One of the most common questions in developing ASP.NET applications on Windows Azure is how to manage session state. The intention of this article is to discuss several options to manage session state for ASP.NET applications in Windows Azure.

What is session state?

Session state is usually used to store and retrieve values for a user across ASP.NET pages in a web application. There are four available modes to store session values in ASP.NET:

1. In-Proc, which stores session state in the individual web server’s memory. This is the default option if a particular mode is not explicitly specified.
2. State Server, which stores session state in another process, called ASP.NET state service.
3. SQL Server, which stores session state in a SQL Server database
4. Custom, which lets you choose a custom storage provider.

You can get more information about ASP.NET session state here.

In-Proc session mode does not work in Windows Azure

The In-Proc option, which uses an individual web server’s memory, does not work well in Windows Azure. This may be applicable for those of you who host your application in a multi-instance web-farm environment; Windows Azure load balancer uses round-robin allocation across multi-instances.

For example: you have three instances (A, B, and C) of a Web Role. The first time a page is requested, the load balancer will allocate instance A to handle your request. However, there’s no guarantee that instance A will always handle subsequent requests. Similarly,the value that you set in instance A’s memory can’t be accessed by other instances.

The following picture illustrates how session state works in multi-instances behind the load balancer.

Figure 1 – WAPTK BuildingASP.NETApps.pptx Slide 10

The other options

1.     Table Storage

Table Storage Provider is a subset of the Windows Azure ASP.NET Providers written by the Windows Azure team. The Table Storage Session Provider is,in fact, a custom provider that is compiled into a class library (.dll file), enabling developers to store session state inside Windows Azure Table Storage.

The way it actually works is to store each session as a record in Table Storage. Each record will have an expired column that describe the expired time of each session if there’s no interaction from the user.

The advantage of Table Storage Session Provider is its relatively low cost: $0.14 per GB per month for storage capacity and $0.01 per 10,000 storage transactions. Nonetheless, according to my own experience, one of the notable disadvantages of Table Storage Session Provider is that it may not perform as fast as the other options discussed below.

The following code snippet should be applied in web.config when using Table Storage Session Provider.

<sessionState mode="Custom" customProvider="TableStorageSessionStateProvider">   <providers>     <clear/>    <add name="TableStorageSessionStateProvider"         type="Microsoft.Samples.ServiceHosting.AspProviders.TableStorageSessionStateProvider" />   </providers>
</sessionState>

You can get more detail on using Table Storage Session Provider step-by-step here.

2.     SQL Azure

As SQL Azure is essentially a subset of SQL Server, SQL Azure can also be used as storage for session state. With just a few modifications, SQL Azure Session Provider can be derived from SQL Server Session Provider.

You will need to apply the following code snippet in web.config when using SQL Azure Session Provider:

<sessionState mode="SQLServer"
sqlConnectionString="Server=tcp:[serverName].database.windows.net;Database=myDataBase;User ID=[LoginForDb]@[serverName];Password=[password];Trusted_Connection=False;Encrypt=True;"
cookieless="false" timeout="20" allowCustomSqlDatabase="true"
/>

For the detail on how to use SQL Azure Session Provider, you can either:

• Follow the walkthrough from this post.
• Or use ASP.NET Universal Providers via Nuget.

The advantage of using SQL Azure as session provider is that it’s cost effective, especially when you have an existing SQL Azure database. Although it performs better than Table Storage Session Provider in most cases, it requires you to clean the expired session manually by calling the DeleteExpiredSessions stored procedure. Another drawback of using SQL Azure as session provider is that Microsoft does not provide any official support for this.

3.     Windows Azure Caching

Windows Azure Caching is probably the most preferable option available today. It provides a high-performance, in-memory, distributed caching service. The Windows Azure session state provider is an out-of-process storage mechanism for ASP.NET applications. As we all know, accessing RAM is very much faster than accessing disk, so Windows Azure Caching obviously provides the highest performance access of all the available options.

Windows Azure Caching also comes with a .NET API that enables developers to easily interact with the Caching Service. You should apply the following code snippet in web.config when using Cache Session Provider:

<sessionState mode="Custom" customProvider="AzureCacheSessionStoreProvider">   <providers>     <add name="AzureCacheSessionStoreProvider"           type="Microsoft.Web.DistributedCache.DistributedCacheSessionStateStoreProvider, Microsoft.Web.DistributedCache"           cacheName="default" useBlobMode="true" dataCacheClientName="default" />   </providers>
</sessionState>

A step-by-step tutorial for using Caching Service as session provider can be found here.

