Add guest config

Signed-off-by: Adrian Cole <[email protected]>

examples/nodenumber/main.go

@@ -27,14 +27,18 @@ import (
 
 	"sigs.k8s.io/kube-scheduler-wasm-extension/examples/nodenumber/plugin"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/enqueue"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/host"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/prescore"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/score"
 )
 
 // main is compiled to a WebAssembly function named "_start", called by the
 // wasm scheduler plugin during initialization.
 func main() {
-	plugin := &plugin.NodeNumber{}
+	plugin, err := plugin.New(host.Get())
+	if err != nil {
+		panic(err)
+	}
 	// Below is like `var _ api.EnqueueExtensions = plugin`, except it also
 	// wires up functions the host should provide (go:wasmimport).
 	enqueue.SetPlugin(plugin)

examples/nodenumber/plugin/plugin.go

@@ -22,14 +22,16 @@
 //   - Doesn't return an error if state has the wrong type, as it is
 //     impossible: this panics instead with the default message.
 //   - TODO: logging
-//   - TODO: config
 //
 // See https://github.com/kubernetes-sigs/kube-scheduler-simulator/blob/simulator/v0.1.0/simulator/docs/sample/nodenumber/plugin.go
 //
 // Note: This is intentionally separate from the main package, for testing.
 package plugin
 
 import (
+	"encoding/json"
+	"fmt"
+
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api/proto"
 )
@@ -50,6 +52,21 @@ type NodeNumber struct {
 	reverse bool
 }
 
+// New creates a new NodeNumber plugin for the given host or returns an error.
+func New(host api.Host) (*NodeNumber, error) {
+	var args nodeNumberArgs
+	if config := host.GetConfig(); config != nil {
+		if err := json.Unmarshal(config, &args); err != nil {
+			return nil, fmt.Errorf("decode arg into NodeNumberArgs: %w", err)
+		}
+	}
+	return &NodeNumber{reverse: args.Reverse}, nil
+}
+
+type nodeNumberArgs struct {
+	Reverse bool `json:"reverse"`
+}
+
 const (
 	// Name is the name of the plugin used in the plugin registry and configurations.
 	Name             = "NodeNumber"

guest/api/host.go

@@ -0,0 +1,12 @@
+package api
+
+// Host is the WebAssembly host side of the scheduler. Specifically, this
+// scheduler framework.Plugin written in Go, which runs the Plugin this SDK
+// compiles to Wasm.
+type Host interface {
+	// GetConfig reads any configuration set by the host.
+	//
+	// Note: This is not updated dynamically.
+	GetConfig() []byte
+	// ^-- Note: This is a []byte, not a string, for json.Unmarshaler.
+}

guest/host/host.go

@@ -0,0 +1,57 @@
+/*
+   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 host imports an api.Host from the WebAssembly host.
+package host
+
+import (
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
+	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/mem"
+)
+
+// Get can be called at any time, to use features exported by the host.
+//
+// For example:
+//
+//	func main() {
+//		config := host.Get().GetConfig()
+//		// decode yaml
+//	}
+func Get() api.Host {
+	return currentHost
+}
+
+var currentHost api.Host = &host{}
+
+type host struct {
+	config []byte
+}
+
+func (n *host) GetConfig() []byte {
+	return n.lazyConfig()
+}
+
+func (n *host) lazyConfig() []byte {
+	if config := n.config; config != nil {
+		return config
+	}
+
+	// Wrap to avoid TinyGo 0.28: cannot use an exported function as value
+	n.config = mem.GetBytes(func(ptr uint32, limit mem.BufLimit) (len uint32) {
+		return getConfig(ptr, limit)
+	})
+	return n.config
+}

guest/host/imports.go

@@ -0,0 +1,24 @@
+//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 host
+
+import "sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/mem"
+
+//go:wasmimport k8s.io/scheduler get_config
+func getConfig(ptr uint32, limit mem.BufLimit) (len uint32)

guest/host/imports_stub.go

@@ -0,0 +1,24 @@
+//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 host
+
+import "sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/mem"
+
+// getConfig is stubbed for compilation outside TinyGo.
+func getConfig(ptr uint32, limit mem.BufLimit) (len uint32) { return }

guest/internal/mem/mem.go

@@ -68,6 +68,27 @@ func Update(
 	return updater(readBuf)
 }
 
+func GetBytes(fn func(ptr uint32, limit BufLimit) (len uint32)) []byte {
+	size := fn(uint32(readBufPtr), readBufLimit)
+	if size == 0 {
+		return nil
+	}
+
+	buf := make([]byte, size)
+
+	// If the function result fit in our read buffer, copy it out.
+	if size <= readBufLimit {
+		copy(buf, readBuf[:size])
+		return buf
+	}
+
+	// If the size returned from the function was larger than our read buffer,
+	// we need to execute it again.
+	ptr := unsafe.Pointer(&buf[0])
+	_ = fn(uint32(uintptr(ptr)), size)
+	return buf
+}
+
 func GetString(fn func(ptr uint32, limit BufLimit) (len uint32)) string {
 	size := fn(uint32(readBufPtr), readBufLimit)
 	if size == 0 {

internal/e2e/scheduler/scheduler_test.go

@@ -18,6 +18,7 @@ package scheduler_test
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"testing"
 
