使Go Webapp独立于Google App Engine

Question

This question comes from working on my webapp, a feed reader written in Go. The code is available at http://github.com/matthewbauer/rivulet although that should not be necessary to answer the question.

I have a webapp written in Go that is running on Google's App Engine. It uses the usual common App Engine libraries like datastore, memcache, and user.

Is there any way to let my users run this app on their own without breaking App Engine compatibility?

Go now provides build constraints that exclude/include files based on target build platform:

// +build !appengine

So, I know that this is possible. But, my biggest problem is with my libraries that depend on App Engine: datastore, memcache, and user. I know other libraries provide datastore and memcache, and I can implement user on my own, but how would I go about wrapping it up?

I know that I can have them set up a development server with the SDK, but that might be too involved for some users. I want a single executable that normal Go projects provide. IS that possible?

If any examples exist, I haven't found them yet; any examples of App Engine independent webapps would be appreciated. I can learn by example.

Answer 1

You will probably have refactor your code.

The basic rule of thumb will be anywhere you depend on an AppEngine package define your own interface for the way you use it. This will allow you decouple the app from the appengine libraries.

Once you've defined those interfaces then you can start providing alternatives that satisfy the interfaces. You'll be able to plugin any Datastore or Memcache that satisfies the interfaces and your app will be able to both run on appengine or as a standalone with the alternatives.