support postfilter

guest/api/types.go

@@ -67,6 +67,22 @@ type FilterPlugin interface {
 	Filter(state CycleState, pod proto.Pod, nodeInfo NodeInfo) *Status
 }
 
+// PostFilterPlugin is a WebAssembly implementation of framework.PostFilterPlugin.
+type PostFilterPlugin interface {
+	Plugin
+
+	PostFilter(state CycleState, pod proto.Pod, filteredNodeStatusMap NodeToStatusMap) (nominatedNodeName string, nominatingMode NominatingMode, status *Status)
+}
+
+// NominatingMode is the Mode which is returned from PostFilter.
+type NominatingMode int32
+
+// These are predefined modes
+const (
+	ModeNoop NominatingMode = iota
+	ModeOverride
+)
+
 // EnqueueExtensions is a WebAssembly implementation of framework.EnqueueExtensions.
 type EnqueueExtensions interface {
 	EventsToRegister() []ClusterEvent
@@ -97,3 +113,8 @@ type NodeInfo interface {
 
 	Node() proto.Node
 }
+
+// PostFilterPlugin use nodeToStatusMap
+type NodeToStatusMap interface {
+	Map() map[string]StatusCode
+}

guest/internal/imports/host.go

@@ -17,6 +17,7 @@
 package imports
 
 import (
+	"encoding/json"
 	"runtime"
 
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
@@ -66,3 +67,17 @@ func Pod(updater func([]byte) error) error {
 		return k8sApiPod(ptr, limit)
 	}, updater)
 }
+
+func NodeToStatusMap() map[string]api.StatusCode {
+	// Wrap to avoid TinyGo 0.28: cannot use an exported function as value
+	jsonStr := mem.GetString(func(ptr uint32, limit mem.BufLimit) (len uint32) {
+		return k8sSchedulerNodeToStatusMap(ptr, limit)
+	})
+	byte := []byte(jsonStr)
+	var nodeToMap map[string]api.StatusCode
+	err := json.Unmarshal(byte, &nodeToMap)
+	if err != nil {
+		panic(err)
+	}
+	return nodeToMap
+}

guest/internal/imports/imports.go

@@ -29,5 +29,8 @@ func k8sApiNodeName(ptr uint32, limit mem.BufLimit) (len uint32)
 //go:wasmimport k8s.io/api pod
 func k8sApiPod(ptr uint32, limit mem.BufLimit) (len uint32)
 
+//go:wasmimport k8s.io/scheduler nodeToStatusMap
+func k8sSchedulerNodeToStatusMap(ptr uint32, limit mem.BufLimit) (len uint32)
+
 //go:wasmimport k8s.io/scheduler result.status_reason
 func k8sSchedulerResultStatusReason(ptr, size uint32)

guest/internal/imports/imports_stub.go

@@ -29,5 +29,8 @@ func k8sApiNodeName(uint32, mem.BufLimit) (len uint32) { return }
 // k8sApiPod is stubbed for compilation outside TinyGo.
 func k8sApiPod(uint32, mem.BufLimit) (len uint32) { return }
 
+// k8sSchedulerNodeToStatusMap is stubbed for compilation outside TinyGo.
+func k8sSchedulerNodeToStatusMap(uint32, mem.BufLimit) (len uint32) { return }
+
 // k8sSchedulerResultStatusReason is stubbed for compilation outside TinyGo.
 func k8sSchedulerResultStatusReason(uint32, uint32) {}

guest/plugin/plugin.go

@@ -21,6 +21,7 @@ import (
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/enqueue"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/filter"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/prefilter"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/postfilter"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/prescore"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/score"
 )
@@ -51,6 +52,9 @@ func Set(plugin api.Plugin) {
 	if plugin, ok := plugin.(api.FilterPlugin); ok {
 		filter.SetPlugin(plugin)
 	}
+	if plugin, ok := plugin.(api.PostFilterPlugin); ok {
+		postfilter.SetPlugin(plugin)
+	}
 	if plugin, ok := plugin.(api.PreScorePlugin); ok {
 		prescore.SetPlugin(plugin)
 	}

guest/postfilter/imports.go

@@ -0,0 +1,22 @@
+//go:build tinygo.wasm
+
+/*
+   Copyright 2023 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 postfilter
+
+//go:wasmimport k8s.io/scheduler result.nominated_node_name
+func setNominatedNodeNameResult(ptr, size uint32)

guest/postfilter/imports_stub.go

@@ -0,0 +1,22 @@
+//go:build !tinygo.wasm
+
+/*
+   Copyright 2023 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 postfilter
+
+// setNominatedNodeNameResult is stubbed for compilation outside TinyGo.
+func setNominatedNodeNameResult(uint32, uint32) {}

