Ideas for how to do an optional backup?

[justinclift]

At present, the docker container does an in-place upgrade, with no capability for backing things up (just in case).

We should probably support some kind of useful, optional, backup capability.

So far, my initial thinking is to have some environment variable to define a new mount point (PGAUTO_BACKUPDIR or similar), and if that's set to a valid value pointing at an empty directory then we use it.

For the backup type, I reckon we should just go with a "full data copy" approach rather than a pgdump. At least for now.

It should (in theory) be reasonably simple. We'd use that "backupdir" as part of the pg_upgrade file moving process, running the pg_upgrade without the --link option so things aren't upgraded in place.

That way, the backup gets done, and the new database ends up in the correct directory. The downsides are the (potentially significant) extra space that gets used, and the extra time the whole upgrade process will take.

Optimally, we'd probably recommend people use a 2nd bind mounted directory for that "backupdir", so it's not a backup that disappears when the container stops.

Thoughts? 😄

[brbrown25]

I think it makes sense to have a backupdir option and maybe an auto recover option, so if the upgrade fails it restores the backup into the original location.

[justinclift]

Interesting idea. Yeah, it probably wouldn't be too hard automatically recover the original data back to the starting location.

It'll take some more detailed thinking about when coming to implement it. 😄