Ensure we use the least amount of http Clients possible

[sbueringer]

What would you like to be added (User Story)?

In CR v0.15 there was a change which allows us to reduce the amount of http Clients used and thus the amount of TCP connections.

Let's take a look at our controllers and see if we can further optimize.

Detailed Description

Anything else you would like to add?

No response

Label(s) to be applied

/kind feature
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[sbueringer]

/triage accepted
/assign

[fabriziopandini]

is there a link or some more info about the CR change?

[sbueringer]

PR: kubernetes-sigs/controller-runtime#2122

Draft release notes:

• Make *http.Client configurable and use/share the same client by default (📖 Update README to point to 2020 meeting notes. #2122)
  • When using the default Manager configuration, no immediate changes are needed.
  • client/apiutil.NewDynamicRESTMapper signature has changed and now requires an *http.Client as parameter.
  • cluster.Cluster interface requires GetHTTPClient() method which must return an already configured, non-nil, *http.Client for the Cluster. When using cluster.New to create Clusters, the client is created internally if not specified as an Options field.
  • cluster.Options.MapperProvider field now requires a *rest.Config and *http.Client.

I already partially implement this in my bump PR. I just want to check (also in the context of scale testing) if it can be improved a bit more.

[fabriziopandini]

/priority important-longterm