An important step in the development of dependable systems is the validation of their fault tolerance properties. Fault injection has been widely used for this purpose, however with the rapid increase in processor complexity, traditional techniques are also increasingly more difficult to apply. This paper presents a new software implemented fault injection and monitoring environment, called Xception, which is targeted for the modern and complex processors. Xception uses the advanced debugging and performance monitoring features existing in most of the modern processors to inject quite realistic faults by software, and to monitor the activation of the faults and their impact on the target system behavior in detail. Faults are injected with minimum interference with the target application. The target application is not modified, no software traps are inserted, and it is not necessary to execute the target application in special trace mode (the application is executed at full speed). Xception provides a comprehensive set of fault triggers, including spatial and temporal fault triggers, and triggers related to the manipulation of data in memory. Faults injected by Xception can affect any process running on the target system (including the kernel), and it is possible to inject faults in applications for which the source code is not available. Experimental results are presented to demonstrate the accuracy and potential of Xception in the evaluation of the dependability properties of the complex computer systems available nowadays.

The evolution that serverless computing represents, the economic forces that shape it, why it could fail, and how it might fulfill its potential.

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This paper addresses the problem of injection of faults in the communication system of disjoint menuuy parallel computers and presents .fuult injection resultsshowing that 5% to 3Wo of the fuults injected in the conzmunication subsystem of a commercial purullel computer caused undetected errors thut l e d the upplicution to generate erroneous results. All these C U .~ correspond to situations in which it would be virtuidly inzpossible to detect that the benchmark output wus erroneous, us the size of the results file wus pluusible and no system errors h d been detected. This emphasises the n e d for .fuult tolerant techniques in parallel systems in order to uchieve confidence in the application results. This is especially true in massively parallel computers, us the probability of occurring faults increase with the number of processing nodes. Moreover, in disjoint memory computers, which is the most popular and scaluble parallel architecture, the conzmunication subsystem plays an importunt role, and is also very prone to errors. CSFI (Conznzunicution Sofiwure Fuult Injector) is a versutile tool to inject conznzunicution ,fiiults in purallel computers. Fuults injecttd with CSFI directly emulate communication faults und spurious messuges generated by non fail-silent nodes by sojbvur-e, allowing the evaluation of the impact of.fuults in purullel system, urd the assessment of fault tolerant techniques. The use o f CSFI is nearly trunspurent to the target upplicution us it only requires minor uduptutions. Deterministic ,fuults o f different nuture can be injected without user intervention and fuult injection results ure collectd uutonzuticully by CSFI.