Saturday 13 March 2010

Cloud computing enables and forces us to do proper engineering

Very often testing is a second class citizen in the IT world. It’s not like software is not tested at all but it’s far from being perfect:

  • the testing environment is nothing like production environment
  • performance testing is nonexistent

This leads to problems that you can observe only in production. The process of fixing those kind of issues tends to take a lot of time because most often developers have very limited access to production and the set of tools they can use for debugging is limited. A permanent testing environment that matches production is very expensive and that’s why businesses take risk and deploy applications to production without proper testing. Very often they are unlucky and the price they pay is much higher than the price of proper testing. It’s like a mortgage, you get a lot of money quickly but then later on you have to pay the interest. Nothing is for free. With Cloud computing this is no more such a big problem. If your production deployment requires 50 servers then you can provision a testing environment which looks exactly like production within minutes. What is more once your are done with testing you can simply get rid of the whole environment. But this sounds like a lot of effort. Doesn’t it? Well, that’s true only if the whole process in manual. If it’s automated it’s not a problem at all. You can write your own scripts or use services like Right Scale that will help you with this. The point is that the use of Cloud computing forces you to automate your software development processes which is good. The same applies to performance testing. You can setup a testing lab only for the duration of a test. You can read here how MySpace leveraged Cloud computing to make sure it can handle 1 million of concurrent users.

I’m sure everybody heard at least once that scaling applications in the Cloud is easy. As you can expect this is not entirely true. It might be true in the marketing world though :). If you simply move your application from your own data centre to a Cloud there is a good chance that it will be much slower and less reliable. Why? Most Cloud providers offer you a few predefined server configurations that you can choose from. What is more most of them are virtual servers. This means that you don’t have any control over the hardware the application will run on. If the Cloud provider can’t match your existing setup then there is a good chance the application will be slower. Even if you manage to get enough CPUs and RAM you might still suffer from slow disk IO and the fact that the machines are less reliable than you would expect. You can read more about that here. The bottom line is that that you can’t expect the application to simply run unchanged in the Cloud.  One of the ways of aligning the application with the Cloud is making sure that it can run on multiple servers at the same time. This basically prevents you from building monolithic systems.

Security is another topic that tend to get very little attention. The reason is that there is an implicit assumption that the application will always run locally thus nobody from outside will have access to it. Obviously this is a fallacy and a huge security hole. Nobody can see it (or everybody can hide it) because it’s implicit. Without addressing this problem you can’t really move your application to the Cloud which forces you to take care of it. Cloud computing makes a lot of things very explicit which is a very good thing. There are way too many secret handshakes and implicit assumptions that we take advantage of to build applications nowadays. Cloud Applications Architectures deals with security in the Cloud quite extensively. It’s a good book that is a bit outdated and a bit too much focused on the Amazon Cloud but still worth reading.

Disaster recovery is very similar to load testing. Everybody knows that it’s needed and everybody has a plan how to do it but the plan never gets executed because it takes way too much time and resources. Again, Cloud computing makes it cheaper and easier to do. What is more you get more options. You can start with a plan that deals with failures of a single server and extend it, if it’s required, to procedures that can deal with data centres or even whole countries being offline.

As you can see you can gain a lot from Cloud computing but it doesn’t come for free and more than likely you will have to redesign your applications and rethink your processes to make sure you can take full advantage of what Cloud computing has to offer.

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