This book provides an in-depth description of event-based systems, covering topics ranging from local event matching and distributed event forwarding algorithms, through a practical discussion of software engineering issues raised by the event-based style, to state-of-the-art research in event-based systems like composite event detection and security. The authors offer a comprehensive overview, and show the power of event-based architectures in modern system design, encouraging professionals to exploit this technique in next generation large-scale distributed applications like information dissemination, network monitoring, enterprise application integration, or mobile systems.

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Distributed event-based systems

The fast increment in the number of IoT (Internet of Things) devices is accelerating the research on new solutions to make cloud services scalable. In this context, the novel concept of fog computing as well as the combined fog-to-cloud computing paradigm is becoming essential to decentralize the cloud, while bringing the services closer to the end-system. This article surveys e application layer communication protocols to fulfill the IoT communication requirements, and their potential for implementation in fog- and cloud-based IoT systems. To this end, the article first briefly presents potential protocol candidates, including request-reply and publish-subscribe protocols. After that, the article surveys these protocols based on their main characteristics, as well as the main performance issues, including latency, energy consumption, and network throughput. These findings are thereafter used to place the protocols in each segment of the system (IoT, fog, cloud), and thus opens up the discussion on their choice, interoperability, and wider system integration. The survey is expected to be useful to system architects and protocol designers when choosing the communication protocols in an integrated IoT-to-fog-to-cloud system architecture.

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A Survey of Communication Protocols for Internet of Things and Related Challenges of Fog and Cloud Computing Integration

It is believed that transactions belong to key services of componentbased middleware. However, surprisingly, there is no general agreement on how the component-based middleware support for transactions should look like. In this paper we exploit our experiences with Jironde [4], a flexible framework that extends the Fractal component model [1, 2] with transactions via a set of transactional controllers that manage transactions on behalf of a component. Then we identify several key architectural and technical issues related to enhancing component-based middleware with transactions. We investigate how current technologies address theses issues, and the suitability of current standards to support transaction processing in component-based middleware. 1 Transactions and Components: Architectural Issues Different component models deal with component’s participation in a transaction differently. In the explicit transaction participation, the scenario of involving a component C to a transaction t essentially consists of the three steps as follows: 1) C is registered to t. 2) A client invokes various operations on C. 3) At the time of t’s validation, the transaction manager invokes specific methods of the registered C’s interfaces. These (callback) methods must be implemented by the transactional components. With the implicit transaction participation, components are not obliged to implement any functionality related to transactions. Any time C is visited by a transaction t, the transaction manager of the container keeps all necessary information to manage atomicity, concurrency control, and recovery. Different component standards deal with component participation in transactions differently. CCM use the explicit transaction participation, COM+ uses the implicit one, while EJB mix both. Component-unaware transactions manipulate data without any knowledge on whether they are organized or related to components. For component-aware transactions, components are the data they manipulate with. We believe that all the CCM, EJB, and COM+ transactions are component-unaware. A component is transaction-unaware if its code does not use any transactional primitives and is not therefore in any way dependent on any transactional standard, while a transactionaware component is the opposite. Component’s awareness of transactions reflects the implicit/explicit transaction participation but includes also some hidden expectations of the component design. Transaction-unaware container does not deal with On Enhancing Component-Based Middleware with Transactions 2 transactions, which are managed at the application level instead. Transaction-aware container provides some transaction management features, such as containerdemarcation, transaction propagation, concurrency control, etc. EJB, CCM and COM+ are examples that provide such containers. 2 Transactions and Components: Technical Issues The technical issues related to transactional component include concurrency control, recovery, and transaction context propagation. As for concurrency control, the current technologies either use a simple read/write model or do not allow any concurrent access to component instances at all. It would be beneficial to exploit the concurrency potential of components by e.g. the use of conflict matrixes defined on all the methods of all implemented interfaces. Both concurrency control and recovery of components reflect the architectural patterns presented in the previous section. Another important issue is the transaction context propagation. There are several options of how to specify a transaction propagation policy, as well as whether to define it either during the component’s development or during its deployment. A last issue is to support the definition of new propagation policies, like JOTDF [5] does.

On The Move to meaningful Internet systems 2003 : OTM 2003 Workshops : OTM Confederated International Workshops : HCI-SWWA, IPW, JTRES, WORM, WMS, and WRSM 2003, Catania, Sicily, Italy, November 3-7, 2003 : proceedings

The fast increment in the number of IoT (Internet of Things) devices is accelerating the research on new solutions to make cloud services scalable. In this context, the novel concept of fog computing as well as the combined fog-to-cloud computing paradigm is becoming essential to decentralize the cloud, while bringing the services closer to the end-system. This paper surveys on the application layer communication protocols to fulfil the IoT communication requirements, and their potential for implementation in fog- and cloud-based IoT systems. To this end, the paper first presents a comparative analysis of the main characteristics of IoT communication protocols, including request-reply and publish-subscribe protocols. After that, the paper surveys the protocols that are widely adopted and implemented in each segment of the system (IoT, fog, cloud), and thus opens up the discussion on their interoperability and wider system integration. Finally, the paper reviews the main performance issues, including latency, energy consumption and network throughput. The survey is expected to be useful to system architects and protocol designers when choosing the communication protocols in an integrated IoT-to-fog-to-cloud system architecture.

