Best practice for updating silverlight deployment that is actively being used

Question

I am currently running a SL3 project where we are in a highly iterative development mode with about 25 active test customers. I am making small changes at a clip of about 4 new builds per day. It is important to know this application is mission critical line of business for these 25 people, it is the tool they use all day to do their work so they are using it constantly and often launch their browser and the app in the morning and never close it until the end of the day.

The challenge is that when I make an update to the application I have no clean way to notify the users, in most cases this is ok as it is rare that I introduce a data contract change or something that would be a classic 'breaking' change to the app/service. Users keep plugging along and will get the change next time they refresh.

Right now we have resorted to emailing everyone and telling them to force refresh or close the browser and log back in.

Surely there is a better way...

Right now my train of thought is to have a method on the server that compares client xap versions and determines if the client being used is the most up to date, if so I will notify the user and make them update.

What have you done to solve this problem?

Answer 1

One way of doing it is to use a push mechanism (I used Kaazing Websoocket Gateway but any would do). When a new version of the XAP is released a message (either manually entered into the system by admin or automated triggered by XAP file change event) would be sent to all the clients. In the simplest scenario some notification would be shown to a user (telling him that a new version is released and the application needs to refresh) and then the app would refresh (by simply reloading the page) saving user's state if necessary.

Answer 2

If I would do this I would just keep it simple. A configuration value in web.config and a corresponding service method that simply returns that value (the value itself could be anything, but a counter is probably wise). Then you could have your Silverlight app poll that service method at regular intervals. Whenever the value changes (which you would do manually when you deploy a new version), just pop up a dialog telling the user to refresh the browser or log in/out. This way you don't have to force them to refresh every time. If you go with the idea of comparing xap file versions they will always be required to refresh, even for non-breaking changes.

If you want to take it further you could come up with some sort of mechanism to distinguish between different severity levels. For instance, if the new config value would contain the string "update_forced", you could force the users to reload the app by logging them out automatically (a little harsh, perhaps). If it contains the string "update_recommended", just show a little icon at the top right corner saying that there is a new version and that they should upgrade in their own time.