guest/postfilter/postfilter.go

@@ -0,0 +1,100 @@
+/*
+   Copyright 2023 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 postfilter exports an api.PostFilterPlugin to the host.
+package postfilter
+
+import (
+	"runtime"
+
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/cyclestate"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/imports"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/mem"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/plugin"
+)
+
+// postfilter is the current plugin assigned with SetPlugin.
+var postfilter api.PostFilterPlugin
+
+// SetPlugin should be called in `main` to assign an api.PostFilterPlugin
+// instance.
+//
+// For example:
+//
+//	func main() {
+//		plugin := filterPlugin{}
+//		postfilter.SetPlugin(plugin)
+//		filter.SetPlugin(plugin)
+//	}
+//
+//	type filterPlugin struct{}
+//
+//	func (filterPlugin) PostFilter(state api.CycleState, pod proto.Pod, filteredNodeStatusMap internalpostfilter.NodeToStatusMap) (int32, status *api.Status) {
+//		// Write state you need on Filter
+//	}
+//
+//	func (filterPlugin) Filter(state api.CycleState, pod api.Pod, nodeInfo api.NodeInfo) (status *api.Status) {
+//		var Filter int32
+//		// Derive Filter for the node name using state set on PreFilter!
+//		return Filter, nil
+//	}
+func SetPlugin(postfilterPlugin api.PostFilterPlugin) {
+	if postfilterPlugin == nil {
+		panic("nil postfilterPlugin")
+	}
+	postfilter = postfilterPlugin
+	plugin.MustSet(postfilterPlugin)
+}
+
+// prevent unused lint errors (lint is run with normal go).
+var _ func() uint64 = _postfilter
+
+// _postfilter is only exported to the host.
+//
+//export postfilter
+func _postfilter() uint64 { //nolint
+
+	if postfilter == nil { // Then, the user didn't define one.
+		// Unlike most plugins we always export postfilter so that we can reset
+		// the cycle state: return success to avoid no-op overhead.
+		return 0
+	}
+
+	// The parameters passed are lazy with regard to host functions. This means
+	// a no-op plugin should not have any unmarshal penalty.
+	nominatedNodeName, nominatingMode, status := postfilter.PostFilter(cyclestate.Values, cyclestate.Pod, &nodeToStatusMap{})
+	ptr, size := mem.StringToPtr(nominatedNodeName)
+	setNominatedNodeNameResult(ptr, size)
+	runtime.KeepAlive(nominatedNodeName) // until ptr is no longer needed.
+
+	return (uint64(nominatingMode) << uint64(32)) | uint64(imports.StatusToCode(status))
+}
+
+type nodeToStatusMap struct {
+	statusMap map[string]api.StatusCode
+}
+
+func (n *nodeToStatusMap) Map() map[string]api.StatusCode {
+	return n.lazyNodeToStatusMap()
+}
+
+// lazyNodeToStatusMap returns NodeToStatusMap from imports.NodeToStatusMap.
+func (n *nodeToStatusMap) lazyNodeToStatusMap() map[string]api.StatusCode {
+	nodeMap := imports.NodeToStatusMap()
+	n.statusMap = nodeMap
+	return n.statusMap
+}

guest/prefilter/prefilter.go

@@ -35,7 +35,7 @@ import (
 //
 //	type filterPlugin struct{}
 //
-//	func (filterPlugin) PreFilter(state api.CycleState, pod proto.Pod, nodeList proto.NodeList) {
+//	func (filterPlugin) PreFilter(state api.CycleState, pod proto.Pod) (nodeNames []string, status *Status) {
 //		// Write state you need on Filter
 //	}
 //

guest/testdata/cyclestate/main.go

@@ -26,6 +26,7 @@ import (
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api/proto"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/enqueue"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/filter"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/postfilter"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/prefilter"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/prescore"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/score"
@@ -56,6 +57,7 @@ func main() {
 	enqueue.SetPlugin(plugin)
 	prefilter.SetPlugin(plugin)
 	filter.SetPlugin(plugin)
+	postfilter.SetPlugin(plugin)
 	prescore.SetPlugin(plugin)
 	score.SetPlugin(plugin)
 }
@@ -82,11 +84,11 @@ type preFilterStateVal map[string]any
 type preScoreStateVal map[string]any
 
 func (statePlugin) PreFilter(state api.CycleState, pod proto.Pod) (nodeNames []string, status *api.Status) {
-	if nextPodSpec := pod.Spec(); unsafe.Pointer(nextPodSpec) == unsafe.Pointer(podSpec) {
+	nextPodSpec := pod.Spec()
+	if unsafe.Pointer(nextPodSpec) == unsafe.Pointer(podSpec) {
 		panic("didn't reset pod on pre-filter")
-	} else {
-		podSpec = nextPodSpec
 	}
+	podSpec = nextPodSpec
 	mustNotScoreState(state)
 	if _, ok := state.Read(preFilterStateKey); ok {
 		panic("didn't reset filter state on pre-filter")
@@ -109,10 +111,23 @@ func (statePlugin) Filter(state api.CycleState, pod proto.Pod, _ api.NodeInfo) (
 	return
 }
 
