab., University of California at Irvine. This research was supported by the Korean Ministry of Science and Technology through the Center for Healthcare Technology and Development. References [1] Bellissard, L., Boyer, F., Riveill, M., and Vion-Dury, J.- Y., System Services for Distributed Application Configuration, In Proceedings of the 4th International Conference on Configurable Distributed Systems, 1998, pp [2] M. Takemoto, Fault-Tolerant Object on Network-wide Distributed Object-Oriented Systems for Future Telecommunications Applications, In IEEE PRFTS, 1997, pp [3] P.M. Melliar-Smith, L.E. Moser, and P. Narasimhan, Consistent object replication in the Eternal System, Theory and Practice of Object System, Vol.4, No.2, 1998, pp [4] V. Kalogeraki, P.M. Melliar-Smith, and L.E. Moser, Dynamic Scheduling for Soft Real-Time Distributed Object Systems, In Proceedings of the IEEE 3rd International Symposium on Object-Oriented Real-Time Distributed Computing, 2000, pp [5] G. Cooper, L. DiPippo, L. Esibov, R. Ginis, R. Johnston, P. Kortman, P. Krupp, J. Mauer, M. Squadrito, B. Thuraisingham, S. Wohlever, and V. Wolfe, Real-Time CORBA Development at MITRE, NRaD, Tri-Pacific and URI, In Proceedings of IEEE Workshop on Middleware for Distributed Real-time Systems and Services, 1997, pp [6] Object Management Group, The Common Object Request Broker: Architecture and Specification 2.2, [7] OMG Real-time Platform SIG, Real-time CORBA a White Paper-Issue 1.0, realtime/real-time_whitepapers.html, [8] L. Kristiansen, P.Farley, R.Minetti, M. Mampaey, P.F. Hansen, and C.A. Licciardi, TINA Service Architecture and Specifications, [9] Axel Kupper, Locating TINA User Agents: Strategies of a Broker Federation and their Comparison, In Proceedings of the 6th International Conference on Intelligence in Services and Networks(IS&N), [10] C.S. Shin, M.H. Kim, Y.S. Jeong, S.K. Han, and S.C. Joo, Construction of CORBA Based Object Group Platform for Distributed Real-Time Services, In Proceedings of the 7th IEEE International Workshop on Object-oriented Real-time Dependable Systems(WORDS 02), 2002, pp [11] S.C. Joo, C.S. Shin, C.W. Jeong, and S.K. Oh, CORBA Based Real-Time Object-Group Platform in Distributed Computing Environments, Lecture Notes in Computer Science, Vol.2659, 2003, pp [12] C.S. Shin, M.H. Kim, and S.C Joo, A Construction of TMO Object Group Model for Distributed Real-Time Services, The Transaction of Korea Information Science Society, Vol.30, No.5-6, 2003, pp [13] C.S. Shin, M.S. Kang, Y.S. Jeong, S.K. Han, and S.C. Joo, TMO-Based Object Group Model for Distributed Real-Time Services, Proceedings of IASTED International Conference-Networks, Parallel and Distributed Processing, and Applications(NPDPA 2002), 2002, pp [14] Chang-Sun Shin, Chang-Won Jeong, and Su-Chong Joo, Construction of Distributed Object Group Framework and Its Execution Analysis Using Distributed Application Simulation, Lecture Notes in Computer Science, Vol.3207, 2004, pp [15] K.H. Kim, Object-Oriented Real-Time Distributed Programming and Support Middleware, In Proceedings of the 7th International Conference on Parallel and Distributed Systems, 2000, pp [16] K.H. Kim, Seok-Joong Kang, and Yuqing Li, GUI Approach to Generation of Code-Framworks of TMO, In Proceedings of the 7th IEEE International Workshop on Object-oriented Real-time Dependable Systems(WORDS), 2002, pp [17] Kim, K.H., Ishida, M., and Liu, J., An Efficient Middleware Architecture Supporting Time- triggered Message-triggered Objects and an NT-based Implementation, In Proceedings of the IEEE CS 2nd International Symposium on Object-oriented Real-time distributed Computing(ISORC'99), 1999, pp [18] S.C. Joo, C.S. Shin, and J.T. Lim, Distributed Programming Developing Tool-Kit Based on Object Group, Program License by Korea Computer Program Deliberation & Mediation Committee, 2005, Grant- No