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Easy Background Processing with WebAPI and Windows Azure

The Problem

Assume, for example, that you are developing your own mobile app (or apps, in my case) and want to be able to send push notifications to these apps every once in a while.

You would require a server that will run somewhere in the background, collect new information every given interval and send relevant notifications to the client apps. You would also need to allow the mobile apps to register and unregister from that server, and supply a simple management console user interface for operations such as browsing though your logs, changing intervals and behaviors and so on.

Thinking it through you realize that you also require a SQL database, that the server has to be fully secured (you would not like anyone hacking in and pushing messages in your behalf into your mobile app, used by unknown users..), and that it has to be reliable and always ready.

Now, you could start by trying to locate a suitable and available server(s) and get it allocated for your purposes, or go out and purchase one. You would also have to make sure that the server (or servers) is licensed and installed with all that is required, from operating system through database engines, all the way to the web-server and other packages with the latest version. Your server should also be exposed to the internet but yet secured.

But even when you finally have that server running, who is going to make sure that the server is always up, operational and taken care of? What about variable bandwidth and storage capacities?

A simple and great solution for your background processing – Windows Azure.

The Solution

For my server, I start off by creating a Windows Azure SQL Database (No need to put up a fully secured, reliable, always ready SQL Server – CHECK!).

Back in my Visual Studio 2012, I use the “Server Explorer” tab to further create the tables, relations, keys etc., as Windows Azure SQL Databases act as any standard remote SQL server databases, just in the cloud. (No special tools – CHECK!)

Two pieces were still missing from the puzzle: the background service and a management console. Simple solution there – I create a Windows Azure Cloud Service composed of a Worker role and Web role. The Worker role would be used for background processing and the Web role would serve as the management console and Web-API host.

NOTE     A Windows Azure Web Site would not be a good enough solution for these purposes as it becomes dormant after a short timeout of not receiving new calls, thus any background service will stop working.

You have two options: create both elements through the Windows Azure console and download a ready-made Visual Studio project, or create what you need in Visual Studio using wizards and have Visual Studio take care of creating whatever is required on Azure for you.

I usually choose the latter as it is easier for me to do it all from the Visual Studio environment, where I have everything I need. You would need to install the Windows Azure SDK in order to have the cloud options in your Visual Studio.

Creating a cloud service is as simple as “File/New/Cloud/Windows Azure Cloud Service” (assuming you already have the required live account):

Adding a Windows Azure Cloud Service project

and selecting the desired roles:

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The wizard creates ready-made solution and projects for the selected roles, already set to work with Entity Framework 5. The Worker role project already contains stubs for the “Run” and “OnStart” method overrides, allowing you to inject your business logic into the background service, while the Web role (if the preferred MVC 4 pattern selected) is already a full-blown website, with REST support, controllers, models, and everything that you need to form a secured websites, including pre-defined ASP.NET membership.

At this stage, both projects can already be published to Windows Azure.  You only have to worry about your specific code. You can also debug both projects using the Visual Studio and the “Windows Azure Compute Emulator” and “IIS Express”, that are installed as part of the Windows Azure SDK install.

So, what do we have here?

We just setup a WebAPI server, a website and a background service running against a SQL server in record time and with minimal effort. Having all of them running on Windows Azure, we also ensured reliability, manageability and consistency for our services.

Using the above steps, it took me less than a day to complete the rest of the code logic and get a push notifications server up and running. Want to see it in action? Check out the Toronto Events and Festivals Windows 8 and Windows Phone 8 apps as well as the Trashswag Windows 8 and Windows Phone 8 apps. Both use this background processing cloud service architecture to collect new information and send notifications to the apps.

If you’d like to go deeper into this concept, I’ve put some demo code on my SkyDrive. Going through the examples, you’ll see that there was very little code required in order to get Windows 8/Windows Phone 8 apps connected to the WebAPI based Windows Azure app. Please note that the WebAPI MVC 4 project uses a bunch of NuGet packages, automatically installed by the wizard within my project. Write me or comment below if you have any questions or need some help.

Featured on MSDN Canada’s Canadian Developer Connection

Tile? Secondary tiles? Live tile?

Thanks to everyone who attended my session about “Engaging users with live tiles and notifications” to the @DevTeachConfere.

The slides and demo code are available for download here.

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Azure Mobile Services vs. REST vs. XML Web-Services

You’re planning a new system, and already decided that you want the data to be hosted on the cloud.

Now, should you use web-services? REST (using WEB-API for example)? maybe Windows Azure Mobile Services?

Let’s see the differences between these technologies, but first- a short overview:

XML Web-services

The old and well-established type of remote operation mechanism, allowing you to expose your server application’s abilities and services using SOAP-XML contracts that can later be consumed by every client app capable of encoding and decoding XML messages.

This mechanism is platform-independent, and if you stick to basic SOAP-XML structures you can have clients running Microsoft operating-systems, Apple’s, Android or anything else working against your server application, having SOAP-XML as the lowest-common-denominator and the language spoken between your server application and the clients.

XML Web-Services may (and usually will) also supply metadata (WSDL/UDDI) that allows clients to work with your application server without any previous knowledge or information about the server application’s API structure or technology, and may also adapt to API format changes quite easily.

This type of services are cross-platform, self-explanatory, mobilizes well structured data and supports additional communication layers such as WS-Security or WS-Addressing.

REST:

“REST” (stands for “representational state transfer”) uses a much simpler approach than XML Web-Services.

While XML Web-Services rely on HTTP or other types of transport layers to send and receive XML messages to and from the server, REST goes back to the source and uses the HTTP command verbs themselves to perform operations and transfer information to and from your application server.

This protocol is much looser than XML Web-Services and will attempt to deduce what operation to perform and how to use the transferred parameters from the HTTP VERB and URI used.

The actual data can be transferred in any format, such as XML or JSON and is not bound to comply with any type of pre-defined protocol.

REST is light-weight, portable and easy to consume by HTTP enabled clients. You can have your service up and running in practically no-time.

On the other hand, though these services may also be self-explanatory (using “WADL”), REST might be less suitable if you require a more strict service API approach, defining exactly what operations to perform and the data to be transferred.

Also, additional communication layers are not supported, beyond HTTP and HTTPS.

Both XML Web-Services and REST services can be hosted on Windows Azure quite easily, and can both be accessed by mobile clients.

Azure Mobile Services:

Windows Azure Mobile Services is a set of Windows Azure services exposed as a pre-defined set of WEB-API hosted REST services designed to be consumed by mobile clients.

When creating mobile services, you can use the Windows Azure wizards to also create Windows 8, Windows Phone 8, Android or iOS client apps, already set-up to connect to your service using dedicated libraries for each platform.

The server is created for you, pre-defined to manage data on the cloud, manage users and authentication, schedule maintenance scripts and custom logic and integrate push notifications.

Azure Mobile Services biggest advantage is that it takes most of the common aspects of the design, coding and testing of the application server and mobile clients off your hands and allows you to focus on the custom features only.

“So, what should I use?”

Well, if you’re application server is intended to serve older/existing XML web-service clients, XML web-services are your only hope, though you might want to consider adding a REST interface to your application server as well.

But, if you are planning an application server that is intended to serve mobile clients, there’s no reason for you to re-invent the wheel when Windows Azure Mobile Services can have you kick-started very quickly with many aspects of the application server.

Moreover, whenever you are required to create the complete solution you can use the Windows Azure wizards to have your client apps already created (for all supported platforms) and set-up to use your application server.

As these services are exposed using REST, you can also have your application server accessible for other types of clients, just like any other REST application server, consulting the Windows Azure Mobile Services REST API Reference.