add ignoreMinNodesCheck to allow disabling minimum node size check

Signed-off-by: Amir Alavi <amiralavi7@gmail.com>
kubernetes-sigs · Feb 11, 2024 · 27e7675 · 27e7675
1 parent 6c865fd
commit 27e7675
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Showing 12 changed files with 99 additions and 8 deletions.
diff --git a/README.md b/README.md
@@ -127,6 +127,7 @@ These are top level keys in the Descheduler Policy that you can use to configure
 | `nodeSelector` |`string`| `nil` | limiting the nodes which are processed. Only used when `nodeFit`=`true` and only by the PreEvictionFilter Extension Point |
 | `maxNoOfPodsToEvictPerNode` |`int`| `nil` | maximum number of pods evicted from each node (summed through all strategies) |
 | `maxNoOfPodsToEvictPerNamespace` |`int`| `nil` | maximum number of pods evicted from each namespace (summed through all strategies) |
+| `ignoreMinNodesCheck` |`bool`| `nil` | descheduler requires more than one node in the cluster, setting this to `true` will disable the check |
 
 ### Evictor Plugin configuration (Default Evictor)
 

diff --git a/docs/deprecated/v1alpha1.md b/docs/deprecated/v1alpha1.md
@@ -155,6 +155,7 @@ evictLocalStoragePods: true
 evictSystemCriticalPods: true
 maxNoOfPodsToEvictPerNode: 40
 ignorePvcPods: false
+ignoreMinNodesCheck: false
 strategies:
   ...
 ```

diff --git a/pkg/api/types.go b/pkg/api/types.go
@@ -38,6 +38,9 @@ type DeschedulerPolicy struct {
 
 	// MaxNoOfPodsToEvictPerNamespace restricts maximum of pods to be evicted per namespace.
 	MaxNoOfPodsToEvictPerNamespace *uint
+
+	// IgnoreMinNodesCheck allows skipping the min nodes check, if set to true.
+	IgnoreMinNodesCheck *bool
 }
 
 // Namespaces carries a list of included/excluded namespaces

diff --git a/pkg/api/v1alpha1/conversion.go b/pkg/api/v1alpha1/conversion.go
@@ -234,6 +234,7 @@ func V1alpha1ToInternal(
 	out.NodeSelector = deschedulerPolicy.NodeSelector
 	out.MaxNoOfPodsToEvictPerNamespace = deschedulerPolicy.MaxNoOfPodsToEvictPerNamespace
 	out.MaxNoOfPodsToEvictPerNode = deschedulerPolicy.MaxNoOfPodsToEvictPerNode
+	out.IgnoreMinNodesCheck = deschedulerPolicy.IgnoreMinNodesCheck
 
 	return nil
 }

diff --git a/pkg/api/v1alpha1/types.go b/pkg/api/v1alpha1/types.go
@@ -49,6 +49,9 @@ type DeschedulerPolicy struct {
 
 	// MaxNoOfPodsToEvictPerNamespace restricts maximum of pods to be evicted per namespace.
 	MaxNoOfPodsToEvictPerNamespace *uint `json:"maxNoOfPodsToEvictPerNamespace,omitempty"`
+
+	// IgnoreMinNodesCheck allows skipping the min nodes check, if set to true.
+	IgnoreMinNodesCheck *bool `json:"ignoreMinNodesCheck,omitempty"`
 }
 
 type (

diff --git a/pkg/api/v1alpha1/zz_generated.deepcopy.go b/pkg/api/v1alpha1/zz_generated.deepcopy.go
diff --git a/pkg/api/v1alpha2/types.go b/pkg/api/v1alpha2/types.go
@@ -37,6 +37,9 @@ type DeschedulerPolicy struct {
 
 	// MaxNoOfPodsToEvictPerNamespace restricts maximum of pods to be evicted per namespace.
 	MaxNoOfPodsToEvictPerNamespace *uint `json:"maxNoOfPodsToEvictPerNamespace,omitempty"`
+
+	// IgnoreMinNodesCheck allows skipping the min nodes check, if set to true.
+	IgnoreMinNodesCheck *bool `json:"ignoreMinNodesCheck,omitempty"`
 }
 
 type DeschedulerProfile struct {

diff --git a/pkg/api/v1alpha2/zz_generated.conversion.go b/pkg/api/v1alpha2/zz_generated.conversion.go
diff --git a/pkg/api/v1alpha2/zz_generated.deepcopy.go b/pkg/api/v1alpha2/zz_generated.deepcopy.go
diff --git a/pkg/api/zz_generated.deepcopy.go b/pkg/api/zz_generated.deepcopy.go
diff --git a/pkg/descheduler/descheduler.go b/pkg/descheduler/descheduler.go
@@ -25,25 +25,25 @@ import (
 
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
-	"k8s.io/apimachinery/pkg/api/meta"
-	"k8s.io/client-go/discovery"
-	"k8s.io/client-go/informers"
-	"k8s.io/client-go/tools/events"
-	componentbaseconfig "k8s.io/component-base/config"
-	"k8s.io/klog/v2"
-
 	v1 "k8s.io/api/core/v1"
 	policy "k8s.io/api/policy/v1"
+	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
