Proposal: Allow negative/inverse selection for label and resource selectors

[jgn-epp]

Summary

When using the argocd app wait and argo app sync commands, it is possible to use the -l / --selector parameter filter based on labels and their values. It is also possible to use the --resource filter to only target certain types of resources. Unfortunately it is (as far as I can tell) not possible to do negative/inverse selection on these - for example so that you could filter out resources with a certain label or of a certain type.

Motivation

As part of our deployment pipeline, we have a step where we use argocd app wait <appname> --health --sync, but the process sometimes gets stuck because of objects in the deployment that continually mark their health as Progressing and are not always necessary to wait for. I would like to be able to easily filter these objects out of the argocd app wait call, but as only positive selection is possible, I would have to either:

• Tag everything that I want to wait for and use the -l parameter to select those resources. I would like to avoid this since that means adding a label to every single resource besides that particular one that I am trying to avoid.
• Use the --resource parameter for every possible resource that is NOT the type of resource that I want to filter out. I would like to avoid this since that means I would have to include every type of resource in use now and it would need to be updated if custom resources are introduced to make sure they are included.

Proposal

I would like the -l / --selector to allow negative/inverse selection, example:

• argocd app wait <appname> -l label_example!=hello

Additionally/alternatively it would also be nice if the --resource parameter allowed some kind of negative/inverse selection, example:

• argocd app wait <appname> --resource :!ResourceToFilterOut:

[crenshaw-dev]

Looks like kubectl supports this. It would be nice to have feature-parity with kubectl. https://stackoverflow.com/a/58936877/684776

[maheshbaliga]

Hi @crenshaw-dev. I would like to attempt this one. Could you please assign this to me? I'm working on -l / --selector part of this issue and the fix is ready, will submit a PR very soon.

[maheshbaliga]

Hi @crenshaw-dev, can you please review PR #10729 and let me know if any changes are required.

[maheshbaliga]

Hi @crenshaw-dev. Are we looking at implementing the --resource filtering as well? If yes, which wildcard characters should be supported apart from ! negation?

Currently, looks like the resources are selected only if it matches all the criteria - Group, Kind & Name (Namespace, if specified). Filtering based on apps:Deployment:guestbook-ui works, but :Deployment: or :Deployment:guestbook-ui doesn't. Should a blank value be supported in Kind & Name as well?

[crenshaw-dev]

@maheshbaliga I think that could make an excellent follow-up PR! I think just supporting a negate-able glob pattern would be fine (similar to what's available for destinations in the AppProject CRD). Maybe a negate-able glob pattern with : as the separator. So @jgn-epp's pattern would be !*:ResourceToFilterOut:*.

[maheshbaliga]

Hi @crenshaw-dev. Since --resource can be specified repeatedly, they currently act as OR conditions. The resource has to satisfy one of the filters.

Is the same behaviour expected with the inclusion of ! too? If yes, argocd app wait guestbook --resource '!*:Deployment:*' --resource '!*:Service:*', will wait for both Deployment & Service. Is this behaviour OK?

[crenshaw-dev]

That seems like the most intuitive behavior to me. :-)

[maheshbaliga]

Hi. I've almost completed --resource part of this issue, will submit a PR very soon.

[maheshbaliga]

Hi @crenshaw-dev, can you please review PR #10893 and let me know if any changes are required.