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Friday, January 11, 2013

Checklist: is my app ready for the cloud?


The cloud is finally losing a bit of the hype and many organizations’ CIOs heard enough that are now ready to do something real with it. And that question comes to their mind: which application do I move first?

Enough has been said about the choice between IaaS, PaaS or SaaS that I assume the first step to the cloud will be towards raw infrastructure, giving up a bit of the sovereignty but still keeping all the power to architect and manage applications.

But the first moves to the cloud will lead many CIOs into a few mistakes. First off, they will think of the cloud as a simple shift of responsibility regarding the infrastructure management, thus making the cloud adoption become only a matter of SLA, data integrity and security.

As a consequence of the same assumption, they will think they could probably move their business critical applications over to the cloud “as is”, looking for a cloud provider that offers exactly the same manageability and features as the ones they were used to in their own data center.

> The cloud is a tremendous opportunity to start thinking differently


I’ve read two interesting articles recently that contain a couple of very important points about doing things with cloud infrastructures. The first one titled “Which Apps to Move to the Cloud?” starts by quoting Forrester research saying:
[...] you shouldn’t be thinking about what applications you can migrate to the cloud. That isn’t the path to lower costs and greater flexibility. Instead, you should be thinking about how your company can best leverage cloud platforms to enable new capabilities. Then create those new capabilities as enhancements to your existing applications… you have to think differently as you approach cloud development. There’s far more power in application design and configuration once you free yourself from assumed reliance on the infrastructure. The end result is new degrees of freedom for developers – if you embrace the new model.
Later, the author goes through the different types of applications being used in the enterprise comparing them to the layers of onions (yeah, just like Ogres). The inner layers are applications with most innovation, intellectual property and value to the company core busines, the outer layers are commodity apps. His conclusion is that maybe the outer layers are better to start with when moving to the cloud.

Again it’s only about risk. Let’s start with a lower risk (of loosing data or interrupting business processes) in exchange of the popular “more flexibility at lower cost” of the cloud.

The second article (very smart read, IMHO) appeared on cio.com tries to think of the cloud in the enterprise world, something that has very few success stories so far, listing some very important advices, one of them attracted my attention:
[...] a leading cloud provider would never consider adding any application to its portfolio without a clear plan for how it will scale over time. Corporate IT? Not so much. "They build infrastructure to scale out," Paquet says, "but if their applications don't, what problem have they actually solved?" Think scale first. And that may mean ruling out many packaged application. "Most of them are not built to scale out," says Paquet.
What we understand from these two articles is that the cloud gives you a new infrastructure footprint that “enables new capabilities” and thus it’s you who have to adapt yourself to the cloud and not vice versa. Moreover, you have “more power in application design and configuration” that application architecture does make a difference.

> Ok but... technically speaking, what exactly can I move out today?


Now that we got the above statements, we still want to start moving something to the cloud today and we don’t want to develop everything from scratch adding up delay to our cloud adoption. What both articles don’t explain clearly is: what are the technical characteristics of the applications that I can move to the cloud?

Here’s a checklist that helps you understanding if your application is cloud-ready:
  1. The application must be designed to scale by adding different instances of the same application process one next to another on different machines, applying some kind of mechanism to share the workload without depending on the OS.
    This methodology, that results into a both scalable and resilient app, is strictly required when moving to the cloud as you don’t know what kind of hardware is being used underneath (you can actually easily assume they’re just commodity servers)
  2. The application data store must be partitionable. If you have a high amount of data growing linearly, then you can split it into different chunks, each to be bound to one of the application nodes.
  3. The data store partitions should be able to be replicated on other nodes in order to achieve redundancy.
If you are running any application and that matches the above patterns, you can feel free to move it to the cloud today without worrying about loosing data or interrupting your business processes, provided that you make good use of the application configuration capabilities!

As I’m pretty sure you’ll have to go through some architectural review, while doing that, keep in mind to think only at the application level with nothing strictly depending on the operating system. This will give you extra freedom to migrate between cloud providers and complete self-sufficiency to implement your highly available application tiers in the way you prefer.

If you want to dig deeper into these principles, I advise you to read over Amazon Dynamo Paper that explains the theory and the trade-off between consistency and availability and that inspired great cloud-ready applications like Riak noSQL key-value store.


In conclusion, the cloud enables commodity IT infrastructures at extremely low price. With this in mind, you simply can’t demand that if you move your single instance database onto one virtual machine in the cloud, this will never go down. On the other hand, cloud infrastructures today offer all the mechanisms and features that, if mastered, can help you building the most highly available application clusters you ever had before.

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