Add New PodLifeTime Strategy

.gitignore

@@ -2,4 +2,4 @@ _output/
 _tmp/
 vendordiff.patch
 .idea/
-
+*.code-workspace

README.md

@@ -54,8 +54,8 @@ See the [user guide](docs/user-guide.md) in the `/docs` directory.
 ## Policy and Strategies
 
 Descheduler's policy is configurable and includes strategies that can be enabled or disabled.
-Six strategies `RemoveDuplicates`, `LowNodeUtilization`, `RemovePodsViolatingInterPodAntiAffinity`,
-`RemovePodsViolatingNodeAffinity`, `RemovePodsViolatingNodeTaints` and `RemovePodsHavingTooManyRestarts`
+Seven strategies `RemoveDuplicates`, `LowNodeUtilization`, `RemovePodsViolatingInterPodAntiAffinity`,
+`RemovePodsViolatingNodeAffinity`, `RemovePodsViolatingNodeTaints`, `RemovePodsHavingTooManyRestarts`, and `PodLifeTime`
 are currently implemented. As part of the policy, the parameters associated with the strategies can be configured too.
 By default, all strategies are enabled.
 
@@ -198,6 +198,21 @@ strategies:
          includingInitContainers: true
 ```
 
+### PodLifeTime
+
+This strategy evicts pods that are older than `.strategies.PodLifeTime.params.maxPodLifeTimeSeconds` The policy
+file should look like:
+
+````
+apiVersion: "descheduler/v1alpha1"
+kind: "DeschedulerPolicy"
+strategies:
+  "PodLifeTime":
+     enabled: true
+     params:
+        maxPodLifeTimeSeconds: 86400
+````
+
 ## Pod Evictions
 
 When the descheduler decides to evict pods from a node, it employs the following general mechanism:
@@ -265,7 +280,6 @@ Learn how to engage with the Kubernetes community on the [community page](http:/
 This roadmap is not in any particular order.
 
 * Consideration of pod affinity
-* Strategy to consider pod life time
 * Strategy to consider number of pending pods
 * Integration with cluster autoscaler
 * Integration with metrics providers for obtaining real load metrics

docs/user-guide.md

@@ -5,8 +5,10 @@ Starting with descheduler release v0.10.0 container images are available in thes
 * `eu.gcr.io/k8s-artifacts-prod/descheduler/descheduler`
 * `us.gcr.io/k8s-artifacts-prod/descheduler/descheduler`
 
+## Policy Configuration Examples
 The [examples](https://github.com/kubernetes-sigs/descheduler/tree/master/examples) directory has descheduler policy configuration examples.
 
+## CLI Options
 The descheduler has many CLI options that can be used to override its default behavior.
 ```
 descheduler --help
@@ -44,4 +46,45 @@ Flags:
       --vmodule moduleSpec               comma-separated list of pattern=N settings for file-filtered logging
 
 Use "descheduler [command] --help" for more information about a command.
-```
+```
+
+## Production Use Cases
+This section contains descriptions of real world production use cases.
+
+### Balance Cluster By Pod Age
+When initially migrating applications from a static virtual machine infrastructure to a cloud native k8s
+infrastructure there can be a tendency to treat application pods like static virtual machines. One approach
+to help prevent developers and operators from treating pods like virtual machines is to ensure that pods
+only run for a fixed amount
+of time.
+
+The `PodLifeTime` strategy can be used to ensure that old pods are evicted. It is recommended to create a
+[pod disruption budget](https://kubernetes.io/docs/tasks/run-application/configure-pdb/) for each
+application to ensure application availability.
+```
+descheduler -v=3 --evict-local-storage-pods --policy-config-file=pod-life-time.yml
+```
+
+This policy configuration file ensures that pods created more than 7 days ago are evicted.
+```
+---
+apiVersion: "descheduler/v1alpha1"
+kind: "DeschedulerPolicy"
+strategies:
+  "LowNodeUtilization":
+    enabled: false
+  "RemoveDuplicates":
+    enabled: false
+  "RemovePodsViolatingInterPodAntiAffinity":
+    enabled: false
+  "RemovePodsViolatingNodeAffinity":
+    enabled: false
+  "RemovePodsViolatingNodeTaints":
+    enabled: false
+  "RemovePodsHavingTooManyRestarts":
+    enabled: false
+  "PodLifeTime":
+    enabled: true
+    params:
+      maxPodLifeTimeSeconds: 604800 # pods run for a maximum of 7 days
+```

