PollingDuplex scaling in Windows Azure

SLWSTeam — Tue, 24 Nov 2009 19:58:58 GMT

One of the great sessions at this year’s PDC talked about a collaboration between Invensys and Microsoft’s DPE team to build a solution that can deliver energy pricing information to a variety of clients, using a duplex message pattern.

Effectively Invensys used a WCF service hosted in a Windows Azure web role to tunnel bi-directional HTTP traffic from the Windows Azure platform AppFabric service bus capability to Silverlight clients. Unfortunately this workaround is needed since the TCP-based relay binding that service bus offers is not supported in Silverlight at this point.

Once Invensys was using PollingDuplex in Azure, they needed to scale to a large number of clients, so they needed to enable scale out between multiple web role instances. This capability is not available out-of-the-box in Silverlight 3, so some hackery was required, as described in these blog posts:

The relevant content starts at around minute 38 in the video below.

While getting PollingDuplex to scale in Azure in Silverlight 3 requires some manual steps, the team is considering supporting this scenario out-of-the-box in Silverlight 4. It is not available in Silverlight 4 Beta, but please use the comments to submit your feedback.

Thanks,
Yavor Georgiev
Program Manager

Using WCF services from Silverlight in Azure

SLWSTeam — Thu, 09 Apr 2009 02:15:00 GMT

With all the buzz around Windows Azure, you may have wondered how to host your Silverlight application in the cloud. Since Silverlight controls are essentially static content, hosting them is as easy as uploading some files to the cloud.

When it comes to building WCF services to provide data to your Silverlight control, the story gets a little more complicated. The fact that the Azure cloud is a load-balanced environment as well as the deployment mechanism for setting up a service in Azure pose some unique challenges to hosting WCF services.

To help with this, our team has posted a Code Gallery site with 3 Silverlight-specific samples that you can run in the cloud and also on your local machine. The samples exercise the following features:

Sample #2: binary encoding
Sample #4: message credentials authentication over HTTPS
Sample #5: duplex (server “push”)

The third example hosts our chat sample in Azure for a massively-distributed free-for-all chat experience, and you can try it here. Try opening up this link across multiple machines and browsers and watch them all chat together.

Which brings me to probably the most useful thing we published: a list of known issues with hosting WCF services and Silverlight clients in Azure. Check out this page, and especially the sections “Hosting WCF Services” and “Hosting Silverlight Clients”. The page contains some workarounds we gathered from across the web, and is guaranteed to save you a bunch of head-scratching if you try WCF on Azure for yourself.

Cheers,
-Yavor

Silverlight Web Services Team : azure

PollingDuplex scaling in Windows Azure

Using WCF services from Silverlight in Azure