Baliś, Bartosz
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Item type:Article, Access status: Open Access , Automatic proxy generation and load-balancing-based dynamic choice of services(Wydawnictwa AGH, 2012) Dąbrowski, Jarosław; Feduniak, Sebastian; Baliś, Bartosz; Bartyński, Tomasz; Funika, WłodzimierzThe paper addresses the issues of invoking services from within workflows which are becoming an increasingly popular paradigm of distributed programming. The main idea of our research is to develop a facility which enables load balancing between the available services and their instances. The system consists of three main modules: a proxy generator for a specific service according to its interface type, a proxy that redirects requests to a concrete instance of the service and load-balancer (LB) to choose the least loaded virtual machine (VM) which hosts a single service instance. The proxy generator was implemented as a bean (in compliance to EJB standard) which generates proxy according to the WSDL service interface description using XSLT engine and then deploys it on a GlassFish application server using GlassFish API, the proxy is a BPEL module and load-balancer is a stateful Web Service.Item type:Article, Access status: Open Access , Database replication for disconnected operations with quasi real-time synchronization(Wydawnictwa AGH, 2023) Mucha, Rafał; Baliś, Bartosz; Grigoras, Costin; Kitowski, JacekDatabase replication is a way to improve system throughput or achieve high availability. In most cases, the use of an active-active replica architecture is efficient and easy to deploy. Such a system has CP properties (from the CAP theorem: consistency, availability, and network-partition tolerance). Creating an AP (available and partition-tolerant) system requires the use of multi-primary replication. Because of the many difficulties in its implementation, this approach is not widely used, however, ALICE’s deployment of CCDB (experiment conditions and calibration database) needs to be an AP system in two locations. This necessity became the inspiration for examining the state-of-the-art methods in this field and testing the available solutions. The tests that were performed evaluated the performance of the chosen replication tools: Bucardo, and EDB Replication Server, these showed that the tested tools could be successfully used for the continuous synchronization of two independent database instances.Item type:Doctoral Dissertation, Access status: Open Access , Monitoring of grid scientific workflows(Data obrony: 2009) Baliś, Bartosz
Wydział Elektrotechniki, Automatyki, Informatyki i ElektronikiGrid scientific workflows are a means of defining in silico experiments in modern infrastructures for e-Science. Monitoring of Grid scientific workflows poses specific challenges due to the dynamicity of the Grid, and the diversity of scenarios where monitoring is important. The main contribution of this dissertation is the identification and analysis of key challenges in monitoring of Grid scientific workflows, elaboration of solutions to those challenges, and validation of those solutions. Four areas where key issues arise are recognized: building an infrastructure for Grid scientific workflows, solving the problem of on-line monitoring support within this infrastructure, monitoring of workflow legacy backends, and development of an information model for recording workflow executions. The results of the research are validated using diverse methodologies. Prototypes of the designed software components were built and used for monitoring of real-life workflows within EU-IST projects. Model-based approach using Queuing Networks and a discrete-event simulation has also been used to validate the performance characteristics of the proposed solutions.