How do I get all available namespaces?

[madelaney]

I was looking over the pod example:

  let pods: Api<Pod> = Api::default_namespaced(client);
  for p in pods.list(&ListParams::default()).await? {
    info!("found pod {}", p.name_any());
  }

and I was curious if there was a way to get all of the namespaces in a similar fashion?

[clux]

make an Api on Namespace

let ns: Api<Namepace> = Api::all(client)
ns.list(...).await

[LennonChin]

but how do i get multiple specified namespaces?

[clux]

you can loop over the namespaces you want and create a Api::namespaced(ns_i, ...) inside the loop

...or, if you are just listing/watching from multiple given namespaces you can technically do a single Api::all and use do a api.list with a specific field selector (on ListParams) with "metadata.namespace=ns1,metadata.namespace=ns2,...". (that doesn't work for .get though - then you need an Api::namespaced)

EDIT: you can only list out the complement turns out. see optimization guide for selectors

[LennonChin]

Thanks for your help! Will this method of Api::all combined withListParams put pressure on APIServer? Will it only read the namespace data specified inListParams from APIServer, or read all namespace data and filter it on the client side?

[clux]

field selectors or label selectors will do filter-equivalents server-side, so should be better when possible.

the Api construct (and associated params) are meant to model what the apiserver supports so ~WYSIWYG. (conversely; jsonpath must be done client-side - you cannot specify jsonpath queries on ListParams because it's not part of the api)

[LennonChin]

Thank you for your answer, it's great!

[LennonChin]

you can loop over the namespaces you want and create a Api::namespaced(ns_i, ...) inside the loop

...or, if you are just listing/watching from multiple given namespaces you can technically do a single Api::all and use do a api.list with a specific field selector (on ListParams) with "metadata.namespace=ns1,metadata.namespace=ns2,...". (that doesn't work for .get though - then you need an Api::namespaced)

Unfortunately, after testing, list and watch do not support field selectors with multiple namespaces, and client-go does not support it either.

[SOF3]

Also note that (iirc) Api::all with field selectors requires a ClusterRole giving you access to list, while field selectors only require list access to a particular namespace, so you probably wanted to just do multiple Api::namespaced() anyway

[clux]

list and watch do not support field selectors with multiple namespaces

bah, i didn't know it didn't support listing the namespaces, because i use it for listing the complement :(

..you have to either exclude ala kubectl get svc -A --field-selector "metadata.namespace!=default,metadata.namespace!=kube-system" or build labels instead

have updated the optimization guide selector section to reflect this :(