Versioning in device/server development

I am working on device applications, 开发者_如何学Pythonthat we will deploy some minimum device specific code to the device, and this component will dynamically load the rest of resources (javascript, images, etc) from our backend server. That way we can upgrade the app more often without depending too much on the device upgrade. In a way, this is similar to some iphone developers who want to avoid the app approval cycle with faster upgrades.

The code in device should be able to detect new upgrades on the server code, but only to a point, when we need to upgrade the device code as well, so we can support phased roll-out (upgrade 10% of devices at a time, etc).

I am sure some folks have already done this. Could you share your thinking and best practices on this?

One way would be for the application to have a polling process that asks a server if there is a new version of a particular resource.

The server then has complete control over who gets the upgrades and who doesn't (part of the "phone-home" could include the current version), and that would allow you to enforce the "only X% of clients get upgraded" capabilities. You may also want to include the ability for things to get "downgraded" so that you can roll back if you see too many errors in the first 10%.

This is essentially what web browsers do when they have a resource in the cache but it may have been expired. They say "Hey, Server, I have this resource that I got from you at XYZ date. If it's changed, give me a new one, if not, let me know." and the server either sends back a "Hasn't Changed" response, or a "Here's the new one" response.