examples/pod-life-time.yml

@@ -0,0 +1,20 @@
+---
+apiVersion: "descheduler/v1alpha1"
+kind: "DeschedulerPolicy"
+strategies:
+  "LowNodeUtilization":
+    enabled: false
+  "RemoveDuplicates":
+    enabled: false
+  "RemovePodsViolatingInterPodAntiAffinity":
+    enabled: false
+  "RemovePodsViolatingNodeAffinity":
+    enabled: false
+  "RemovePodsViolatingNodeTaints":
+    enabled: false
+  "RemovePodsHavingTooManyRestarts":
+    enabled: false
+  "PodLifeTime":
+    enabled: true
+    params:
+      maxPodLifeTimeSeconds: 604800 # 7 days

pkg/api/types.go

@@ -17,7 +17,7 @@ limitations under the License.
 package api
 
 import (
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
@@ -49,6 +49,7 @@ type StrategyParameters struct {
 	NodeResourceUtilizationThresholds *NodeResourceUtilizationThresholds
 	NodeAffinityType                  []string
 	PodsHavingTooManyRestarts         *PodsHavingTooManyRestarts
+	MaxPodLifeTimeSeconds             *uint
 }
 
 type Percentage float64

pkg/api/v1alpha1/types.go

@@ -17,7 +17,7 @@ limitations under the License.
 package v1alpha1
 
 import (
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
@@ -49,6 +49,7 @@ type StrategyParameters struct {
 	NodeResourceUtilizationThresholds *NodeResourceUtilizationThresholds `json:"nodeResourceUtilizationThresholds,omitempty"`
 	NodeAffinityType                  []string                           `json:"nodeAffinityType,omitempty"`
 	PodsHavingTooManyRestarts         *PodsHavingTooManyRestarts         `json:"podsHavingTooManyRestarts,omitempty"`
+	MaxPodLifeTimeSeconds             *uint                              `json:"maxPodLifeTimeSeconds,omitempty"`
 }
 
 type Percentage float64

pkg/descheduler/descheduler.go

@@ -74,6 +74,7 @@ func RunDeschedulerStrategies(rs *options.DeschedulerServer, deschedulerPolicy *
 		"RemovePodsViolatingNodeAffinity":         strategies.RemovePodsViolatingNodeAffinity,
 		"RemovePodsViolatingNodeTaints":           strategies.RemovePodsViolatingNodeTaints,
 		"RemovePodsHavingTooManyRestarts":         strategies.RemovePodsHavingTooManyRestarts,
+		"PodLifeTime":                             strategies.PodLifeTime,
 	}
 
 	wait.Until(func() {

pkg/descheduler/strategies/pod_lifetime.go

@@ -0,0 +1,69 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package strategies
+
+import (
+	v1 "k8s.io/api/core/v1"
+	v1meta "k8s.io/apimachinery/pkg/apis/meta/v1"
+	clientset "k8s.io/client-go/kubernetes"
+	"k8s.io/klog"
+
+	"sigs.k8s.io/descheduler/pkg/api"
+	"sigs.k8s.io/descheduler/pkg/descheduler/evictions"
+	podutil "sigs.k8s.io/descheduler/pkg/descheduler/pod"
+)
+
+// PodLifeTime evicts pods on nodes that were created more than strategy.Params.MaxPodLifeTimeSeconds seconds ago.
+func PodLifeTime(client clientset.Interface, strategy api.DeschedulerStrategy, nodes []*v1.Node, evictLocalStoragePods bool, podEvictor *evictions.PodEvictor) {
+	if strategy.Params.MaxPodLifeTimeSeconds == nil {
+		klog.V(1).Infof("MaxPodLifeTimeSeconds not set")
+		return
+	}
+
+	for _, node := range nodes {
+		klog.V(1).Infof("Processing node: %#v", node.Name)
+		pods := listOldPodsOnNode(client, node, *strategy.Params.MaxPodLifeTimeSeconds, evictLocalStoragePods)
+		for _, pod := range pods {
+			success, err := podEvictor.EvictPod(pod, node)
+			if success {
+				klog.V(1).Infof("Evicted pod: %#v\n because it was created more than %v seconds ago", pod.Name, *strategy.Params.MaxPodLifeTimeSeconds)
+			}
+
+			if err != nil {
+				klog.Errorf("Error evicting pod: (%#v)", err)
+				break
+			}
+		}
+	}
+}
+
+func listOldPodsOnNode(client clientset.Interface, node *v1.Node, maxAge uint, evictLocalStoragePods bool) []*v1.Pod {
+	pods, err := podutil.ListEvictablePodsOnNode(client, node, evictLocalStoragePods)
+	if err != nil {
+		return nil
+	}
+
+	var oldPods []*v1.Pod
+	for _, pod := range pods {
+		podAgeSeconds := uint(v1meta.Now().Sub(pod.GetCreationTimestamp().Local()).Seconds())
+		if podAgeSeconds > maxAge {
+			oldPods = append(oldPods, pod)
+		}
+	}
+
+	return oldPods
+}