A distributed system is defined as a collection of autonomous computers connected by a network, and with the appropriate distributed software for the system to be seen by users as a single entity capable of providing computing facilities. Distributed systems with centralised control have a distinguished control node, called leader node. The main role of a leader node is to distribute and manage shared resources in a resource-efficient manner. A distributed system with centralised control can use stream processing networks for communication. In a stream processing system, applications typically act as continuous queries, ingesting data continuously, analyzing and correlating the data, and generating a stream of results. Fault tolerance is the ability of a system to process the information, even if it happens any failure or anomaly in the system. Fault tolerance has become an important requirement for distributed systems, due to the possibility of failure has currently risen to the increase in number of nodes and the runtime of applications in distributed system. Therefore, to resolve this problem, it is important to add fault tolerance mechanisms order to provide the internal capacity to preserve the execution of the tasks despite the occurrence of faults. If the leader on a centralised control system fails, it is necessary to elect a new leader. While leader election has received a lot of attention in message-passing systems, very few solutions have been proposed for shared memory systems, as we propose. In addition, rollback-recovery strategies are important fault tolerance mechanisms for distributed systems, since that it is based on storing information into a stable storage in failure-free state and when a failure affects a node, the system uses the information stored to recover the state of the node before the failure appears. In this thesis, we are focused on creating two fault tolerance mechanisms for distributed systems with centralised control that uses stream processing for communication. These two mechanism created are leader election and log-based rollback-recovery, implemented using LPEL. The leader election method proposed is based on an atomic Compare-And-Swap (CAS) instruction, which is directly available on many processors. Our leader election method works with idle nodes, meaning that only the non-busy nodes compete to become the new leader while the busy nodes can continue with their tasks and later update their leader reference. Furthermore, this leader election method has short completion time and low space complexity. The log-based rollback-recovery method proposed for distributed systems with stream processing networks is a novel approach that is free from domino effect and does not generate orphan messages accomplishing the always-no-orphans consistency condition. Additionally, this approach has lower overhead impact into the system compared to other approaches, and it is a mechanism that provides scalability, because it is insensitive to the number of nodes in the system.

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Sammanfattning: Titel: ShoreLink - vägen tillbaka till förtroende: En fallstudie om förtroende och ledarskap inom logistiksektorn. Nivå: Examensarbete på Grundnivå (kandidatexamen) i ämnet företagsekonomi Författare: Therese Käck & Suzanna Svensson Atay Handledare: Emilia Kvarnström Datum: 2024 - maj Syfte: Studiens syfte är att utforska och öka förståelsen för, hur förändringar i ledarskap och insatser för att återskapa förtroende i relationerna mellan ledning och medarbetare på ShoreLink fungerat ur tjänstemännens och medarbetarnas perspektiv. Metod: Studien utgår från en kvalitativ forskningsansats där åtta semistrukturerade intervjuer genomfördes med ledning och medarbetare på ShoreLink. Insamlad empiri har därefter transkriberats för att sedan tematiskt analyseras. Resultat & slutsats: Studien visar hur ledningen genom fokus på relationer och en öppen, inbjudande kommunikation stärkt förtroendet mellan ledning och medarbetare, vilket kan ses i ett mer positivt arbetsklimat, ökat engagemang och ökad delaktighet hos medarbetarna. Helt återuppbyggt är förtroendet inte då det föreligger problematik gällande brister i arbetsmiljö, problem med avtal och ett felande system för tidrapportering och lön. Examensarbetets bidrag: Studien bidrar till ökad förståelse för hur förändringar i ledarskap påverkar medarbetarna och utvecklandet av förtroende. Likaså visar den vikten av att lösa alla grundläggande faktorer som påverkar medarbetarna för att kunna återställa förtroendet. Förslag till fortsatt forskning: Vidare forskning kan innebära utökade kvantitativa studier på samtliga ShoreLinks verksamhetsorter vilket kan öka förståelsen och mångfalden i perspektiven, samt få en utökad förståelse om den problematik, som kan ses i Luleå, återfinns i hela organisationen. Att undersöka skillnader och likheter mellan organisationer och branscher är viktigt för att utveckla riktlinjer som främjar förtroende och en positiv arbetskultur.

Software development is an area in which companies not only need to keep up with the latest technology, but they additionally need to continuously increase their productivity to stay competitive in the industry. One company currently facing these challenges is Storytel - one of the strongest players on the Swedish audiobook market - with about a fourth of all employees involved with software development, and a rapidly growing workforce. With the purpose of understanding how the Storytel Tech Department is performing, this thesis maps Storytel’s productivity defined through the Four Key Metrics - Deployment Frequency, Delivery Lead Time, Mean Time To Restore and Change Fail Rate. A classification is made into which performance category (Low, Medium, High, Elite) the Storytel Tech Department belongs to through a deep-dive into the raw system data existing at Storytel, mainly focusing on the case management system Jira. A survey of the Tech Department was conducted, to give insights into the connection between human and technical factors influencing productivity (categorized into Culture, Environment, and Process) and estimated productivity. Along with these data collections, interviews with Storytel employees were performed to gather further knowledge about the Tech Department, and to understand potential bottlenecks and obstacles. All Four Key Metrics could be determined based on raw system data, except the metric Mean Time To Restore which was complemented by survey estimates. The generalized findings of the Four Key Metrics conclude that Storytel can be minimally classified as a ‘medium’ performer. The factors, validated through factor analysis, found to have an impact on the Four Key Metrics were Generative Culture, Efficiency (Automation and Shared Responsibility) and Number of Projects. Lastly, the major bottlenecks found were related to Architecture, Automation, Time Fragmentation and Communication. The thesis contributes with interesting findings from an expanding, middle-sized, healthy company in the audiobook streaming industry - but the results can be beneficial for other software development companies to learn from as well. Performing a similar study with a greater sample size, and additionally enabling comparisons between teams, is suggested for future research.

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Cette recherche doctorale en histoire immédiate, s'inscrit dans une réflexion plus large sur l'étude de nouveaux conflits, la culture et l'emploi des forces armées françaises sur le terrain, en prenant l'exemple de son engagement en Afghanistan. Elle porte particulièrement sur l'emploi de l'arme du génie dont nous postulons à la grande importance de ses savoir-faire sur le terrain, en situation de contre-insurrection. / This doctoral research takes part on the study of the new conflicts, by taking the example of the French engineers in Afghanistan. We postulate for the big importance of these combat support units in situation of counterinsurgency.