-func (statePlugin) PreScore(state api.CycleState, pod proto.Pod, _ proto.NodeList) *api.Status {
+func (statePlugin) PostFilter(state api.CycleState, pod proto.Pod, _ api.NodeToStatusMap) (nominatedNodeName string, nominatingMode api.NominatingMode, status *api.Status) {
 	if unsafe.Pointer(pod.Spec()) != unsafe.Pointer(podSpec) {
 		panic("didn't cache pod from filter")
 	}
+	mustNotScoreState(state)
+	if val, ok := state.Read(preFilterStateKey); !ok {
+		panic("didn't propagate state from pre-filter")
+	} else if _, ok = val.(preFilterStateVal)["filter"]; !ok {
+		panic("filter value lost propagating from filter")
+	}
+	return
+}
+
+func (statePlugin) PreScore(state api.CycleState, pod proto.Pod, _ proto.NodeList) *api.Status {
+	if unsafe.Pointer(pod.Spec()) != unsafe.Pointer(podSpec) {
+		panic("didn't cache pod from pre-filter")
+	}
 	mustFilterState(state)
 	if _, ok := state.Read(preScoreStateKey); ok {
 		panic("didn't reset score state on pre-score")

guest/testdata/filter/main.go

@@ -22,12 +22,14 @@ import (
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api/proto"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/filter"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/postfilter"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/prefilter"
 )
 
 type extensionPoints interface {
 	api.PreFilterPlugin
 	api.FilterPlugin
+	api.PostFilterPlugin
 }
 
 func main() {
@@ -40,10 +42,13 @@ func main() {
 			plugin = filterPlugin{}
 		case "preFilter":
 			plugin = preFilterPlugin{}
+		case "postFilter":
+			plugin = postFilterPlugin{}
 		}
 	}
 	prefilter.SetPlugin(plugin)
 	filter.SetPlugin(plugin)
+	postfilter.SetPlugin(plugin)
 }
 
 // noopPlugin doesn't do anything, except evaluate each parameter.
@@ -62,6 +67,13 @@ func (noopPlugin) Filter(state api.CycleState, pod proto.Pod, nodeInfo api.NodeI
 	return
 }
 
+func (noopPlugin) PostFilter(state api.CycleState, pod proto.Pod, nodeMap api.NodeToStatusMap) (nominatedNodeName string, nominatingMode api.NominatingMode, status *api.Status) {
+	_, _ = state.Read("ok")
+	_ = pod.Spec()
+	_ = nodeMap.Map()
+	return
+}
+
 // preFilterPlugin schedules a node if its name equals its pod spec.
 type preFilterPlugin struct{ noopPlugin }
 
@@ -96,3 +108,28 @@ func (filterPlugin) Filter(_ api.CycleState, pod proto.Pod, nodeInfo api.NodeInf
 		Reason: podSpecNodeName + " != " + nodeName,
 	}
 }
+
+type postFilterPlugin struct{ noopPlugin }
+
+func (postFilterPlugin) PostFilter(_ api.CycleState, pod proto.Pod, nodeMap api.NodeToStatusMap) (string, api.NominatingMode, *api.Status) {
+	// First, check if the pod spec node name is empty. If so, pass!
+	podSpecNodeName := pod.Spec().GetNodeName()
+	if len(podSpecNodeName) == 0 {
+		return "", 0, nil
+	}
+	m := nodeMap.Map()
+	if m == nil {
+		return "", 0, nil
+	}
+	// If nominatedNodeName is schedulable, pass!
+	if val, ok := m[podSpecNodeName]; ok {
+		if val == 0 {
+			return podSpecNodeName, api.ModeOverride, nil
+		}
+	}
+	// Otherwise, this is unschedulableAndUnresolvable, so note the reason.
+	return podSpecNodeName, api.ModeNoop, &api.Status{
+		Code:   api.StatusCodeUnschedulableAndUnresolvable,
+		Reason: podSpecNodeName + " is unschedulable",
+	}
+}

internal/e2e/e2e.go

@@ -23,6 +23,11 @@ func RunAll(ctx context.Context, t Testing, plugin framework.Plugin, pod *v1.Pod
 		RequireSuccess(t, s)
 	}
 
+	if postfilterP, ok := plugin.(framework.PostFilterPlugin); ok {
+		_, s = postfilterP.PostFilter(ctx, nil, pod, nil)
+		RequireSuccess(t, s)
+	}
+
 	if prescoreP, ok := plugin.(framework.PreScorePlugin); ok {
 		s = prescoreP.PreScore(ctx, nil, pod, []*v1.Node{ni.Node()})
 		RequireSuccess(t, s)

internal/e2e/go.mod

@@ -165,7 +165,7 @@ require (
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto v0.0.0-20220502173005-c8bf987b8c21 // indirect
 	google.golang.org/grpc v1.51.0 // indirect
-	google.golang.org/protobuf v1.30.0 // indirect
+	google.golang.org/protobuf v1.31.0 // indirect
 	gopkg.in/gcfg.v1 v1.2.0 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect
 	gopkg.in/natefinch/lumberjack.v2 v2.0.0 // indirect