Reliable scientific service compositions

Abstract. Distributed service oriented architectures (SOAs) are increas-ingly used by users, who are insufficiently skilled in the art of distributed system programming. A good example are computational scientists who build large-scale distributed systems using service-oriented Grid comput-ing infrastructures. Computational scientists use these infrastructure to build scientific applications, which are composed from basic Web ser-vices into larger orchestrations using workflow languages, such as the Business Process Execution Language. For these users reliability of the infrastructure is of significant importance and that has to be provided in the presence of hardware or operational failures. The primitives avail-able to achieve such reliability currently leave much to be desired by users who do not necessarily have a strong education in distributed sys-tem construction. We characterise scientific service compositions and the environment they operate in by introducing the notion of global scien-tific BPEL workflows. We outline the threats to the reliability of such workflows and discuss the limited support that available specifications and mechanisms provide to achieve reliability. Furthermore, we propose a line of research to address the identified issues by investigating auto-nomic mechanisms that assist computational scientists in building, exe-cuting and maintaining reliable workflows.

Technical Challenges of Microservices Migration

The microservices architecture is a recent trend in the software engineering community, with the number of research articles in the field increasing, and more companies adopting the architectural style every year. However, the migration of a monolith to the microservices architecture is an error-prone process with a lack of guidelines for its execution. Also, microservices introduce a lot of different challenges that are not faced when following a monolithic architecture. This work aims to fill some gaps in current microservices research by providing a catalogue of the currently most common challenges of adopting this architectural style, and possible solutions for them. For this reason, a systematic mapping study was executed analysing 54 different articles. Also, 30 industry professionals participated in a questionnaire regarding the topic. Furthermore, a participant observation experiment was performed to retrieve additional industry data. Moreover, one of the identified challenges – distributed transactions management – was further detailed and a solution implemented using the choreographed saga pattern. The solution is publicly available as an open-source project. Finally, multiple experts in the microservices field validated the results of the research and the distributed transactions solution and provided insights regarding the value of this work.A arquitetura de microserviços é uma tendência recente na comunidade de engenharia de software, com o número de artigos publicados sobre o tema a aumentar, assim como o número de empresas a adoptar o estilo arquitetural todos os anos. No entanto, o processo de migração de um monolito para uma arquitetura orientada a microserviços tem um alto potencial de erros, uma vez que existe falta de orientações sobre como conduzir o processo corretamente. Para além disso, os microserviços introduzem muitos desafios diferentes que não são enfrentados no desenvolvimento de um sistema monolitico. Este trabalho pretende preencher algumas destas lacunas na investigação da arquitetura de microserviços através da construção de um catalogo dos principais desafios enfrentados ao adoptar o estilo arquitetural e soluções possíveis para estes. Por este motivo, um systematic mapping study foi desenvolvido, analisando 54 artigos diferentes. Para além disso, 30 profissionais da industria responderam a questionario sobre o tema. Finalmente, para obter dados adicionais da indústria, uma experiência de migração foi realizada e observada de forma ativa. Ainda, um dos desafios identificados – gestão de transações distribuídas – foi detalhado e uma solução implementada usando o padrão de sagas coreografadas. A solução está publicamente disponível como um projecto open-source. Finalmente, vários peritos em microserviços avaliaram os resultados deste trabalho, incluindo a solução desenvolvida para gestão de transações distribuídas, e deram feedback relativamente ao valor deste trabalho

ReLock: a resilient two-phase locking RESTful transaction model

Service composition and supporting transactions across composed services are among the major challenges characterizing service-oriented computing. REpresentational State Transfer (REST) is one of the approaches used for implementing Web services that is gaining momentum thanks to its features making it suitable for cloud computing and microservices-based contexts. This paper introduces ReLock, a resilient RESTful transaction model introducing general purpose transactions on RESTful services by a layered approach and a two-phase locking mechanism not requesting any change to the RESTful services involved in a transaction

La Permuta: an effective instrument for housing transactions in Cuba

This paper is about the permuta, which is the only legal instrument created by the Cuban authorities to facilitate land and housing exchanges. Beyond that fact, the permuta has sociological and economical significance as being the escape valve for the people in their resistance to being standard people in standard housing,i as it reflects the increasing demand of families for more diversified dwelling options. In the absence of a formal real estate market, the permuta has proved very effective in incorporating hidden and informal valuations and transactions in housing, where monetary interests are increasingly appearing as an important feature. Over the last decades, the number of arrangements and agreements between the parties, and the complexity of the negotiations has increased. The transactions within the permuta now incorporate new aspects that anticipate future value increments and other benefits and profits from the development of home based businesses, or that anticipate positive impacts derived from public investments or new urban regulations. The study of the permuta is therefore very attractive for urban planners and economists. But the study is also difficult for various reasons: it is very vulnerable to legal and institutional changes, it has a dual (legal and illegal) connotation, it has a large capacity to mutate and camouflage in order to evade restrictions, and there are no trustworthy records of the informal transactions

Towards an Enhanced Protocol for Improving Transactional Support in Interoperable Service Oriented Application-Based (SOA-Based) Systems

