[Fleet] Individual agent upgrade modal forbids downgrades, but bulk upgrade modal allows them

[kpollich]

In the bulk upgrade modal, we show lesser versions of the agent binary even if they can't be applied to a given agent, e.g.

We show version 8.2.1 here even though we don't support downgrades from 8.3.0 -> 8.2.1.

I don't think we will actually honor the downgrade here (@nchaulet I think you can confirm this), but should we filter the list of versions down to only supported upgrades for all selected agents?

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[joshdover]

I think this issue is less urgent than I originally thought. I must have been testing an older build because at one point I saw the ability to downgrade to any version as early as 7.17.0.

It seems now the issue is that if you select agents with a mix of different versions the minimum the modal allows you to upgrade is not >= the highest version in the selected agents.

[joshdover]

Actually I was able to reproduce this again. The agents I selected were all on 8.2.0 I was able to select all of these options instead of only being able to select 8.2.1, 8.3.0, and 8.3.1-SNAPSHOT

[jen-huang]

@nchaulet Could you take a look at this?

[nchaulet]

Looks like we do not validate version client side for bulk upgrade, but we do not perform downgrade server side, if the version is a downgrade we will return the agent as not upgradable.
I am not sure if we want to validate available version client side and how this will scale for example with a kuery with thousands of agent.
We may have to create a new endpoint to search for minimum version across agents if we want to have client side version validation.

[nchaulet]

@joshdover I just tested again and look at the code and we validate version and only show upgrade version client side if we do not pass a kuery (not using select all on multiple page) if you pass a kuery we do not validate version as it potentially do not scale with n agents, but downgrade will be ignored client side, does this work for you?

[joshdover]

if you pass a kuery we do not validate version as it potentially do not scale with n agents, but downgrade will be ignored client side, does this work for you?

@nchaulet Thanks for digging in here. Avoiding the perf cost makes sense. I think it'd be nice to have some sort of feedback in the UI that some agents were skipped, but I think it's lower priority.

I wonder if we should at least have some feedback if all of the agents in the kuery don't pass the validation. What happens today in that case?

[nchaulet]

@joshdover we already have some feedback of the agent that cannot be upgraded it's in toast notification like this

I am closing that issue for now, but feel free to reopen it if it's not good enough.