GAE instance is serving on different url

Question

My google app engine instance is serving on different url than the default's one. Recently I uploaded an GAE project to the newly created instance of code foo-backend.

On seeing the serving logs, it shows

> /_ah/spi/BackendService.getApiConfigs
Saved; key: __appstats__:031500, part: 57 bytes, full: 1452 bytes, overhead: 0.000 + 0.003; link: http://1-dot-foo-backend.appspot.com/_ah/stats/details?time=1479812131572

You see, serving url is http://1-dot-foo-backend.appspot.com instead of http://foo-backend.appspot.com. I want to change this.. Any idea?

Answer 1

In your app.yaml you have version: 1.

To see the 'why' of what's going on here, consider the following scenario: You have version n of your app deployed, with the front-end queuing work for the back-end. You deploy version n+1 and make it the default. But you made a coordinated change between front-ends and back-ends. What now happens if work queued by front-end version n is received by a version n+1 backend? Depending on the change, it might cause mayhem.

The only safe thing to do is to arrange for work queued by a version n front-end to be handled by a version n back-end until all version n work is drained. Meanwhile work queued by a version n+1 front-end get handled by a version n+1 backend. How does this be guaranteed? By encoding the default version at the time the work is queued in the URL.