Subhav Pradhan

A publish/subscribe middleware for dependable and real-time resource monitoring in the cloud

Providing scalable and QoS-enabled (i.e., real-time and reliable) monitoring of resources (both virtual and physical) in the cloud is essential to supporting application QoS properties in the cloud as well as identifying security threats. Existing approaches to resource monitoring in the cloud are based on web interfaces, such as RESTful APIs and SOAP, which cannot provide real-time information efficiently and scalably because of a lack of support for fine-grained and differentiated monitoring capabilities. Moreover, their implementation overhead results in a distinct loss in performance, incurs latency jitter, and degrades reliable delivery of time-sensitive information. To address these challenges this paper presents a novel lighter weight and scalable resource monitoring and dissemination solution based on the publish/subscribe (pub/sub) paradigm. Our solution called SQRT-C leverages the OMG Data Distribution Service (DDS) real-time pub/sub middleware, and uses effective software engineering principles to make it usable with multiple cloud platforms. Preliminary empirical results comparing SQRT-C with contemporary web-based resource usage monitoring services reveals that SQRT-C is significantly better than the conventional approaches in terms of latency, jitter and scalability.

CHARIOT: a domain specific language for extensible cyber-physical systems

Wider adoption, availability and ubiquity of wireless networking technologies, integrated sensors, actuators, and edge computing devices is facilitating a paradigm shift by allowing us to transition from traditional statically configured vertical silos of Cyber-Physical Systems (CPS) to next generation CPS that are more open, dynamic and extensible. Fractionated spacecraft, smart cities computing architectures, Unmanned Aerial Vehicle (UAV) clusters are all examples of extensible CPS wherein extensibility is implied by the dynamic aggregation of physical resources, affect of physical dynamics on availability of computing resources, and various multi-domain applications hosted on these systems. However, realization of extensible CPS requires resolving design-time and runtime challenges emanating from properties specific to these systems. In this paper, we first describe different properties of extensible CPS - dynamism, extensibility, remote deployment, security, heterogeneity and resilience. Then we identify different design-time challenges stemming from heterogeneity and resilience requirements. We particularly focus on software heterogeneity arising from availability of various communication middleware. We then present appropriate solutions in the context of a novel domain specific language and describe how this language and its features have evolved from our past work.

Towards Reliability-Based Decision Making in Cyber-Physical Systems

Cyber-physical systems (CPS) are systems with a tight integration between the computational (also referred to as software or cyber) and physical (hardware) components. While the reliability evaluation of physical systems is well-understood and well-studied, reliability evaluation of CPS is difficult because software systems do not degrade and follow a well-defined failure model like physical systems. In this paper, we propose a framework for formulating the CPS reliability evaluation as a dependence problem derived from the software component dependences, functional requirements and physical system dependences. We also consider sensor failures, and propose a method for estimating software failures in terms of associated hardware and software inputs. This framework is codified in a domain-specific modeling language, where every system-level function is mapped to a set of required components using functional decomposition and function-component association; this provides details about operational constraints and dependences. We also illustrate how the encoded information can be used to make reconfiguration decisions at runtime. The proposed methodology is demonstrated using a smart parking system, which provides localization and guidance for parking within indoor environments.

Achieving resilience in distributed software systems via self-reconfiguration

We describe resilient operation of cyber-physical application platforms.We describe implicit design-time encoding of the reconfiguration.We describe design-time analysis and validation tools for these systems. Improvements in mobile networking combined with the ubiquitous availability and adoption of low-cost development boards have enabled the vision of mobile platforms of Cyber-Physical Systems (CPS), such as fractionated spacecraft and UAV swarms. Computation and communication resources, sensors, and actuators that are shared among different applications characterize these systems. The cyber-physical nature of these systems means that physical environments can affect both the resource availability and software applications that depend on resource availability. While many application development and management challenges associated with such systems have been described in existing literature, resilient operation and execution have received less attention. This paper describes our work on improving runtime support for resilience in mobile CPS, with a special focus on our runtime infrastructure that provides autonomous resilience via self-reconfiguration. We also describe the interplay between this runtime infrastructure and our design-time tools, as the later is used to statically determine the resilience properties of the former. Finally, we present a use case study to demonstrate and evaluate our design-time resilience analysis and runtime self-reconfiguration infrastructure.

