tirsdag den 17. marts 2009

Developing cloud apps: What's different

Om 5 år er 50% af alle web apps Cloud baserede ... måske flere og måske før ...

In 5 years time 50% of all web apps are Cloud based ... maybe more and maybe sooner ...


By Paul Krill

Statelessness, server failure, new databases, and fast-changing platforms will challenge developers

Statelessness and server failures are givens in the cloud
"The big change now is that software itself is able to provision the resources that the application needs," says Lew Tucker, Sun's CTO of cloud computing. Using APIs, developers writing applications for the cloud can design them so that they request more resources from the cloud provider.

Developers need to design for redundancy and acknowledge that commodity machines are being leveraged in the cloud, says Amitabh Srivistava, Microsoft's corporate vice president for the Windows Azure cloud platform. "It's a guarantee the machines are going to fail, so you have to design your application that you're running in the cloud for redundancy," he says.

Building for the cloud requires designing stateless applications, Srivistava says. "If you have state, then that becomes a problem. The model in the cloud is if something dies, you kill it and reincarnate it" by designing stateless applications, he notes. With the cloud, "there's no concept of a local disk. There's no registry, for example. But that's all encapsulated by being a stateless app." [...]

Databases aren't the same in the cloud
The uses of abstraction and statelessness also have database implications. For example, Azure presents developers with a different perspective on databases than the standard relational model, said Ben Day, president of Benjamin Day Consulting. The Azure storage engine does not use a standard relational database, so "a lot of the stuff you would do if you were developing a standard app using a standard relational database just doesn't make a lot of sense anymore," Days says. He cites as an example the relational database concept of stored procedures, in which query logic is close to the actual data itself. This is no longer applicable in the Azure cloud.. [...]

Get used to rapid change in the cloud
Model Metrics, a consulting company, has implemented applications on Salesforce.com and other clouds. It has found that a major difference between cloud-based application development and Web and client-server development is that "things change much more rapidly in the cloud," says CTO John Barnes. [...]

You can let go of most plumbing concerns in the cloud
But the use of loosely coupled Web services offered on the cloud makes it an easier development platform, Barnes says. Developers can focus on innovation and business logic instead of worrying about plumbing and infrastructure such as the operating system and hardware, said Barnes. The Salesforce.com Force.com cloud, for example, offers security, workflow, administration, and load-balancing. [...]

Read more: http://www.infoworld.com/archives/emailPrint.jsp?R=printThis&A=/article/09/03/11/10NF-cloud-app-dev_1.html

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