When checking for node limit getting exceeded the pod eviction
never fails. Thus, ignoring the metric reporting when a pod fails
to be evicted due to node limit constrains.
The error also allows plugin to react on other limits getting
exceeded. E.g. the limit on the number of pods evicted per namespace.
* feat: profile name for pods_evicted metric
Support new label "profile" for "pods_evicted" metric to allow
understand which profiles are evicting more pods, allowing better
observability
* refactor: evictoptions improved observability
Send profile and strategy names for EvictOptions, allowing Evictors to
access observability information
* cleanup: remove unnecessary evictoption reference
* feat: evictoptions for nodeutilzation
Explicit usage of options when invoking evictPods from the helper
function from nodeutilization for both highnodeutilization and
lownodeutilization
* feat: Implement preferredDuringSchedulingIgnoredDuringExecution for RemovePodsViolatingNodeAffinity
Now, the descheduler can detect and evict pods that are not optimally
allocated according to the "preferred..." node affinity. It only evicts
a pod if it can be scheduled on a node that scores higher in terms of
preferred node affinity than the current one.
This can be activated by enabling the RemovePodsViolatingNodeAffinity
plugin and passing "preferredDuringSchedulingIgnoredDuringExecution" in
the args.
For example, imagine we have a pod that prefers nodes with label "key1:
value1" with a weight of 10. If this pod is scheduled on a node that
doesn't have "key1: value1" as label but there's another node that has
this label and where this pod can potentially run, then the descheduler
will evict the pod.
Another effect of this commit is that the
RemovePodsViolatingNodeAffinity plugin will not remove pods that don't
fit in the current node but for other reasons than violating the node
affinity. Before that, enabling this plugin could cause evictions on
pods that were running on tainted nodes without the necessary
tolerations.
This commit also fixes the wording of some tests from
node_affinity_test.go and some parameters and expectations of these
tests, which were wrong.
* Optimization on RemovePodsViolatingNodeAffinity
Before checking if a pod can be evicted or if it can be scheduled
somewhere else, we first check if it has the corresponding nodeAffinity
field defined. Otherwise, the pod is automatically discarded as a
candidate.
Apart from that, the method that calculates the weight that a pod
gives to a node based on its preferred node affinity has been
renamed to better reflect what it does.
