Many people are surprised to hear that running Java on Windows Azure is even possible, but there are already large Java-based financial services and scheduling applications running in production.
Microsoft has committed to making Java a “first class citizen on Windows Azure”. In this article I explore the motivations behind Java on Windows Azure and weighs up the pros and cons.
Why choose Windows Azure?
Java has been a popular platform for Enterprise development for over ten years. Many organisations have large investments in Java code with applications representing hundreds of man years of development.
Java applications can be difficult and expensive to host, needing dedicated servers and data centre resources. Cloud computing can help to simplify and consolidate IT infrastructure and there are large potential cost savings in moving to the Cloud.
With the demise of Sun Microsystems, Windows Server and SQL Server have become a common choice of hosting platform. Windows Azure and SQL Azure can be a natural next step.
Java web applications
Typically Java web applications are implemented using servlets and/or Java Server Pages running in a servlet container such as Tomcat, JBOSS or Jetty.
[AzureRunMe] is also a popular choice because it provide a more general purpose, customisable and extensible framework. It works with a variety of technologies and application frameworks.
Cloud based web applications should ideally be stateless, but Java applications often use shared session state. One approach is to use the Atomus TomcatAzureSessionManager which persists session information to Windows Azure table storage.
Sticky sessions are not supported on Windows Azure (they inhibit horizontal scale out) but there are some workarounds, including Ryan Dunn’s [Windows Azure Sticky HTTP Session Router]. Optionally, IIS Application Request Routing can be used as a reverse proxy in front of your web application to provide additional security.
Java applications are encouraged to be database agnostic, so moving to Microsoft’s SQL Azure database-as-a-service offering can be as straightforward as changing a JDBC driver. The Microsoft JDBC Driver now officially supports SQL Azure. Most SQL Server databases can be moved to SQL Azure with tools such as the SQL Azure Migration Wizard. I’ve also seen successful conversions from MySQL.
Windows Azure Storage includes blobs, tables and queues. All are available programmatically using the Windows Azure SDK for Java.
Blobs are often a cheap and scalable alternative to file storage for documents, and can easily be incorporated into the Windows Azure CDN.
Tables can be a cheaper and more scalable alternative to relational databases for tabular data.
Queues are a useful way to distribute work to worker roles.
It is technically possible to develop Azure applications on Mac OS X or Linux, but it’s still easier to use a Windows machine for build and packaging. The Windows Azure management portal requires Silverlight and seems to work best in Internet Explorer.
Microsoft and Soyatec have provided the Windows Azure Tools for Eclipse.
If you are familiar with PowerShell, then the Windows Azure Platform PowerShell Cmdlets are useful management and administration tools.
If you prefer a GUI, then I recommend the Cerebrata tools.
What are the cons?
At the time of writing, the maximum size of a SQL Azure database is 50 GB – Not a huge amount for an enterprise application.
You're only allowed five external TCP ports per VM in your service definition. [This has recently changed to 25 - see Microsoft's announcement.] Many Java stacks use ports liberally for everything from JMX, JCA, clustering etc.
You can’t use the Windows Azure AppFabric Cache service yet – there is no suitable API for Java.
You need to be careful about IP address configuration in your application stack and understand the way that the Windows firewall works.
It’s still hard to get support from Java vendors who question whether Windows Azure is the same as Windows Server.
Embracing the cloud
Moving your Java application to the cloud is just the first step. To really benefit from cloud economics you need to make use of cloud features and cloud architecture. A small amount of rework in your application can often allow better scale out and better use of smaller, cheaper Virtual Machines.
The Windows Azure APIs and libraries allow you to access cheaper and more scalable storage (blobs, tables and queues) as well as features such as the Windows Azure Content Distribution Network (CDN). The Windows Azure AbbFabric provides cloud based middleware services that make it easier to build hybrid cloud / on-premises solutions.
Microsoft is clearly committed to interoperability on the Windows Azure Platform, and support for Java in particular. Java on Windows Azure not only works, but can form part of a cost effective strategy for Java applications.
Rob Blackwell is R&D Director at Two10degrees, a UK based Microsoft Partner specialising in Windows Azure architecture and software development.