Merge pull request #413 from damemi/podtopologyspread

Add PodTopologySpread strategy

README.md

@@ -37,6 +37,7 @@ Table of Contents
      * [RemovePodsViolatingInterPodAntiAffinity](#removepodsviolatinginterpodantiaffinity)
      * [RemovePodsViolatingNodeAffinity](#removepodsviolatingnodeaffinity)
      * [RemovePodsViolatingNodeTaints](#removepodsviolatingnodetaints)
+     * [RemovePodsViolatingTopologySpreadConstraint](#removepodsviolatingtopologyspreadconstraint)
      * [RemovePodsHavingTooManyRestarts](#removepodshavingtoomanyrestarts)
      * [PodLifeTime](#podlifetime)
   * [Filter Pods](#filter-pods)
@@ -102,17 +103,17 @@ 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.
-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.
+Eight strategies `RemoveDuplicates`, `LowNodeUtilization`, `RemovePodsViolatingInterPodAntiAffinity`,
+`RemovePodsViolatingNodeAffinity`, `RemovePodsViolatingNodeTaints`, `RemovePodsViolatingTopologySpreadConstraint`,
+`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.
 
 The policy also includes common configuration for all the strategies:
 - `nodeSelector` - limiting the nodes which are processed
 - `evictLocalStoragePods` - allowing to evict pods with local storage
 - `maxNoOfPodsToEvictPerNode` - maximum number of pods evicted from each node (summed through all strategies)
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 nodeSelector: prod=dev
@@ -144,7 +145,7 @@ has any of these `Kind`s listed as an `OwnerRef`, that pod will not be considere
 |`thresholdPriorityClassName`|string (see [priority filtering](#priority-filtering))|
 
 **Example:**
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -186,7 +187,7 @@ These thresholds, `thresholds` and `targetThresholds`, could be tuned as per you
 
 **Example:**
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -236,7 +237,7 @@ node.
 
 **Example:**
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -273,7 +274,7 @@ podA gets evicted from nodeA.
 
 **Example:**
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -301,14 +302,39 @@ and will be evicted.
 
 **Example:**
 
-````
+````yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
   "RemovePodsViolatingNodeTaints":
     enabled: true
 ````
 
+### RemovePodsViolatingTopologySpreadConstraint
+
+This strategy makes sure that pods violating [topology spread constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/)
+are evicted from nodes. Specifically, it tries to evict the minimum number of pods required to balance topology domains to within each constraint's `maxSkew`.
+This strategy requires k8s version 1.18 at a minimum.
+
+**Parameters:**
+
+|Name|Type|
+|---|---|
+|`thresholdPriority`|int (see [priority filtering](#priority-filtering))|
+|`thresholdPriorityClassName`|string (see [priority filtering](#priority-filtering))|
+|`namespaces`|(see [namespace filtering](#namespace-filtering))|
+
+**Example:**
+
+```yaml
+apiVersion: "descheduler/v1alpha1"
+kind: "DeschedulerPolicy"
+strategies:
+  "RemovePodsViolatingTopologySpreadConstraint":
+     enabled: true
+```
+
+
 ### RemovePodsHavingTooManyRestarts
 
 This strategy makes sure that pods having too many restarts are removed from nodes. For example a pod with EBS/PD that 
@@ -328,7 +354,7 @@ which determines whether init container restarts should be factored into that ca
 
 **Example:**
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -359,7 +385,7 @@ to `Running` and `Pending`.
 
 **Example:**
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -383,10 +409,11 @@ The following strategies accept a `namespaces` parameter which allows to specify
 * `RemovePodsViolatingNodeAffinity`
 * `RemovePodsViolatingInterPodAntiAffinity`
 * `RemoveDuplicates`
+* `RemovePodsViolatingTopologySpreadConstraint`
 
 For example:
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -404,7 +431,7 @@ strategies:
 In the examples `PodLifeTime` gets executed only over `namespace1` and `namespace2`.
 The similar holds for `exclude` field:
 
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -432,7 +459,7 @@ is set to the value of `system-cluster-critical` priority class.
 E.g.
 
 Setting `thresholdPriority`
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:
@@ -445,7 +472,7 @@ strategies:
 ```
 
 Setting `thresholdPriorityClassName`
-```
+```yaml
 apiVersion: "descheduler/v1alpha1"
 kind: "DeschedulerPolicy"
 strategies:

go.sum

@@ -144,6 +144,7 @@ github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7a
 github.com/gogo/protobuf v1.2.1/go.mod h1:hp+jE20tsWTFYpLwKvXlhS1hjn+gTNwPg2I6zVXpSg4=
 github.com/gogo/protobuf v1.3.1 h1:DqDEcV5aeaTmdFBePNpYsp3FlcVH/2ISVVM9Qf8PSls=
 github.com/gogo/protobuf v1.3.1/go.mod h1:SlYgWuQ5SjCEi6WLHjHCa1yvBfUnHcTbrrZtXPKa29o=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/groupcache v0.0.0-20160516000752-02826c3e7903 h1:LbsanbbD6LieFkXbj9YNNBupiGHJgFeLpO0j0Fza1h8=
 github.com/golang/groupcache v0.0.0-20160516000752-02826c3e7903/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=

kubernetes/base/rbac.yaml

@@ -10,6 +10,9 @@ rules:
 - apiGroups: [""]
   resources: ["nodes"]
   verbs: ["get", "watch", "list"]
+- apiGroups: [""]
+  resources: ["namespaces"]
+  verbs: ["get", "list"]
 - apiGroups: [""]
   resources: ["pods"]
   verbs: ["get", "watch", "list", "delete"]

pkg/descheduler/descheduler.go

@@ -70,13 +70,14 @@ func RunDeschedulerStrategies(ctx context.Context, rs *options.DeschedulerServer
 	sharedInformerFactory.WaitForCacheSync(stopChannel)
 
 	strategyFuncs := map[string]strategyFunction{
-		"RemoveDuplicates":                        strategies.RemoveDuplicatePods,
-		"LowNodeUtilization":                      strategies.LowNodeUtilization,
-		"RemovePodsViolatingInterPodAntiAffinity": strategies.RemovePodsViolatingInterPodAntiAffinity,
-		"RemovePodsViolatingNodeAffinity":         strategies.RemovePodsViolatingNodeAffinity,
-		"RemovePodsViolatingNodeTaints":           strategies.RemovePodsViolatingNodeTaints,
-		"RemovePodsHavingTooManyRestarts":         strategies.RemovePodsHavingTooManyRestarts,
-		"PodLifeTime":                             strategies.PodLifeTime,
+		"RemoveDuplicates":                            strategies.RemoveDuplicatePods,
+		"LowNodeUtilization":                          strategies.LowNodeUtilization,
+		"RemovePodsViolatingInterPodAntiAffinity":     strategies.RemovePodsViolatingInterPodAntiAffinity,
+		"RemovePodsViolatingNodeAffinity":             strategies.RemovePodsViolatingNodeAffinity,
+		"RemovePodsViolatingNodeTaints":               strategies.RemovePodsViolatingNodeTaints,
+		"RemovePodsHavingTooManyRestarts":             strategies.RemovePodsHavingTooManyRestarts,
+		"PodLifeTime":                                 strategies.PodLifeTime,
+		"RemovePodsViolatingTopologySpreadConstraint": strategies.RemovePodsViolatingTopologySpreadConstraint,
 	}
 
 	nodeSelector := rs.NodeSelector