Let's rokk! [Tudor Cret's blog]

January 25, 2010

Behind ciripescu.ro, a Windows Azure cloud application (part 1)

Filed under: Technologies — Tudor Cret @ 2:18 pm
Tags: , , , , , , ,

Intro

January 4th marks an important step towards enabling Microsoft’s customers and partners, to build and grow businesses on the Windows Azure platform. Microsoft announced that upgrade from Community Technology Preview (CTP) accounts of the Windows® Azure™ platform (i.e., Windows Azure, SQL Azure and/or Windows Azure platform AppFabric) to paid commercial subscriptions is available. At the moment just for a list of countries, list in which Romania is not included. At least until February 1, 2010 the CTP accounts can be used. After this date the storage accounts will become read-only.      

The good news is that finally we don’t have a CTP version anymore. The bad news is that it is no longer free. And it costs. How much? Just watch the pricing list here. And before knowing the total…take a pen and a paper or try TCO and ROI calculator. In our case for ciripescu.ro, one worker role and one web role we’ll start from a minimum of $50 per month.      

But what services we get? In three words: Availability, Durability, Scalability. That means:      

  • Data from the storage (I’m not speaking about database, I’m talking about storage…) will always be available. Data is replicated across 3 nodes, at least. No request to the storage should fail. Also the uptime for my workers and web roles is around 99.99%. And this because at least 3 machines serves a worker or web role.
  • Data from storage is never lost. As I said data is replicated over 3 nodes. At least one node Is available and durable to serve the requested data.
  • I can scale my application as easy as clicking on a button and using a pay-as-you-go service. Et voila, I can add a new role to my application. With a click I have a new machine working for me, which means no hardware, no administrative tasks, etc.

Of course, these are not all the benefits. More can be found here.      

The purpose of the current post is to make a summary of what is behind ciripescu.ro a simple micro-blogging application developed around the concept of twitter. This platform can be extended and customized for any domain.      

So our intention is to develop a simple one-way communication and content delivery network using Windows Azure. Let’s define some entities:      

  • User –  of course we can do nothing without usernames, passwords and  emails J Additional info can be whatever you want, just like an avatar, full name etc.
  • Cirip – defines an entry of maximum 255 characters, visible to everybody. Users content is delivered through this entity
  • Private Message – a private message between two users
  • Invitation – represents an invitation a user can send to invite more other users to use the application. 

I won’t enter in more details about what the application does, you can watch it in action (at least until the end of January L) at www.ciripescu.ro. For the next sections I will concentrate on how the application does all its functionalities. Configurations and deployment aren’t so interesting since they are exposed to any hello world azure application video or tutorial.      

High level view

First let’s take a look at the architecture:      

High level design of Ciripescu.ro

  

The webrole is what people traditionally view as a web application. VS project contains everything a normal ASP.NET web application would: aspx pages, user controls, web services, code behind (including business layer or data access layer), etc. In fact it can be converted to a normal web application with two clicks from the context menu. It may be even an ASP MVC application. All HTTP requests are served by Windows Azure to one of these Web Roles. I’m saying “one of them”, because scaling up such an application involves running for Web Roles, and possibly more Worker Roles. If one web role has “enough” requests to process then a new incoming request will be handled by one of the other web roles.  With just one click you can have more web roles and more worker roles. Just one click….and a bigger pay bill at the end of the month. Yes, but…if you have your own datacenter? More web roles and worker roles means…electricity, hardware and human force.  And hardware is part from the companie’s actives…      

The worker role can be best compare to a windows service. It’s an application that runs in the cloud and performs tasks that are not suitable for a web application. Anything that takes too long to process and would unreasonably delay the loading of a page should clearly execute asynchronously and out of the normal IIS pipeline. For instance ciripescu.ro sends all its emails using such a worker Role. Why? Well, as most of the other social networking sites, ciripescu.ro has the ability to import contacts from a yahoo messenger account for instance and then lets the user select which of them he wishes to invited. This means that with one click a user could make ciripescu.ro send out a few hundred emails. Such a task could take between a few minutes, up to an hour. Obviously the user can’t wait that long for the page to load. Another example: let’s say I have to send a SMS message from my web application and sending SMS through a SMS gateway takes more than 10 seconds. Et voila, I already have the worker; it should do the job, while the user is free to “walk” to the rest of the application. So we can have as web roles any web application(website, ASP.NET MVC application) and as worker roles  any class library project(C# or VB). I don’t see a reason for which we wouldn’t have multiple worker or web roles written in different languages. Now it would be interesting to see a mix of worker and web roles each one developed using different platforms, PHP, Java, .NET that works together in the same application in the cloud. What would mean all that? That Azure is flexibile and not dedicated only for .NET ? It’s not tested yet that a ASP.NET MVC web role can use a Java worker role, but it’s a challenge for the future time. Anyway Azure is a programatically flexibile. You can easily integrate the existing web applications with new ones. Also integration with “on-premises” applications can be easily done via Bus Services. More about Bus services and Windows Azure flexibility can be found on Windows Azure training kit or just watching videos from PDC  2009. 

More available in part 2, here.

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