feat: support managing cluster resources in a namespaced mode

[alexmt]

Signed-off-by: Alexander Matyushentsev AMatyushentsev@gmail.com

Closes #4502
Depends on argoproj/gitops-engine#297

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PR introduces an additional setting that enables managing cluster-level resources of a cluster in a namespace mode.
The main use case is k8s cluster addons management when one Argo CD deploys platform level app (e.g. ingress controller, argo rollouts/workflows ) into multiple clusters. In this case, Argo needs to manage resources in 2~3 namespaces and CRDs. So it is beneficial to "watch" only some namespaces instead of whole cluster + cluster level resources.

Three additional CLI commands had been added to argocd-util:

• argocd-util cluster namespaces - prints list of clusters and namespaces managed in each cluster

argocd-util cluster namespaces
CLUSTER                         NAMESPACES
https://kubernetes.default.svc  dex,argo,argocd,default (total 15)

• argocd-util cluster namespaces enable-namespaced-mode - switches clusters into namespaced mode

# switch all clusters with 2 or less managed namespaces into namespaced mode
argocd-util cluster namespaces enable-namespaced-mode '*' --cluster-resources --max-namespace-count 2

• argocd-util cluster namespaces disable-namespaced-mode - disables namespaced mode

# disable namespaced mode for all clusters
argocd-util cluster namespaces disable-namespaced-mode '*'

[codecov]

Codecov Report

Merging #6581 (04e2782) into master (8030f42) will decrease coverage by 0.31%.
The diff coverage is 2.89%.

@@            Coverage Diff             @@
##           master    #6581      +/-   ##
==========================================
- Coverage   41.30%   40.98%   -0.32%     
==========================================
  Files         156      156              
  Lines       20702    20865     +163     
==========================================
+ Hits         8550     8552       +2     
- Misses      10944    11103     +159     
- Partials     1208     1210       +2     

Impacted Files	Coverage Δ
cmd/argocd-util/commands/cluster.go	0.00% <0.00%> (ø)
cmd/argocd/commands/cluster.go	2.59% <0.00%> (ø)
controller/cache/cache.go	10.62% <0.00%> (-0.12%)	⬇️
pkg/apis/application/v1alpha1/types.go	57.71% <0.00%> (-0.18%)	⬇️
server/cluster/cluster.go	17.54% <0.00%> (-0.32%)	⬇️
util/db/cluster.go	59.52% <33.33%> (-0.48%)	⬇️
cmd/util/cluster.go	40.00% <80.00%> (+0.31%)	⬆️
util/settings/settings.go	47.00% <0.00%> (ø)

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[alexmt]

@jessesuen can you take a look please?

[jannfis]

I'm wondering what exactly is the benefit of this mode? Will Argo CD still have to have full cluster level permission for this to work? Is the only benefit that we'd need to watch for changes on less namespaces, as opposed to watch for changes on all namespaces in the cluster?

[alexmt]

@jannfis , this change is mostly about performance: Argo CD might be configured to "watch" some namespaces and cluster level resources. This is beneficial if Argo CD is used to manage 1~2 namespaces + CRDs in hundreds of clusters.

Additionally full cluster permissions are not required. Admin can provide token that has permissions to required cluster level resources only and required namespaces. Other cluster level resources can be excluded using resource exclusions.

[mayzhang2000]

LGTM

[alswl]

Great Job, Argo CD lister pager is using hundred of memory in my situation. But in the previous version, cluster namespaces cannot using because it ignores the white space(none namespaced namespace). I will try the 2.1 version.