Installing on scalable applications does not work as expected

[stevegriffiths]

I note from the docs that this cartridge has not been tested on scalable apps, but wanted to report that I could not get it to work correctly inside a scalable application.

What happens is the process of installing the cartridge within a scalable app causes a new gear to be added to the app (standard behaviour when cartidges are installed on scalable apps). The backup cartridge then only sees this new gear when it is installed, not the other gears within the application that actually contain the application code, database etc. Hence when the backup is run, it is effectively backing up it's own, empty gear.

The attached image shows the arrangement within the app after setup.

It's worth adding that because of this, presumably backup gear would also not see database cartridge gears or additional gears created by the HAProxy load balanacer as the application scales up.