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Computer systems are becoming increasingly complex. This makes it more and more difficult to ensure their correct operation and to correct errors promptly. Due to their increasing use the focus of this work is fault tolerance for OSGi-based, distributed applications. The designed concept increases the reliability of such applications while it remains perfectly hidden and doesn't interfere with their normal operation. A service that has been made fault tolerant using the developed concept does not differ from any other OSGi service and can be used in the exact same way. To achieve fault tolerance, redundant instances of the service are distributed among several nodes. Each replica is given a special role, which is either active or passive. Active replica process service calls, passive replicas take their place in case they fail. How many replicas to use and what their specific role is can be configured according to the needs of any service. A proxy is used to consolidate service calls and relay them to the corresponding service instances. It analyzes every call and their result allowing the tolerance of hardware and software faults. The concept is designed to only use standardized OSGi interfaces and procedures. To identify the replicas of a service and what framework they are running on the RemoteServiceAdmin from the OSGi Enterprise Specification was used. It allows an imported service to be mapped to its origin. The described concept is available for free from the web server of the distributed systems lab of the Hochschule RheinMain.
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