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Containers and Microservices
Published in Haishi Bai, Zen of Cloud, 2019
Scaling out allows system capacity to be dynamically expanded by adding additional service instances. Scaling out stateless services is relatively easy—simply add more instances behind a load balancer and the workload will be distributed among all available instances. Scaling out stateful services, however, needs additional work. As you've seen in the previous section, to keep availability, the state of a stateful service is replicated to multiple secondaries. When you add more servers to handle an increasing workload, both the size of the state and the number of replicas increase, making replication an increasingly expensive task. Furthermore, because all writes still go through the primary regardless of number of secondaries, having more machines doesn't increase the system throughout.
Hypertext Transfer Protocol (HTTP)
Published in Akshi Kumar, Web Technology, 2018
HTTP is a stateless protocol. Cookies are an application-based solution to provide state retention over a stateless protocol. They are small pieces of information that are sent in response from the web server to the client. Cookies are the simplest technique used for storing client state. A cookie is also known as HTTP cookie, web cookie, or browser cookie. Cookies are not software; they cannot be programmed, cannot carry viruses, and cannot install malware on the host computer. However, they can be used by spyware to track a user’s browsing activities. Cookies are stored on a client’s computer. They have a lifespan and are destroyed by the client browser at the end of that lifespan.
Service-Oriented Computing
Published in Vivek Kale, Digital Transformation of Enterprise Architecture, 2019
Stateless: Services should be stateless because they scale more efficiently as any service request can be routed to any service instance. In contrast, stateful interactions do not scale efficiently because the server needs to track which service is serving which client and cannot reuse a service until the conversation is finished or a time-out has occurred.
Development of a CNC interpretation service with good performance and variable functionality
Published in International Journal of Computer Integrated Manufacturing, 2022
This paper mainly concentrates on an implementation of the interpretation module in cloud-CNC. A CNC interpretation service with variable interpretation ability and good performance is developed. Compared with current interpreter components, this interpretation service enables to cope with the diversity of NC programming language as the result of a composable mechanism. Besides, a conditional statement-based error-tolerant semantic analysis mechanism and an operation handle mechanism are proposed. This interpretation service is released as a RESTful service. REST, the abbreviation of REpresentational State Transfer, is a web standards-based architecture that users HTTP protocol and identifies stateless resources by URI or URL (Erl et al. 2017). RESTful services are more and more attractive thanks to the simplicity of REST. This interpretation service can be used independently for users to check and translate NC programs, like the stand-alone interpreter (SAI) developed by LinuxCNC. Either, it can interoperate with other CNC services seamlessly. The rest paragraphs are organized as follows: Section 2 first introduces NC programming languages and then retrospects current CNC interpreters, Section 3 illustrates the implementation mechanisms of this interpretation service while Section 4 presents its development. This interpretation service is tested in Section 5 and discussions and future work are presented in Section 6. Section 7 presents the conclusions of this paper.
Designing interoperable telehealth platforms: bridging IoT devices with cloud infrastructures
Published in Enterprise Information Systems, 2020
Kostas M. Tsiouris, Dimitrios Gatsios, Vassilios Tsakanikas, Athanasios A. Pardalis, Ioannis Kouris, Thelma Androutsou, Marilena Tarousi, Natasa Vujnovic Sedlar, Iason Somarakis, Fariba Mostajeran, Nenad Filipovic, Harm op den Akker, Dimitrios D. Koutsouris, Dimitrios I. Fotiadis
User authentication is handled from the R2D2 API using JSON web tokens (JWT) and typical email address and password credentials for identification. Each token is an encrypted object with certain expiration time that carries details about the user’s identity, which are passed in a header X-Auth-Token format. This action is stateless, as there are no sessions on the cloud server. If the token has expired, the query will return an appropriate error and the user will need to login again to get a new token. Single sign-ins for specific projects can also be supported. In these cases, the authentication is handled by a trusted third party and access is granted only to a specific portion of the R2D2 cloud services. When the third party makes a request, it includes a special JWT token with non-sensitive authentication details signed with a private key.
API deployment for big data management towards sustainable energy prosumption in smart cities-a layered architecture perspective
Published in International Journal of Sustainable Energy, 2020
Bokolo Anthony Jnr, Sobah Abbas Petersen, Dirk Ahlers, John Krogstie
The most widely architectural protocol for web-based applications is Representational State Transfer (REST) which was proposed by Roy Fielding (Fielding and Taylor 2000) for deploying large scale distributed systems based on client server, which suggests that deployment on each side can be accomplished separately. REST protocol employs a stateless procedure which suggest that each call comprises of information essential for execution and thus does not require status information from prior calls to be implemented (Karnouskos, Da Silva, and Ilic 2012). Over the years, REST APIs have become a vital component that allowed the dynamic pull of data from different databases in response to end-users’ requests or inputs, instead of pushing same static information to every user. REST is also suitable based on its tolerance and flexibility for third-party designers to develop web-based applications (Raetzsch et al. 2019). APIs utilise sets of methods that supports client-based applications to interact and transmit data such as energy data using JavaScript, REST, Simple Object Access Protocol (SOAP), and other web approaches for transmitting structured information (Chaturvedi and Kolbe 2018; McGrath et al. 2019). REST services are among the most widely deployed web services in use today, due partly to its simplicity and robust architecture that uses less bandwidth for connecting services. Although, few enterprises utilised other web service protocols such as Simple Object Access Protocol (SOAP) (McGrath et al. 2019).