 	utilversion "k8s.io/apimachinery/pkg/util/version"
 	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/informers"
 	clientset "k8s.io/client-go/kubernetes"
 	fakeclientset "k8s.io/client-go/kubernetes/fake"
 	listersv1 "k8s.io/client-go/listers/core/v1"
 	schedulingv1 "k8s.io/client-go/listers/scheduling/v1"
 	core "k8s.io/client-go/testing"
+	"k8s.io/client-go/tools/events"
+	componentbaseconfig "k8s.io/component-base/config"
+	"k8s.io/klog/v2"
+	"k8s.io/utils/ptr"
 
 	"sigs.k8s.io/descheduler/pkg/descheduler/client"
 	eutils "sigs.k8s.io/descheduler/pkg/descheduler/evictions/utils"
@@ -116,8 +116,9 @@ func (d *descheduler) runDeschedulerLoop(ctx context.Context, nodes []*v1.Node)
 		metrics.DeschedulerLoopDuration.With(map[string]string{}).Observe(time.Since(loopStartDuration).Seconds())
 	}(time.Now())
 
+	shouldCheckMinNodes := !ptr.Deref(d.deschedulerPolicy.IgnoreMinNodesCheck, false)
 	// if len is still <= 1 error out
-	if len(nodes) <= 1 {
+	if shouldCheckMinNodes && len(nodes) <= 1 {
 		klog.V(1).InfoS("The cluster size is 0 or 1 meaning eviction causes service disruption or degradation. So aborting..")
 		return fmt.Errorf("the cluster size is 0 or 1")
 	}

diff --git a/pkg/descheduler/descheduler_test.go b/pkg/descheduler/descheduler_test.go
@@ -13,8 +13,11 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	apiversion "k8s.io/apimachinery/pkg/version"
 	fakediscovery "k8s.io/client-go/discovery/fake"
+	"k8s.io/client-go/informers"
 	fakeclientset "k8s.io/client-go/kubernetes/fake"
 	core "k8s.io/client-go/testing"
+	"k8s.io/client-go/tools/events"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/descheduler/cmd/descheduler/app/options"
 	"sigs.k8s.io/descheduler/pkg/api"
 	"sigs.k8s.io/descheduler/pkg/api/v1alpha1"
@@ -248,6 +251,64 @@ func TestRootCancelWithNoInterval(t *testing.T) {
 	}
 }
 
+func TestRunDeschedulerLoop(t *testing.T) {
+	n1 := test.BuildTestNode("n1", 2000, 3000, 10, nil)
+	n2 := test.BuildTestNode("n2", 2000, 3000, 10, nil)
+
+	testCases := map[string]struct {
+		expectError       bool
+		deschedulerPolicy *api.DeschedulerPolicy
+		nodes             []*v1.Node
+	}{
+		"nodes=1, IgnoreMinNodesCheck=true, no error": {
+			expectError:       false,
+			deschedulerPolicy: &api.DeschedulerPolicy{IgnoreMinNodesCheck: ptr.To[bool](true)},
+			nodes:             []*v1.Node{n1},
+		},
+		"nodes=1, IgnoreMinNodesCheck=false, has error": {
+			expectError:       true,
+			deschedulerPolicy: &api.DeschedulerPolicy{IgnoreMinNodesCheck: ptr.To[bool](false)},
+			nodes:             []*v1.Node{n1},
+		},
+		"nodes=1, IgnoreMinNodesCheck=nil, has error": {
+			expectError:       true,
+			deschedulerPolicy: &api.DeschedulerPolicy{IgnoreMinNodesCheck: nil},
+			nodes:             []*v1.Node{n1},
+		},
+		"nodes=2, IgnoreMinNodesCheck=false, no error": {
+			expectError:       false,
+			deschedulerPolicy: &api.DeschedulerPolicy{IgnoreMinNodesCheck: ptr.To[bool](false)},
+			nodes:             []*v1.Node{n1, n2},
+		},
+		"nodes=2, IgnoreMinNodesCheck=true, no error": {
+			expectError:       false,
+			deschedulerPolicy: &api.DeschedulerPolicy{IgnoreMinNodesCheck: ptr.To[bool](true)},
+			nodes:             []*v1.Node{n1, n2},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			ctx := context.Background()
+			fakeClient := fakeclientset.NewSimpleClientset(n1, n2)
+
+			eventRecorder := &events.FakeRecorder{}
+			sharedInformerFactory := informers.NewSharedInformerFactory(fakeClient, 0)
+
+			instance, err := newDescheduler(ctx, &options.DeschedulerServer{}, tc.deschedulerPolicy, "v1", eventRecorder, sharedInformerFactory)
+			if err != nil {
+				t.Fatalf("unable to initialize descheduler")
+			}
+
+			err = instance.runDeschedulerLoop(ctx, tc.nodes)
+			hasError := err != nil
+			if tc.expectError != hasError {
+				t.Errorf("unexpected descheduler loop behavior. err %v", err)
+			}
+		})
+	}
+}
+
 func TestValidateVersionCompatibility(t *testing.T) {
 	type testCase struct {
 		name               string