1.7 PLATFORM AS A SERVICE PROVIDERS

Public Platform as a Service providers commonly offer a development and deployment environment that allow users to create and run their applications with little or no concern to low-level details of the platform. In addition, specific programming languages and frameworks are made available in the platform, as well as other services such as persistent data storage and inmemory caches.

1.7.1 Features

Programming Models, Languages, and Frameworks.

Programming models made available by IaaS providers define how users can express their applications using higher levels of abstraction and efficiently run them on the cloud platform. Each model aims at efficiently solving a particular problem.

For user convenience, PaaS providers usually support multiple programming languages. Most commonly used languages in platforms include Python and Java (e.g., Google AppEngine), .NET languages (e.g., Microsoft Azure), and Ruby (e.g., Heroku). Force.com has devised its own programming language (Apex) and an Excel-like query language, which provide higher levels of abstraction to key platform functionalities.

A variety of software frameworks are usually made available to PaaS developers, depending on application focus. Providers that focus on Web and enterprise application hosting offer popular frameworks such as Ruby on Rails, Spring, Java EE, and .NET.

Persistence Options.

A persistence layer is essential to allow applications to record their state and recover it in case of crashes, as well as to store user data. Traditionally, Web and enterprise application developers have chosen relational databases as the preferred persistence method.

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Case Studies

Aneka.
App Engine
Microsoft Azure
Force.com

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2.1 VIRTUAL MACHINES PROVISIONING AND MANAGEABILITY

In this section, we will have an overview on the typical life cycle of VM and its major possible states of operation, which make the management and automation of VMs in virtual and cloud environments easier than in traditional computing environments As shown in Figure above, the cycle starts by a request delivered to the IT department, stating the requirement for creating a new server for a particular service. IT administration to start seeing the servers’ resource pool, matching these resources with the requirements, and starting the provision of the needed virtual machine. Once provisioned machine started, it is ready to provide the required service according to an SLA, or a time period after which the virtual is being released.

1.2 ROOTS OF CLOUD COMPUTING

We can track the roots of clouds computing by observing the advancement of several technologies, especially in hardware (virtualization, multi-core chips), Internet technologies (Web services, service-oriented architectures, Web 2.0), distributed computing (clusters, grids), and systems management (autonomic computing, data center automation). Below Figure shows the convergence of technology fields that significantly advanced and contributed to the advent of cloud computing. . We present a closer look at the technologies that form the base of cloud computing, with the aim of providing a clearer picture of the cloud ecosystem as a whole. 1.2.1 From Mainframes to Clouds 1.2.2 SOA, Web Services, Web 2.0, and Mashups 1.2.3 Grid Computing 1.2.4 Utility Computing 1.2.5 Hardware Virtualization 1.2.6 Virtual Appliances and the Open Virtualization Format 1.2.7 Autonomic Computing ______ Cloud computing has its roots in several technologies and developments, including virtualization, gr...

2.1.1 VM Provisioning Process

Steps to Provision VM. Here, we describe the common and normal steps of provisioning a virtual server: Firstly, you need to select a server from a pool of available servers (physical servers with enough capacity) along with the appropriate OS template you need to provision the virtual machine. Secondly, you need to load the appropriate software (operating system you selected in the previous step, device drivers, middleware, and theneeded applications for the service required). Thirdly, you need to customize and configure the machine (e.g., IP address, Gateway) to configure an associated network and storage resources. Finally, the virtual server is ready to start with its newly loaded software. These are the tasks required or being performed by an IT or a data center’s specialist to provision a particular virtual machine.

Cloud Computing

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