Summary Performance problems in a cloud service are difficult to diagnose because they may be caused by various system components. This study proposes an automatic cloud service testing and bottleneck detection system that is applicable to different types of services. With the proposed test module, the user can customize test scenarios to automatically test and collect the corresponding metrics of the target service. Afterward, the proposed bottleneck detection algorithm analyzes the collected metrics and determines whether a bottleneck is presented in the target system. The bottleneck detection module also provides a scaling recommendation for the service provider to facilitate the service system reconfiguration. The experimental results reveal that the proposed system could detect a potential bottleneck in a service system accurately. In accordance with the scaling recommendation, the performance of the target cloud service can be improved efficiently after reconfiguration. Therefore, usage of the proposed system can ensure a high quality of service, and the service level objective could be fulfilled.

Previous application sharing systems have no unified communication protocols. The well known application sharing protocols include RFB (remote framebuffer), RDP (remote desktop protocol) and ITU-T T.128. A generic application sharing architecture is proposed for providing the capability of connecting various application sharing servers with the same application sharing client. A communication standard for application sharing systems is defined based on the message-oriented middleware (MOM). To compare with previous application sharing systems, there are many advantages including easy to use, easy to connect, easy to integrate, higher scalability and less bandwidth consumption

Object oriented database system (OODB) supports an object oriented data model with the functionality of persistency and transaction semantics. In order to facilitate the use of OODB, the Object Database Management Group (ODMG) defined a standard for object database management systems. On the other hand, the Object Management Group (OMG) defined the Common Object Request Broker Architecture (CORBA), which is an emerging standard of distributed object technology providing the interconnection network between distributed objects. For the sake of matching these two object models, taking the advantages of merging both of them, and building a more sophisticated infrastructure, the integration of CORBA and OODB is currently an urgent and important issue in distributed object systems. Instead of using Object Database Adapter (ODA) suggested by the ODMG, we provide a novel way of reusing the Object Transaction Service (OTS) and wrapping techniques to introduce OODB into CORBA automatically. Through our design, CORBA clients or OODB object implementers do not need to learn any knowledge of each other. In addition, error recovery is also provided to guarantee the consistency of object states. The whole task for integrating CORBA and OODB is done transparently by our proposed preprocessor, which plays an important role in solving problems encountered by ORB and OODB vendors easily.

The concept of transactions is not only indispensable in database applications, but also useful in building robust software for mission critical applications. The paper presents an implementation of the Object Transaction Service (OTS) based on CORBA 2.0 specification. Transactional applications developed with the support of our OTS implementation are able to assure the ACID properties even in the presence of node crashes, software system failures and process hangs. The preliminary results obtained from the experiments on Sun workstations with Orbix 1.3 show that the overhead due to the OTS service is satisfactory for most applications.