This is a minor refactor of PodEvictor to include evictLocalStoragePods as a
property (so that it doesn't need to be passed to each strategy function.) It
also removes ListEvictablePodsOnNode and extends ListPodsOnANode with an optional
"filter" function parameter, so that for example IsEvictable can be passed to it
and achieve the same results as the function formerly known as ListEvictablePodsOnNode.
This approach also now allows strategies to more explicitly extend their criteria of what
IsEvictable considers an evictable pod (such as NodeAffinity, which checks that the pod
can fit on any other node).
1.Set default CPU/Mem/Pods percentage of thresholds to 100
2.Stop evicting pods if any resource ran out
3.Add thresholds verification method and limit resource percentage within [0, 100]
4.Change testcases and readme
This increases the specificity of the RemoveDuplicates strategy by
removing pods which not only have the same owner, but who also
must have the same list of container images. This also adds a
parameter, `ExcludeOwnerKinds` to the RemoveDuplicates strategy
which accepts a list of Kinds. If a pod has any of these Kinds as
an owner, that pod is not considered for eviction.
The EvictPod function previously returned a bool and an error. The
function now only returns an error. Callers can check for failure by
testing if the returned error is not nil. This aligns the EvictPod
function with idiomatic Go best practices.
Also, the function name has been changed from EvictPod to evictPod
because it is not used outside the evictions package.
End users should be able to see the detailed error from the EvictPod
method when it fails. Updates all strategies to log the error. The
PodLifeTime strategy already logs this error.
In multi-tenant environments it is useful to know which namespace a pod
was evicted from. Therefore log the namespace when evicting pods.
Also, do not log a nil error when successfully evicting pods.
The new PodLifeTime descheduler strategy can be used to evict pods that
were created more than the configured number of seconds ago.
In the below example pods created more than 24 hours ago will be evicted.
````
apiVersion: "descheduler/v1alpha1"
kind: "DeschedulerPolicy"
strategies:
"PodLifeTime":
enabled: true
params:
maxPodLifeTimeSeconds: 86400
````
Each strategy implements a test for checking if a maximum number of pods per node
was already evicted. The test duplicates a code that can be put
under a single invocation. Thus, reducing the number of arguments passed
to each strategy given EvicPod call can encapsulate both the check
and the invocation of the pod eviction itself.
Only over utilized nodes need clasification of pods into categories.
Thus, skipping categorizing of pods which saves computation time in cases
where the number of over utilized nodes makes less than 50% of all nodes
or their fraction.
This allows end users to more easily monitor when the descheduler evicts
a pod in their environment. Prior to adding k8s event support the only
way to track evicted pods was to view the logs.
