Deploy web site to azure and traditional IIS

Question

I currently work with a legacy asp.net web application and one of the requirements going forward is that it be deployable to windows azure.

I would like to know how difficult it will be to manage deployment to both Azure and a traditional IIS web server.

Azure seems to require a specific customized version of a web applicaiton project is it possible to deploy the customized web application to a standard IIS instance once it has been converted.

EDIT:

It is a ASP.NET Web Application rather than a Web Site (compiles everything into one dll)

UPDATE:

In the end due to the amount of work involved in converting the application to work in Azure and the cost of Azure compared with other cloud solutions it was decided to go with a traditional Cloud hosted virtual server.

And thank you for the really good answers.

Answer 1

Whether or not you can deploy your application to Azure almost as is depends a lot on how your application works. Azure pretty much requires your application be stateless. If it's a plain vanilla web application that stores data in the session or application cache only and saves data to a database only, then you can deploy it to Azure.

If you have stateful services running like background threads (which is bad anyways), or if you save data to the file system (besides temporary caching), then you may have issues. Really, the issues moving to Azure are really the same as moving to any multi-server load balanced solution. One caveat is permanent storage.

If you need to store data in a place other than the database, then you're best off working with Azure's storage solution which has an API and client library for storing binary data, key/value data (they call it tables, but really, it's not tables), and queues. They also do have a transparent blob-as-file-system option for compatibility. If you want to use these in your app that also is used outside of Azure then you need to write an extra layer between your code and the Azure client library that supports both Azure services and standard local service. Azure SDK does include emulators for Azure services, but they're definitely not meant for production use.

As far as the mechanics of Azure-specific projects, that is actually not that difficult. Yes, you need to create an Azure-specific project in your solution that defines the Web Role and what gets deployed, but it will reference your existing Web Application, not the other way around. You can deploy the Azure Web Role to Azure or you can continue to deploy the existing application to IIS normally and concurrently.

Web Site, Web Application, MVC, really doesn't make much of a difference. Actually doesn't have to be .NET either. Can be PHP or Java or whatever you want to put on your VM. It'll all work the same as far as Azure is concerned.

MS likes to push Azure as a Platform-as-a-Service (Paas) solution where they have a ton of services they offer and you run apps on their standard platform, and contrasts that with Amazon AWS which they call Infrastructure-as-a-Service (Iaas) which is "just" a Virtual Machine. However, MS is really just as much a IaaS solution as AWS, perhaps even more so. The only difference between AWS and Azure is AWS allows you to choose what to install on your VM and with Azure you have to use Windows Server 2008 R2 as the basis for your VM (but you can customize the VM image to install custom software on top of windows). With both Azure and AWS, the hosts offer additional PaaS services you can take advantage of for data storage and message routing. AWS also offers tons of extra services like video streaming.

Also note that with Azure (and AWS I think) you can use the services they offer even in a non-hosted application. If you want to use Azure's data storage from a non-Azure application, you can do that, it's just HTTP REST calls to get/put data. The only differences you pay for data in/out between datacenter and your non-datacenter-hosted application which would be free if the app was also inside the datacenter (just the data in/out is free in-datacenter, you still have storage and transaction fees).

Answer 2

A few things:

• Samuel Neff's answer mentioned mounting a file system in a blob (a Cloud Drive). Only one instance may lock this cloud drive for writing, so it does not behave like a network file share. You'll need to plan for this.
• You'll need to integrate with the Windows Azure diagnostics subsystem, to gain visibility into your app's run state (e.g. performance counters, trace logs, etc.).
• If there are 3rd-party apps that your web app depends on, you'll need to install these. These actually get installed as part of the role instance's boot process, either via your OnStart() event handler or as a startup task. The latter allows for admin-level installs (including registry changes, COM component installations, etc.). You'll need to carefully manage these installations, as they impact the boot time of the instance.
• For an asp.net app, you'll need to think about session state. In-proc session state won't work, because each instance will have its own state store in memory. The SQL Azure session state provider doesn't have background cleanup agents, so you'll need to build this into your web or worker role instance (see this blog post by the SQL Azure team for the implementation). The best option is to use the AppFabric Cache, a new service that just went into production. This cache-as-a-service provides an custom session state provider for asp.net as well. Note: As of today, the AppFabric Cache service is only accessible via a .NET interface; there's no REST interface for it (all other storage services - tables, blobs, queues - have a REST interface). .NET, Java, and PHP all have storage client libraries. Ruby has one from the open source community.
• You'll have to manage scaling out to more than one instance, when the need arises. This is not a built-in service today, but there are 3rd-party services such as ParaLeap's AzureWatch. There's also Microsoft's System Center Operations Manager, which now has Windows Azure monitoring support. You'll also need to handle scale-back situations, where you reduce the number of server instances.

I have some additional details in an answer for a similar StackOverflow question, here.