Real-time fault tolerant deployment and configuration framework for cyber physical systems

This paper describes ongoing work on making the deployment and configuration functionality for cyber physical systems reliable and tolerant to failures, while also supporting predictable and incremental online redeployment and reconfiguration of application functionality. Our work is currently designed and evaluated in the context of a system of fractionated spacecrafts, which is a representative CPS system.

Towards a generic computation model for smart city platforms

Smart emergency response systems, smart transportation systems, smart parking spaces are some examples of multi-domain smart city systems that require large-scale, open platforms for integration and execution. These platforms illustrate high degree of heterogeneity. In this paper, we focus on software heterogeneity arising from different types of applications. The source of variability among applications stems from (a) timing requirements, (b) rate and volume of data they interact with, and (c) behavior depending on whether they are stateful or stateless. These variations result in applications with different computation models. However, a smart city system can comprise multi-domain applications with different types and therefore computation models. As such, a key challenge that arises is that of integration; we require some mechanism to facilitate integration and interaction between applications that use different computation models. In this paper, we first identify computation models based on different application types. Second, we present a generic computation model and explain how it can map to previously identified computation models. Finally, we briefly describe how the generic computation model fits in our overall smart city platform architecture.

Resilience at the edge in cyber-physical systems

As the number of low cost computing devices at the edge of communication network increase, there are greater opportunities to enable innovative capabilities, especially in cyber-physical systems. For example, micro-grid power systems can make use of computing capabilities at the edge of a Smart Grid to provide more robust and decentralized control. However, the downside to distributing intelligence to the edge away from the controlled environment of the data centers is the increased risk of failures. The paper introduces a framework for handling these challenges. The contribution of this framework is to support strategies to (a) tolerate the transient faults as they appear due to network fluctuations or node failures, and to (b) systematically reconfigure the application if the faults persist.

Towards a resilient deployment and configuration infrastructure for fractionated spacecraft

Fractionated spacecraft are clusters of small, independent modules that interact wirelessly to realize the functionality of a traditional monolithic spacecraft. System F6 (F6 stands for Future, Fast, Flexible, Fractionated, Free-Flying spacecraft) is a DARPA program for fractionated spacecraft. Software applications in F6 are implemented in the context of the F6 Information Architecture Platform (IAP), which provides component-based abstractions for composing distributed applications. The lifecycle of these distributed applications must be managed autonomously by a deployment and configuration (D&C) infrastructure, which can redeploy and reconfigure the running applications in response to faults and other anomalies that may occur during system operation. Addressing these D&C requirements is hard due to the significant fluctuation in resource availabilities, constraints on resources, and safety and security concerns. This paper presents the key architectural ideas that are required in realizing such a D&C infrastructure.

Designing a Resilient Deployment and Reconfiguration Infrastructure for Remotely Managed Cyber-Physical Systems

Multi-module Cyber-Physical Systems (CPS), such as satellite clusters, swarms of Unmanned Aerial Vehicles (UAV), and fleets of Unmanned Underwater Vehicles (UUV) provide a CPS cluster-as-a-service for CPS applications. The distributed and remote nature of these systems often necessitates the use of Deployment and Configuration (D&C) services to manage the lifecycle of these applications. Fluctuating resources, volatile cluster membership and changing environmental conditions necessitate resilience. Thus, the D&C infrastructure does not only have to undertake basic management actions, such as activation of new applications and deactivation of existing applications, but also has to autonomously reconfigure existing applications to mitigate failures including D&C infrastructure failures. This paper describes the design and architectural considerations to realize such a D&C infrastructure for component-based distributed systems. Experimental results demonstrating the autonomous resilience capabilities are presented.

Poster Abstract: A Distributed and Resilient Platform for City-Scale Smart Systems

The advent of the Internet of Things (IoT) is driving several technological trends. The first trend is an increased level of integration between edge devices and commodity computers. This trend, in conjunction with low power-devices, energy harvesting, and improved battery technology, is enabling the next generation of information technology (IT) innovation: city-scale smart systems. These types of IoT systems can operate at multiple time-scales, ranging from closed-loop control requiring strict real-time decision and actuation to near real-time operation with humans-in-the-loop, as well as to long-term analysis, planning, and decision-making.