Side Menu Cluster List `clusters` performance badly at scale

[richard-cox]

SURE-7040

Setup

• Rancher version: 2.9.1 (and before)

Describe the bug

• When there are lots of clusters (~700) logging in takes a number of seconds
• Some of this is generic processing of a large number of resources (objectify, cache, etc), however some specific to the top level menu
  • Once the resources are fetched we spend ~3 seconds processing resources
  • 
• Of the 3 seconds process we spend over 1 second in a top level menu computed property clusters
  • 
• In clusters we iterate over all clusters a number of times. We also convert them to an object ready to show on screen.
• This will in theory go away with vai (we shouldn't ever fetch that many resources). Until then...
• Suggestion 1
  • recreating the issue
  • only map the objects we're going to show on screen, this could be a very small number
  • attempt to reproduce with fix
• Suggestion 2
  • less loops!

Note - clusters runs often, perhaps on cluster state change? each time it consumes over second of cpu

To Reproduce

• Load ~700 clusters (they could be RKE2 Custom)
• refresh on login page
• log in

Result

• should in theory be a large time spent in clusters

Expected Result

• almost no time in `clusters

Additional context

• If vai changes have merged this file will have already been reworked

[richard-cox]

/backport v2.9.3

[richard-cox]

Note - https://github.com/rancher/dashboard/pull/11998 contains a 2.9.3 fix