Other than providing high performance access, another advantage about Windows Azure Caching is that it’s officially supported by Microsoft. Despite its advantages, the charge of Windows Azure Caching is relatively high, starting from $45 per month for 128 MB, all the way up to $325 per month for 4 GB.

Conclusion

I haven’t discussed all the available options for managing session state in Windows Azure, but the three I have discussed are the most popular options out there, and the ones that most people are considering using.

Windows Azure Caching remains the recommended option, despite its cons but developers and architects shouldn’t be afraid to decide on a different option, if it’s more suitable for them in a given scenario.

This post was also published at A Cloud Place blog.

This is the second article of a two-part introduction to Windows Azure. In Part 1, I discussed the Windows Azure data centers and examined the core services that Windows Azure offers. In this article, I will explore additional services available as part of Windows Azure which enable customers to build richer, more powerful applications.

Additional Services

1. Building Block Services

‘Building block services’ were previously branded ‘Windows Azure AppFabric’. The main objective of building block services is to enable developers to build connected applications. The three services under this category are:

(i) Caching Service

Generally, accessing RAM is much faster than accessing disk, including storage and databases. For that reason, Microsoft have developed an in-memory and distributed caching service to deliver low latency, high-performance access, namely Windows Server AppFabric Caching. However, there are some activities, such as installing and managing, and some hardware requirements like investing in clustered servers, which have to be handled by the end-user.

Windows Azure Caching Service is a self-managed, yet distributed, in-memory caching service built on top of the Windows Server AppFabric Caching Service. Developers will no longer have to install and manage the Caching Service / Clusters. All they need to do is to create a namespace, specify the region, and define the Cache Size. Everything will get provisioned automatically in just a few minutes.

Creating new Windows Azure Caching Service

Additionally, Azure Caching Service comes along with a .NET client library and session providers for ASP.NET, which allow the developer to quickly use them in the application.

(ii) Access Control Service

Third Party Authentication

With the trend for federated identity / authentication becoming increasingly popular, many applications have relied on authentication from third party identity providers (IdPs) such as Live ID, Yahoo ID, Google ID, and Facebook.

One of the challenges developers face when dealing with different IdPs is that they use different standard protocols (OAuth, WS-Trust, WS-Federation) and web tokens (SAML 1.1, SAML 2.0, SWT).

Multiple ID Authentication

Access Control Service (ACS) allows application users to authenticate using multiple IdPs. Instead of dealing with different IdPs individually, developers just need to deal with ACS and let it take care of the rest.

AppFabric Azzess Control Services

(iii) Service Bus

Windows Azure’s Service Bus allows secure messaging and connectivity across multiple network hierarchies. It enables hybrid model scenarios, such as connecting cloud applications with on-premise systems. The Service Bus allows applications running on Windows Azure to call back to on-premise applications located behind firewalls and NATs.

Service Bus Diagram

Migrating from an on-premise Windows Communication Foundation (WCF) framework to the Service Bus is trivial as they use a similar programming approach.

2. Data Services

Data Services consists of SQL Azure Reporting and SQL Azure Data Sync, both of which are still currently available as Community Technology Previews (CTP).

(i)  SQL Azure Reporting

SQL Azure Reporting aims to provide developers with a service similar to that of the current SQL Server Reporting Service (SSRS), with the advantages of being in the cloud. Developers are still able to use familiar tools such as SQL Server Business Intelligence Development Studio. Migrating on-premise reports is also easy as SQL Azure Reporting is essentially built on top of SSRS architecture.

(ii) SQL Azure Data Sync

SQL Azure Data Sync is a cloud-based data synchronization service built on top of theMicrosoft Sync Framework. It enables synchronization between a cloud database and another cloud database, or with an on-premise database.

SQL Azure Data Sync

(from Windows Azure Bootcamp)

3. Networking

Three networking services are available today:

(i) Windows Azure CDN

The Content Delivery Network (CDN) caches static content such as video, images, JavaScript, and CSS at the closest node to users. By doing so, it improves performance and provides the best user experience. There are currently 24 nodes available globally.

Windows Azure CDN Locations

(ii) Windows Azure Traffic Manager

Traffic Manager is designed to enable high performance and high availability of web applications, by providing load-balancing across multiple hosted services in the six available data centers. In its current CTP guise, developers can select one of the following rules:

• Performance – detects the location of the user traffic and routes it to the best online hosted service based on network performance.
• Failover – based on an ordered list of hosted services, traffic is routed to the online service highest on the list.
• Round Robin – equally distributes traffic to all hosted services.

