package search: Add repository queryparam which invokes dnf-json

[croissanne]

Instead of #244:

• keep the package lists for the predefined repos
• expand /packages to take ?repo= as well, which would invoke dnf-json and search in that repo

This would give package search for non-predefined repos.

[teg]

We should be careful about how this would perform, but overall: I like!

[croissanne]

Yea the assumption is that this would be slow. There's a few options here though:

Get the entire package list? Currently you need to specify search as well, but we could change it to take * or something and it would give you all packages. Edge/fleet mgmt could grab the list once and store it for x amount of time?

We could generate the json blob and store it for x amount of time as well?

[teg]

If we go down this path, we should make dnf-json into a daemon, and pin the caches, that should at least avoid the 1.5s overhead per request. It might then be that (the correct) search is quick (much quicker than depsolving), so this might not be a big problem. Another option would be to make I package searching API, separate from image builder (this really has nothing to do with the rest of the API).

[croissanne]

Hm I'm not entirely sure I follow. /packages is something that the frontend needs for sure (not for 3rd party repos but still), so why doesn't it belong here?

[teg]

I mean it could be in a separate API, as it does not speak to composer, it does not use the database and the compose API could be used without it. It could also be used independently of image-builder. dnf-as-a-service, if you wish ;) The benefit would be (albeit minimal), that if this gets overloaded it would not affect regular operations. That might be overkill though, just a thought.