The PK blog

Paspartu is French for “one size fits all”. Recently I’ve been coming across posts explaining and “promoting” the idea of spawning threads inside a worker role each one of them with a unique work to be done. All are sharing the same idea and all of them are describing the same thing.

The idea

You have some work to do, but you want to do it with the most efficient way, without having underutilized resources, which is one of the benefits of cloud computing anyway.

The implementation

You have a worker process (Worker Role on Windows Azure) which processes some data. Certainly that’s a good implementation but it’s not a best practice. Most of the time, your instance will be underutilized, unless your doing some CPU and memory intensive work and you have a continuous flow of data to be processed.

In another implementation, we created a Master-Slave pattern. A master distributes work to other slave worker roles, roles are picking up their work, do their stuff, return result and start over again. Still, in some cases that’s not the best idea either. Same cons as before. Underutilized resources, high risk of failure. If the master dies, unless properly designed, your system dies. You can’t process any data.

So, another one appeared. Inside a worker role, spawn multiple threads, running their own processes or methods, doing their work and return result. Underutilization is minimized, Thread Pool is doing all the hard work for us and as soon as .NET 4.0 is supported on Windows Azure, parallelization is easy and, allow me to say, mandatory. But what happens if the worker instance dies? Or restarts? Yes, your guess is correct. You lose all threads and all the processing done by that moment, is lost, unless you persist it somehow. If you had multiple instances of your worker role to imitate that behavior, that wouldn’t happen. You’ll only lose data from the instance that died.

As Eugenio Pace says “You have to be prepared to fail” and he’s right. Every single moment, your instance can die, without a single notice and you have to be prepared to deal with it.

Oh, boy.

So really, there is no single solution or best practice. For me, it’s best guidance. Depending on your scenario, one of the solutions above or even a new one, can fit better for you than for others. Every project is unique and has to be treated as such. Try to think out of the box and remember that this is deep water for everyone. It is just some of us swim better..

PK.

Every single time something new emerges in the IT market, there are three distinct categories of people: Early adopters, Late majority, Skeptics. Each one of them has its own reasons and its own concerns about when, why and if they are going to adapt to this new technology, either completely or in a hybrid mode.

All of them have some things in common. They share the same concerns about security, billing, taxes, availability, latency and probably some others.

Concerns and my thoughts.

Billing is something that can easily be solved and explained by clever and good marketing. Unfortunately, there is no such thing as local billing. Cloud computing services are truly global and the same billing model, the same prices, the same billing methods have to be used to provide a fair and consistent service to every customer. This has to change. For some markets, a service can be really cheap, but for some others can be really expensive. Increasing the price in some countries and decreasing in some others can make the service more fair and more adoptable. Using a credit card to identify the country is a good method, but there is a problem. It’s called taxes.

Taxes is a way for a government to make money. In many countries, Greece being one of them, having a credit card with a decent limit it’s a privilege. Unfortunately I mean it in a bad way. Interest is quite high and with such an unstable tax policy you can never be sure if there won’t be any extra fees you might have to pay sooner or later. But I guess this is not only our problem but for some other countries too, mostly emerging markets. Providing another way of paying monthly fees for service usage, can easily overcome this.

Security. Oh yes, security. Countless questions during presentations and chats are about security. Tons of “what if”. Yes, it’s a big issue. But too much skepticism is never good. I believe people are not worried about security issues like data leakage/stolen/etc. There are worried because they somehow lose control of their information. At least this is what they believe. The idea that their data are not stored in their own hardware but somewhere else and not even in the same country, terrifies them. I’m not sure if there is anything that can be done to subdue this concern but at least, there can be some localized data centers for example, banks were regulatory laws demand data to be stored in the same country, if not on-premises owned by the bank. Private cloud could probably meet those regulations.

Latency. That’s an easy one. Its principal is the same as security. My data are over there and there might be a significant latency until I get a response. Yes there is a delay no it’s not that big, probably somewhere between 60 to 100 ms. For applications that are not real time, this is really really low. You can even play shoot’em’up games with 100ms latency. The only thing we can do, is have a requirement for a decent DSL line from our customers in case our application, locally installed, is accessing a cloud service. Also picking the right region to deploy our application can have a significant impact on latency.

Availability. People are worried about their data not being available when most needed. The further their data are, the more points of failure. Their internet line, their ISP line, a ship cutting some cables 4000km away. Most, if not all, cloud service providers provide 3 or 4 “nines” of uptime and availability, but there are a lot of examples of services failing from unpredicted code or human errors (eg Google). Other companies have proved more trustworthy and more reliable.

Conclusion

Concluding this post, I want to make something clear. I’m not part of those distinct groups of people. I started playing with cloud computing services right after Amazon removed beta label from its AWS service, back in 2008 (April if I recall correct), with Windows Azure following at PDC ‘08. I had my first token back then and started playing with it. I’ve seen Windows Azure shape and change within those two years in something amazing and really ground breaking. Windows Azure can successfully lower or even eliminate your concerns in some of the matters discussed above, but there is room from improvement and always will be. I’m going to dig a little deeper on those matters and try to provide more concrete answers and thoughts.

Thank you for reading so far,

PK.

Yes, it is.

Table storage has multiple replicas and guarantees uptime and availability, but for business continuity reasons you have to be protected from possible failures on your application. Business logic errors can harm the integrity of your data and all Windows Azure Storage replicas will be harmed too. You have to be protected from those scenarios and having a backup plan is necessary.

There is a really nice project available on Codeplex for this purpose: http://tablestoragebackup.codeplex.com/

PK.