How do I move instances from one project to the next?
Problem: I have frontend production instance and backend production instance in 2 separate project. I would like to have my production instances (both frontend and backend) in the same project.
How do I move instances from one project to the next within Google App Engine?
You could have the 2 apps run as 2 separate services inside the same project. To do that you'd have to deploy the app from the project that will disappear as another service in the project that will remain. Some code changes might be required, depending on how the app is coded. Typically they're small changes, though.
IMHO it would be simpler to keep the project currently hosting the frontend and move the backend over from the project to be retired. The reason is that the frontend is typically better fitted to play the default service role and it is already setup as such, changes should be smaller. Performing the move in the other direction would mean both services would need to changed.
You might need a dispatch.yaml file to route incoming packets, unless the URL mappings of the services are really well done. Not a big deal.
If you're using custom domains, with a bit of care it is possible to make the move (almost) transparent - by having the new service up and running before retiring the old project. DNS propagation time becomes rather irrelevant - both old and new services being simultaneously ready during the transition.
Note: technically you wouldn't be "moving" instances, you'd just stop the ones serving the project to be retired and start new ones for the service added to the project to be kept.
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