Fix downsampling option in querier URL

[obiesmans]

Fixes #1463

• Downsampling option in Querier UI is now reflected in the URL.

Changes

Verification

[obiesmans]

Amended the pr to use camelcase and have a max_source_resolution in URL, as in the documentation.

[bwplotka]

Awesome, thanks. Generally, it looks ok, just @GiedriusS comments applies. (:

Have you verified Querier and checked if it works? (:

[GiedriusS]

Everything works, just those two comments and we should be good to go 😄

[obiesmans]

Thanks a lot for the review ! Sorry I didn't reply sooner, was off for a few days.
I pushed an update that addresses @GiedriusS comments.

I also ran into issues where the URL params format didn't allow for empty params.
I thought that correcting this would make maintaining against the upstream prometheus UI harder, so instead I put "auto" as keyword in the UI and normalized it back to an empty string when submitting the query. Is it OK with you ?

[bwplotka]

Generally good, last question hopefully (:

[bwplotka]

Quick silly question, why we remove selected here again? It changes what is by default set, right?

[obiesmans]

I think that which option is selected by default should be driven from the javascript only.
(same place where the other UI driving logic is).

It doesn't change, the default which is still "0s" if the parameter is not set :
https://github.com/thanos-io/thanos/pull/1562/files#diff-b1f64ac291243b832fd99d257dcb04feR47-R49

Let me know if you agree with this choice, or if I should add this back in the UI.

[GiedriusS]

Makes sense IMHO that we keep all of that logic together in that file instead of the HTML code, thanks for pointing this out!

[GiedriusS]

Played around with it and it works well. Thanks for this and sorry for the late answer!

[GiedriusS]

Also, double-checked the "instant query" side of this - everything should work well like before and now actually the user will be able to see that they are able to change this parameter -- it was "invisible" before.

[obiesmans]

Thanks a lot for taking the time to review this @GiedriusS !