(iii) Windows Azure Connect

Windows Azure Connect supports secure network connectivity between on-premise resources and the cloud by establishing a virtual network environment between them. With Windows Azure Connect, cloud applications appear to reside on the same network environment as on-premise applications.

Windows Azure Connect

(from the Windows Azure Platform Training Kit)

Windows Azure Connect enables scenarios such as:

• Using an on-premise SMTP Server from a cloud application.
• Migrating enterprise apps which require an on-premise SQL Server to Windows Azure.
• Domain-join a cloud application running in Azure to an Active Directory.

4. Windows Azure Marketplace

Windows Azure Marketplace is a centralized online market where developers are able to easily sell their applications or datasets.

(i) Marketplace for Data

Windows Azure Marketplace for Data is an information marketplace allowing ISVs to provide datasets (either free or paid) on any platform, and available to the global market. For example, Average House Prices, Borough provides annual and quarterly house prices based on Land Registry data in the UK. Developers can then subscribe and utilize this dataset to develop their application.

(ii) Marketplace for Applications

Windows Azure Market Place for Applications enables developers to publish and sell their applications. Many, if not all of these applications are SAAS applications built on Windows Azure. Applications submitted to the Marketplace must meet a set of criteria.

Conclusion

To conclude, we have examined the huge investment that Microsoft is making and will continue to make in Windows Azure, the core of its cloud strategy. Three fundamental services (Compute, Storage, and Database) are offered to developers to satisfy the basic needs of developing cloud applications. Additionally, with Windows Azure services, (Building Blocks Services, Data Services, Networking, and Marketplace) developers will find it increasingly easy to develop rich and powerful applications. The foundations of this cloud offering are robust and we should continue to look out for new features to be added to this platform.

References

This article was written using the following resources as references:

• Windows Azure Platform Training Kit
• https://www.windowsazure.com/en-us/home/tour/overview/
• http://azurebootcamp.com/

This post was also published at A Cloud Place blog.

As we know XML is a popular file format and standard that has been used for many purposes in the IT industry. Starting from storing configuration file, storing data, transferring via web service, and so many more.

Nonetheless, I believe most of you have ever got frustrated with editing and manipulating XML document.

Recently, I have been introduced to try out a powerful XML editor, Liquid XML Studio. In fact, it is more than an editor. Liquid XML Studio comes with the following features:

• XML Schema Editor
• XML Data Binding Code Generator
• XML Data Mapper
• WSDL Editor
• XML Editor
• Microsoft Visual Studio Integration (2005, 2008, 2010)
• Web Service Test Client
• XPath Expression Builder
• HTML Documentation Generation
• XSLT Editor & Debugger
• XQuery Editor & Debugger
• Large File Editor
• XML Diff – Compare XML Files

Check out this link http://www.liquid-technologies.com/xml-studio.aspx for more detail of Liquid XML Studio!

Windows Azure is the Microsoft cloud computing platform which enables developers to quickly develop, deploy, and manage their applications hosted in a Microsoft data center. As a PAAS provider, Windows Azure not only takes care of the infrastructure, but will also help to manage higher level components including operating systems, runtimes, and middleware.

This article will begin by looking at the Windows Azure data centers and will then walk through each of the available services provided by Windows Azure.

Windows Azure Data Centers

Slide 17 of WindowsAzureOverview.pptx (Windows Azure Platform Training Kit)

Microsoft has invested heavily in Windows Azure over the past few years. Six data centers across three continents have been developed to serve millions of customers. They have been built with an optimized power efficiency mechanism, self-cooling containers, and hardware homogeneity, which differentiates them from other data centers.

The data centers are located in the following cities:

• US North Central – Chicago, IL
• US South Central – San Antonio, TX
• West Europe – Amsterdam
• North Europe – Dublin
• East Asia – Hong Kong
• South-East Asia – Singapore

Windows Azure data centers are vast and intricately sophisticated.

Images courtesy of Microsoft http://azurebootcamp.com

Windows Azure Services

Having seen the data centers, let’s move on to discuss the various services provided by Windows Azure.

Microsoft has previously categorized the Windows Azure Platform into three main components: Windows Azure, SQL Azure, and Windows Azure AppFabric. However, with the recent launch of the Metro-style Windows Azure portal, there are some slight changes to the branding, but the functionality has remained similar.  The following diagram illustrates the complete suite of Windows Azure services available today.

The complete suite of Windows Azure services available today

A. Core Services

1. Compute

The Compute service refers to computation power, usually in the form of provisioned Virtual Machines (VMs). In Windows Azure, the compute containers are often referred to as ‘roles’. At the moment, there are three types of roles:

(i) Web Roles

Web Roles offer a predefined environment, set-up to allow developers to easily deploy web applications. Web server IIS (Internet Information Services) has been preinstalled and preconfigured to readily host your web application.