When using a shared database for distributed transactions, it is often difficult to connect business processes and softwarecomponents running on disparate platforms into a single transaction. For instance, one platform may add or update data, and thenanother platform later access the changed or added data. This severely limits transactional capabilities across platforms. Thissituation becomes more acute when concurrent transactions with interleaving operations spans across different applications andresources. Addressing this problem in an open, dynamic and distributed environment of web services poses special challenges,and still remains an open issue. Following the broad adoption and use of the standard Web Services Transaction Protocols,requirements have grown for the addition of extended protocols to handle problems that exist within the context of interoperableservice-oriented applications. Most extensions to the current standard WS-Transaction Protocols still lack proper mechanisms forerror-handling, concurrency control, transaction recovery, consolidation of multiple transaction calls into a single call, and securereporting and tracing for suspicious activities. In this research, we will first extend the current standard WS-TransactionFramework, and then propose an enhanced protocol (that can be deployed within the extended framework) to improvetransactional and security support for asynchronous applications in a distributed environment. A hybrid methodology whichincorporates service-oriented engineering and rapid application development will be used to develop a procurement system(which represents an interoperable service-oriented application) that integrates our proposed protocol. We will empiricallyevaluate and compare the performance of the enhanced protocol with other conventional distributed protocols (such as 2PL) interms of QoS parameters (throughput, response time, and resource utilization), availability of the application, databaseconsistency, and effect of locking on latency, among other factors.Keywords: Database, interoperability, security, concurrent transaction, web services, protocol, service-oriente

Viitearkkitehtuuri tapahtumapohjaiselle mikropalveluarkkitehtuurille pilvipalveluissa

The emergence of public cloud computing platforms has had a profound effect on how software is being developed. To take advantage of many of the features of cloud platforms, software architecture of applications must aligned with the characteristics of cloud services. Where systems designed for traditional data center deployments have typically consisted of a single large application and a centralized data store, systems targeting cloud platform have become distributed applications. The microservice architecture is a software architecture style for building distributed systems that consist of autonomous services, each responsible for a single problem domain. Decomposing an application to individual components makes is possible to utilize cloud platform features such as scaling each part of the system according to load and performance. Enterprise applications are the context where the microservice architecture pattern is typically applied. These applications are large, long-lived, in state of constant change and highly integrated to other systems. But building complex enterprise applications as distributed systems poses architectural challenges on how to build a system that is evolvable, maintainable and understandable. This thesis describes patterns for building microservice systems that can scale to a large amount of services while retaining the autonomy the services and the maintainability of the system as a whole. A key factor in these patterns is the use of events for communication between the different components of the system. The thesis then presents a reference architecture on how such a system can be developed by utilizing managed services of a public cloud platform.Lisääntyvä pilvipalveluiden käyttö on vaikuttanut merkittävästi siihen, millaisia sovelluksia kehitetään. Sovelluksen arkkitehtuurin täytyy olla suunniteltu siten, että pilvipalveluiden ominaisuuksia voidaan hyödyntää. Sovellukset, jotka ovat suunniteltu ennen pilvipohjaisia arkkitehtuureja koostuvat tyypillisesti yhdestä suuresta asennettavasta komponentista ja keskitetystä tietovarastosta. Pilvipalveluiden myötä tämän mallin sijaan on ruvettu rakentamaan hajautettuja järjestelmiä. Mikropalveluarkkitehtuuri on ohjelmistoarkkitehtuuri, jossa hajautettu järjestelmä koostetaan yksittäisistä erillisistä palveluista. Jokainen palvelu vastaa järjestelmän tietystä toiminnosta tai osa-alueesta. Arkkitehtuuri, jossa sovellus on pilkottu pieniin autonomisiin komponentteihin mahdollistaa monien pilvipalveluiden ominaisuuksien (kuten kuorman mukaisen skaalauksen) käytn. Monimutkaiset yritysjärjestelmät ovat kenttä, jossa mikropalveluarkkitehtuuria tyypillisesti käytetään. Nämä järjestelmät ovat suuria, jatkuvan muutoksen alaisia ja moninaisin tavoin integroituneita useisiin muihin järjestelmiin. Monimutkaisten yritysjärjestelmien rakentaminen mikropalveluarkkitehtuurilla luo omat haasteensa siinä, miten järjestelmästä saadaan ylläpidettävä, jatkokehityskelpoinen ja ymmärrettävä. Tämä diplomityö kuvaa malleja mikropalvelujärjestelmien rakentamiseen siten, että järjestelmän kasvaessa yksittäiset mikropalvelut pysyvät erillisinä ja autonomisina sekä järjestelmä kokonaisuutena pystyy ylläpidettävänä. Avainrakenne näiden tavoitteiden saavuttamisessa on tapahtumien käyttö tiedon välittämisessä palveluiden välillä. Diplomityössä esitetään sitten viitearkkitehtuuri miten nämä mallit voidaan ottaa käyttöön julkisessa pilvipalvelussa

Improving the Scalability of DPWS-Based Networked Infrastructures

The Devices Profile for Web Services (DPWS) specification enables seamless discovery, configuration, and interoperability of networked devices in various settings, ranging from home automation and multimedia to manufacturing equipment and data centers. Unfortunately, the sheer simplicity of event notification mechanisms that makes it fit for resource-constrained devices, makes it hard to scale to large infrastructures with more stringent dependability requirements, ironically, where self-configuration would be most useful. In this report, we address this challenge with a proposal to integrate gossip-based dissemination in DPWS, thus maintaining compatibility with original assumptions of the specification, and avoiding a centralized configuration server or custom black-box middleware components. In detail, we show how our approach provides an evolutionary and non-intrusive solution to the scalability limitations of DPWS and experimentally evaluate it with an implementation based on the the Web Services for Devices (WS4D) Java Multi Edition DPWS Stack (JMEDS).Comment: 28 pages, Technical Repor