In some cases it might be usefull to limit how many evictions per a
domain can be performed. To avoid burning the whole per descheduling
cycle budget. Limiting the number of evictions per node is a
prerequisite for evicting pods whose usage can't be easily subtracted
from overall node resource usage to predict the final usage. E.g. when a
pod is evicted due to high PSI pressure which takes into account many
factors which can be fully captured by the current predictive resource
model.
This commit adds a sample plugin implementation as follow:
This directory provides an example plugin for the Kubernetes Descheduler,
demonstrating how to evict pods based on custom criteria. The plugin targets
pods based on:
* **Name Regex:** Pods matching a specified regular expression.
* **Age:** Pods older than a defined duration.
* **Namespace:** Pods within or outside a given list of namespaces (inclusion
or exclusion).
To incorporate this plugin into your Descheduler build, you must register it
within the Descheduler's plugin registry. Follow these steps:
1. **Register the Plugin:**
* Modify the `pkg/descheduler/setupplugins.go` file.
* Add the following registration line to the end of the
`RegisterDefaultPlugins()` function:
```go
pluginregistry.Register(
example.PluginName,
example.New,
&example.Example{},
&example.ExampleArgs{},
example.ValidateExampleArgs,
example.SetDefaults_Example,
registry,
)
```
2. **Generate Code:**
* If you modify the plugin's code, execute `make gen` before rebuilding the
Descheduler. This ensures generated code is up-to-date.
3. **Rebuild the Descheduler:**
* Build the descheduler with your changes.
Configure the plugin's behavior using the Descheduler's policy configuration.
Here's an example:
```yaml
apiVersion: descheduler/v1alpha2
kind: DeschedulerPolicy
profiles:
- name: LifecycleAndUtilization
plugins:
deschedule:
enabled:
- Example
pluginConfig:
- name: Example
args:
regex: ^descheduler-test.*$
maxAge: 3m
namespaces:
include:
- default
```
- `regex: ^descheduler-test.*$`: Evicts pods whose names match the regular
expression `^descheduler-test.*$`.
- `maxAge: 3m`: Evicts pods older than 3 minutes.
- `namespaces.include: - default`: Evicts pods within the default namespace.
This configuration will cause the plugin to evict pods that meet all three
criteria: matching the `regex`, exceeding the `maxAge`, and residing in the
specified namespace.
* add ignoreNonPDBPods option
* take2
* add test
* poddisruptionbudgets are now used by defaultevictor plugin
* add poddisruptionbudgets to rbac
* review comments
* don't use GetPodPodDisruptionBudgets
* review comment, don't hide error
* skip eviction when pod creation time is below minPodAge threshold setting
In the default initialization phase of the descheduler, add a new
constraint to not evict pods that creation time is below minPodAge
threshold.
Added value:
- Avoid crazy pod movement when the autoscaler scales up and down.
- Avoid evicting pods when they are warming up.
- Decreases the overall cost of eviction as no pod will be evicted
before doing significant amount of work.
- Guard against scheduling. Descheduling loops in situations where
the descheduler has a different node fit logic from scheduler,
like not considering topology spread constraints.
* Use *time.Duration instead of uint for MinPodAge type
* Remove '(in minutes)' from default evictor configuration table
* make fmt
* Add explicit name for Duration field
* Use Duration.String()
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.