(ii) Worker Roles

Worker Roles allow the developer to run an application’s background processes that do not require user interface interaction. Worker Roles are perfectly suitable to run processes such as scheduled batch jobs, asynchronous processing, and number crunching jobs.

(iii) VM Roles

VM Roles enable developers to bring their customized Windows Server 2008 R2 VM to the cloud, and configure it. VM Roles are suitable for cases where the prerequisite software requires lengthy, manual installation.

Using VM Roles has one substantial drawback. Unlike Web Roles and Worker Roles, whereby Windows Azure will automatically manage the OS, VM Roles require developers to actively manage the OS.

Apart from ‘roles’, there are two other essential terms, namely ‘VM Size’ and ‘Instance’.

• VM Size denotes the predefined specifications that Windows Azure offers for the provisioned VM. The following diagram shows various Windows Azure VM Sizes.

Slide 21 of WindowsAzureOverview.pptx (Windows Azure Platform Training Kit)

• Instance refers to the actual VM that is provisioned. Developers will need to specify how many instances they need after selecting the VM Size.

2.     Storage

Windows Azure Storage is a cloud storage service that comes with the following characteristics:

• Highly available with 99.9% monthly SLA
• Scalable with automatic load-balanced partitioning
• Data is replicated for resilience and protection with 3 copies within the same data center,  and another 3 copies geo-replicated in another data center
• Accessible through several libraries including .NET, Java, PHP, Ruby, etc. REST-based API
• Up to 100TB size limit per storage account
• Cost effective
  • Storage capacity: $ 0.14 per GB per month
  • Storage transaction: $ 0.01 per 10,000 transaction

The first step in using Windows Azure Storage is to create a storage account by specifying storage account name and the region:

There are four types of storage abstraction that are available today:

(i) BLOB (Binary Large Object) Storage

Blob Storage provides a highly scalable, durable, and available file system in the cloud. Blob Storage allows customers to store any file type such as video, audio, photos, or text.

(ii) Table Storage

Table Storage provides structured storage that can be used to store non-relational tabular data. A Table is a set of entities, which contain a set of properties. An application can manipulate the entities and query over any of the properties stored in a Table.

(iii) Queue Storage

Queue Storage is a reliable and persistent messaging delivery that can be used to bridge applications. Queues are often being used to reliably dispatch asynchronous work.

(iv) Azure Drive

Azure Drive (aka X-Drive) provides the capability to store durable data by using the existing Windows NTFS APIs. Azure Drive is essentially a VHD Page Blob mounted as an NTFS drive by a Windows Azure instance.

3.  Database

SQL Azure database is a highly available database service built on existing SQL Server technology. Developers do not have to setup, install, configure, or manage any of the  database infrastructure. All developers need to do is define the database name, edition, and size. Developers are then ready to bring the objects and data to the cloud:

SQL Azure uses the same T-SQL language and the same tools as SQL Server Management Studio to manage databases.  SQL Azure is likely to lead to a shift in the responsibility of DBAs toward a more logical administration, as SQL Azure handles physical administration. For example, a SQL Azure database will be replicated to three copies to ensure high-availability.

Although some variations exist today, Microsoft plans to support the features unavailable in SQL Azure in the future. Users can always vote and provide feedback to the SQL Azure team for upcoming feature consideration.

Coming up in my next article, I will carry on the discussion with the additional services that Windows Azure offers including ‘Building Block Services’, Data Services, Networking and more so make sure you keep an eye out for it because it’s coming soon!

This post was also published at A Cloud Place blog.

In my previous article, I discussed the basic concepts behind Cloud Computing including definitions, characteristics, and various service models. In this article I will discuss service models in more detail, and in particular the comparison between IAAS and PAAS from a developer’s standpoint.

I’m using two giant cloud players for illustrative purposes: Amazon Web Service representing IAAS and Windows Azure Platform representing PAAS. Nonetheless, please be informed that the emphasis is on the service models and not the actual cloud players.

Figure 1: IAAS VS PAAS

Infrastructure as a Service (IAAS)

IAAS refers to the cloud service model that provides on-demand infrastructure services to the customer. The infrastructure may refer to rentable resources such as computation power, storage, load-balancer, and etc.