/pdf/survey-of-communication-protocols-for-internet-of-things-and-1348ztzxhj.pdf

Survey of Communication Protocols for Internet-of-Things and Related Challenges of Fog and Cloud Computing Integration

Message oriented middleware (MOM) refers to the software infrastructure supporting sending and receiving messages between distributed systems. AMQP and MQTT are the two most relevant protocols in this context. They are extensively used for exchanging messages since they provide an abstraction of the different participating system entities, alleviating their coordination and simplifying the communication programming details. These protocols, however, have not been thoroughly tested in the context of mobile or dynamic networks like vehicular networks. In this paper we present an experimental evaluation of both protocols in such scenarios, characterizing their behavior in terms of message loss, latency, jitter and saturation boundary values. Based on the results obtained, we provide criteria of applicability of these protocols, and we assess their performance and viability. This evaluation is of interest for the upcoming applications of MOM, especially to systems related to the Internet of Things.

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A comparative evaluation of AMQP and MQTT protocols over unstable and mobile networks

Modeling and execution of event stream processing in business processes

Modern pub/sub systems perform message routing based on the message content and allow subscribers to receive messages related to their subscriptions and the current context. Both content and context encode sensitive information which should be protected from third-party brokers that make routing decisions. In this work, we address this issue by proposing an approach that assures the confidentiality of the messages being published and subscriptions being issued while allowing the brokers to make routing decisions without decrypting individual messages and subscriptions, and without learning the context. Further, subscribers with a frequently changing context, such as location, are able to issue and update subscriptions without revealing the subscriptions in plaintext to the broker and without the need to contact a trusted third party for each subscription change resulting from a change in the context. Our approach is based on a modified version of the Paillier additive homomorphic cryptosystem and a novel group key management scheme. The former construct is used to perform privacy preserving matching, and the latter construct is used to enforce fine-grained encryption-based access control on the messages being published. We optimize our approach in order to efficiently handle frequently changing contexts. We have implemented our approach in a prototype using an industry strength JMS broker middleware. The experimental results show that our approach is highly practical.

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Privacy Preserving Context Aware Publish Subscribe Systems

The Internet of Things and Cyber-physical Systems provide enormous amounts of real-time data in form of streams of events Businesses can benefit from the integration of this real-world data; new services can be provided to customers, or existing business processes can be improved Events are a well-known concept in business processes However, there is no appropriate abstraction mechanism to encapsulate event stream processing in units that represent business functions in a coherent manner across the process modeling, process execution, and IT infrastructure layer In this paper we present Event Stream Processing Units (SPUs) as such an abstraction mechanism SPUs encapsulate application logic for event stream processing and enable a seamless transition between process models, executable process representations, and components at the IT layer We derive requirements for SPUs and introduce a BPMN extension to model SPUs We present a runtime infrastructure that executes SPUs and supports implicit invocation and completion semantics We illustrate our approach using a logistics process as running example

/pdf/event-stream-processing-units-in-business-processes-3zwtcagd7p.pdf

Event stream processing units in business processes

Publish/subscribe-based messaging systems are used increasingly often as a communication mechanism in data-oriented web applications. Such applications often pose serious performance and scalability challenges. To address these challenges, it is important that systems are tested using benchmarks to evaluate their performance and scalability before they are put into production. In this paper, we present jms2009-PS, a new benchmark for publish/subscribe-based messaging systems built on top of the SPECjms2007 standard workload.We introduce the benchmark and discuss its configuration parameters showing how the workload can be customized to evaluate various aspects of publish/subscribe communication. Finally, we present a case study illustrating how the benchmark can be used for performance analysis of messaging servers.

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Benchmarking publish/subscribe-based messaging systems

With the increasing importance of event-based systems the performance of underlying event transporting systems, such as message oriented middleware (MOM), becomes business critical. Therefore, we see a strong need for benchmarks for such environments. Several messaging standards and protocols for middleware exist; most popular is the Java Message Service (JMS) which is defining an API rather than a wire protocol. An emerging standard is the new wire level protocol Advanced Message Queuing Protocol (AMQP). It originated in the financial sector and is developed by a consortium of over 20 member organizations.

/pdf/towards-benchmarking-of-amqp-1y2fox5udm.pdf

Stefan Appel

Papers

Modeling and execution of event stream processing in business processes

Privacy Preserving Context Aware Publish Subscribe Systems

Event stream processing units in business processes

Benchmarking publish/subscribe-based messaging systems

Towards benchmarking of AMQP