How do you upgrade/deploy to the latest version of Google App Engine (SDK)?

I have developed a GAE application on version 1.5.0 of the SDK. It is already deployed to http://linkpad.me and working properly (as of this writing). I am wondering how the upgrade process should go to get to version开发者_JAVA技巧 1.5.1 of the GAE SDK.

As far as I can tell, I should do the following:

1. Download version 1.5.1 of the SDK
2. Test my application locally using version 1.5.1 to make sure it still works
3. Deploy my application

Does my application start using version 1.5.1 of GAE once I do a deploy from v1.5.1 of the SDK?

Or do I need to switch to 1.5.1 using something like the App Engine Dashboard?

Is it possible to stay with version 1.5.0 indefinitely if I never download or use SDK version 1.5.1? (I imagine this would be a bad idea)

Your application started using 1.5.1 as soon as Google deployed it to production. There's no way for you to control which version the production servers use; they'll all upgraded at the same time.

Is it possible to stay with version 1.5.0 indefinitely if I never download or use SDK version 1.5.1? (I imagine this would be a bad idea)

Yes, it's possible. But it would be bad idea, because essential components of the cloud are being updated all the time. And you can probably miss critical updates or stuck with obsolete facilities of your local GAE server. For example, servlet container (Jetty), hadn't supported JavaEE 6 before it updated to 8.x version.