As you can see on the left-hand side of Table 1, the IAAS provider will be responsible for managing physical resources, for example network, servers, and clustered machines. Additionally, they typically will also manage virtualization technology enabling customers to run VMs (virtual machines). When it comes to the Operating System (OS), it is often arguable whether it’s managed by the provider or customer. In most cases, the IAAS provider will be responsible for customer VM Images with a preloaded OS but the customer will need to subsequently manage it. Using AWS as an example, AMI (Amazon Machine Image) offers customers several types of Operating Systems such as Windows Server, Linux SUSE, andLinux Red Hat. Although the OS is preloaded, AWS will not maintain or update it.

Other stacks of software including middleware (such as IIS, Tomcat, Caching Services), runtime (JRE and .NET Framework), and databases (SQL Server, Oracle, MySQL) are normally not provided in the VM Image. That’s because the IAAS provider won’t know and won’t care what customers are going to do with the VM. Customers are responsible for taking care of them. When all of the above mentioned software has been settled, customers will finally deploy the application and data on the VM.

Step-by-step: Setting-up an Application on IAAS Environment

To convey a comprehensive explanation, I am going to illustrate the steps involved when setting up an application in an IAAS environment. For that, I’m borrowing a slide from a presentation by Mark Russinovich, at the BUILD conference. This illustration explains how a typical IAAS provisioning model works.

Figure 2: Setting up an App

Considering a common scenario when you have finished developing a multi-tier application, you as the developer will need to deploy it to the cloud. The application will need to be hosted on a Web Server and an RDBMS database. For IAAS, here are the typical steps:

1.       Preparing Database Servers

Select the VM Images from the VM Images library. The VM Image will then get provisioned and launched. If DBMS software is not provided, you will need to install DBMS on your own.

2.       Preparing Web / Application Servers

Select VM Images from the library to get provisioned and launched. If the web/app server/runtime aren’t installed, you’ll need to install them by yourself.

3.       Provisioning a Database and Its Objects

The next step is about provisioning the database, including configuring the data files, log files, security, etc. Then you create the tables and add data to it.

4.       Deploying Your Application

Next you take the application that you’ve developed and deploy it to the Web Server.

5.       Configuring load-balancer

When you need to host your application on multiple instances, you may also need to configure things such as the IP Address for each instance and load balancer.

6.       Managing Your VMs and DMBS

The final step is about managing the VMs. For example, when there’s an update or service pack on the OS, the IAAS provider will not automatically do it for you. Instead, you may need to do it by yourself.

Platform as a Service (PAAS)

Now, let’s jump into another cloud spectrum, “PAAS”, to see how it differs. In PAAS, the provisioning model is about an on-demand application hosting environment. Not only managing the component like an IAAS provider would, a PAAS provider will also help customers manage additional responsibilities such as OS, Middleware, Runtime, and even Databases, as can be seen on the right-hand side of  Table 1.

In other words, you can think of PAAS as renting a stack of software, hardware, and infrastructure. Customer will just need to bring the application and data and they are ready to go.

Step-by-step: Setting-up an Application on PAAS Environment

For PAAS, given that the database server, VM, and web server VM are readily provisioned, you just need to do two steps, as illustrated by another slide from Mark Russinovich.

Figure 3: Provision and Deploy

1.       Database Provisioning

You might need to indicate where (which region) your virtual DB Server is provisioned, but you don’t have to install a bunch of DBMS software on your own. You will need to provision the database, create tables, and add data.

2.       Deploying Your Application

This is a similar step applicable to IAAS, you will still need to deploy your application on the PAAS cloud environment.

How about the load-balancer? Take Windows Azure as example, it will all automatically be configured and ready to take the traffic, and everything else will be automatically managed. You don’t have to worry about IP Addresses or a load-balancer.

How about maintaining VMs? The DBMS and Web Server VM will be maintained by the provider. For example:

• If the VM where your application is hosted has any hardware issues, the provider should be able to detect the failure and rectify it immediately to make sure that your application will stay up and running. In Windows Azure, Fabric Controller will be the component handling these kinds of issues.
• If there are new updates or patches on the Operating System, the provider will make sure that the VM your application sits on is always updated. For example: Windows Azure uses “Guest OS Version” to differentiate service updates. Of course you can also choose to stick to one version or auto-update.

Figure 4: Configuration

Summary

To summarize, we have investigated different service models and provisioning steps of IAAS and PAAS solutions. PAAS providers indeed take on much more responsibility for your solution than an IAAS provider would. On the other side, IAAS may offer more flexibility at lower level (example: public IP addresses, load-balancer, etc.).

There’s no one-size-fits-all here. As a developer or architect, you should understand a customer’s need and determine the correct model to get the best possible outcome.

This post was also published at A Cloud Place blog.