Dominik Meißner

Abstract: State changes over time are inherent characteristics of stateful applications. So far, there are almost no attempts to make the past application history programmatically accessible or even modifiable. This is primarily due to the complexity of temporal changes and a difficult alignment with prevalent programming primitives and persistence strategies. Retroactive computing enables powerful capabilities though, including computations and predictions of alternate application timelines, post-hoc bug fixes, or retroactive state explorations. We propose an event-driven programming model that is oriented towards serverless computing and applies retroaction to the event sourcing paradigm. Our model is deliberately restrictive, but therefore keeps the complexity of retroactive operations in check. We then introduce retro-λ, a runtime platform that implements the model and provides retroactive capabilites to its applications. While retro-λ only shows negligible performance overheads compared to similar solutions for running regular applications, it enables its users to execute retroactive computations on the application histories as part of its programming model.

Abstract: Event sourcing is increasingly used and implemented in event-based systems for maintaining the evolution of application state. However, unbounded event logs are impracticable for many systems, as it is difficult to align scalability requirements and long-term runtime behavior with the corresponding storage requirements. To this end, we explore the design space of log pruning approaches suitable for event-sourced systems. Furthermore, we survey specific log pruning mechanisms for event-sourced logs. In a brief evaluation, we point out the trade-offs when applying pruning to event logs and highlight the applicability of log pruning to event-sourced systems.

Abstract: Several data-intensive applications take streams of events as a continuous input and internally map events onto a dynamic, graph-based data model which is then used for processing. The differences between event processing, graph computing, as well as batch processing and near-realtime processing yield a number of specific requirements for computing platforms that try to unify theses approaches. By combining an altered actor model, an event-sourced persistence layer, and a vertex-based, asynchronous programming model, we propose a distributed computing platform that supports event-driven, graph-based applications in a single platform. Our Chronograph platform concept enables online and offline computations on event-driven, history-aware graphs and supports different processing models on the evolving graph.

Abstract: In large-scale disaster scenarios, efficient triage management is a major challenge for emergency services. Rescue forces traditionally respond to such incidents with a paper-based triage system, but technical solutions can potentially achieve improved usability and data availability. We develop a triage management system based on commodity hardware and software components to verify this claim. We use a single-hop, ad-hoc network architecture with multi-master replication, a tablet-based device setup and a mobile application for emergency services. We study our system in cooperation with regional emergency services and describe experiences from a field exercise. We show that state-of-the-art commodity technology provides the means necessary to implement a triage management system compatible with existing emergency service procedures, while introducing additional benefits. This work highlights that powerful real-world ad-hoc networking applications do not require unreasonable development effort, as existing tools from distributed systems, like replicating No-SQL databases, can be used successfully.

Tags: PROJEKT, AA, BA, MA, FrankKargl, retroaction, distributed, DominikMeissner

Abstract: Retroactive computing enables programmatical access to the history of an application. This offers a variety of capabilities, such as computations and predictions of alternate application timelines, post-hoc bug fixes, and retroactive state explorations. Reads and writes of the application state have to be tracked and persisted in order to support retroaction. This is fairly simple for a single-writer append-only log, but entails various issues in a distributed setting. This thesis/project should explore different approaches for a distributed dependency tracking, including a prototypical implementation based on an existing platform prototype and an evaluation of the resulting artifacts.

Tags: PROJEKT, AA, BA, BenjaminErb, FrankKargl, sidgraph, distributed, DominikMeissner

Abstract: Event sourcing is an alternative persistence approach that maintains a log of state-changing events instead of altering states directly. Event-sourced architectures require an event store for efficiently appending and retrieving log entries. In this project, an evaluation of different key/value stores and alternative (No)SQL stores is to be conducted in order to identify stores appropriate for event sourcing.

Tags: PROJEKT, AA, BA, BenjaminErb, FrankKargl, sidgraph, distributed, DominikMeissner

Abstract: As part of an ongoing research project at our institute, we are currently developing a novel distributed computing platform prototype. The systems provides a graph-based, asynchronous programming model and takes advantage of event sourcing for history-aware computations. The aim of this student work is the identification and evaluation of appropriate secondary index structures, in order to provide fast access onto specific notes of the graph topology. Also, a prototypical implementation is part of this work.

Tags: PROJEKT, AA, BA, MA, FrankKargl, retroaction, distributed, DominikMeissner

Abstract: Retroactive computing enables programmatical access to the history of an application. This offers a variety of capabilities, such as computations and predictions of alternate application timelines, post-hoc bug fixes, and retroactive state explorations. Reads and writes of the application state have to be tracked and persisted in order to support retroaction. This is fairly simple for a single-writer append-only log, but entails various issues in a distributed setting. This thesis/project should explore different approaches for a distributed dependency tracking, including a prototypical implementation based on an existing platform prototype and an evaluation of the resulting artifacts.

Tags: PROJEKT, AA, BA, BenjaminErb, FrankKargl, sidgraph, distributed, DominikMeissner

Abstract: Event sourcing is an alternative persistence approach that maintains a log of state-changing events instead of altering states directly. Event-sourced architectures require an event store for efficiently appending and retrieving log entries. In this project, an evaluation of different key/value stores and alternative (No)SQL stores is to be conducted in order to identify stores appropriate for event sourcing.

Tags: PROJEKT, AA, BA, BenjaminErb, FrankKargl, sidgraph, distributed, DominikMeissner

Abstract: As part of an ongoing research project at our institute, we are currently developing a novel distributed computing platform prototype. The systems provides a graph-based, asynchronous programming model and takes advantage of event sourcing for history-aware computations. The aim of this student work is the identification and evaluation of appropriate secondary index structures, in order to provide fast access onto specific notes of the graph topology. Also, a prototypical implementation is part of this work.