@@ -52,7 +53,7 @@ func TestCycleStateCoherence(t *testing.T) {
 
 func TestExample_NodeNumber(t *testing.T) {
 	ctx := context.Background()
-	plugin := newPlugin(ctx, t)
+	plugin := newNodeNumberPlugin(ctx, t, false)
 	defer plugin.(io.Closer).Close()
 
 	pod := &v1.Pod{Spec: v1.PodSpec{NodeName: "happy8"}}
@@ -74,18 +75,29 @@ func TestExample_NodeNumber(t *testing.T) {
 			t.Fatalf("unexpected score: want %v, have %v", want, have)
 		}
 	})
+
+	t.Run("Reverse means score zero on match", func(t *testing.T) {
+		// This proves we can read configuration.
+		reversed := newNodeNumberPlugin(ctx, t, true)
+		defer reversed.(io.Closer).Close()
+
+		score := e2e.RunAll(ctx, t, reversed, pod, nodeInfoWithName("glad8"))
+		if want, have := int64(0), score; want != have {
+			t.Fatalf("unexpected score: want %v, have %v", want, have)
+		}
+	})
 }
 
 func BenchmarkExample_NodeNumber(b *testing.B) {
 	ctx := context.Background()
 	b.Run("New", func(b *testing.B) {
 		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
-			newPlugin(ctx, b).(io.Closer).Close()
+			newNodeNumberPlugin(ctx, b, false).(io.Closer).Close()
 		}
 	})
 
-	plugin := newPlugin(ctx, b)
+	plugin := newNodeNumberPlugin(ctx, b, false)
 	defer plugin.(io.Closer).Close()
 
 	pod := *test.PodReal // copy
@@ -102,8 +114,11 @@ func BenchmarkExample_NodeNumber(b *testing.B) {
 	})
 }
 
-func newPlugin(ctx context.Context, t e2e.Testing) framework.Plugin {
-	plugin, err := wasm.NewFromConfig(ctx, wasm.PluginConfig{GuestPath: test.PathExampleNodeNumber})
+func newNodeNumberPlugin(ctx context.Context, t e2e.Testing, reverse bool) framework.Plugin {
+	plugin, err := wasm.NewFromConfig(ctx, wasm.PluginConfig{
+		GuestPath:   test.PathExampleNodeNumber,
+		GuestConfig: fmt.Sprintf(`{"reverse": %v}`, reverse),
+	})
 	if err != nil {
 		t.Fatalf("failed to create plugin: %v", err)
 	}

scheduler/plugin/config.go

@@ -20,6 +20,9 @@ type PluginConfig struct {
 	// GuestPath is the path to the guest wasm.
 	GuestPath string `json:"guestPath"`
 
+	// GuestConfig is any configuration to give to the guest.
+	GuestConfig string `json:"guestConfig"`
+
 	// Args are the os.Args the guest will receive, exposed for tests.
 	Args []string
 }

scheduler/plugin/host.go

@@ -34,6 +34,7 @@ const (
 	k8sApiNodeName                  = "nodeName"
 	k8sApiPod                       = "pod"
 	k8sScheduler                    = "k8s.io/scheduler"
+	k8sSchedulerGetConfig           = "get_config"
 	k8sSchedulerResultClusterEvents = "result.cluster_events"
 	k8sSchedulerResultNodeNames     = "result.node_names"
 	k8sSchedulerResultStatusReason  = "result.status_reason"
@@ -56,8 +57,12 @@ func instantiateHostApi(ctx context.Context, runtime wazero.Runtime) (wazeroapi.
 		Instantiate(ctx)
 }
 
-func instantiateHostScheduler(ctx context.Context, runtime wazero.Runtime) (wazeroapi.Module, error) {
+func instantiateHostScheduler(ctx context.Context, runtime wazero.Runtime, guestConfig string) (wazeroapi.Module, error) {
+	host := &host{guestConfig: guestConfig}
 	return runtime.NewHostModuleBuilder(k8sScheduler).
+		NewFunctionBuilder().
+		WithGoModuleFunction(wazeroapi.GoModuleFunc(host.k8sSchedulerGetConfigFn), []wazeroapi.ValueType{i32, i32}, []wazeroapi.ValueType{i32}).
+		WithParameterNames("buf", "buf_limit").Export(k8sSchedulerGetConfig).
 		NewFunctionBuilder().
 		WithGoModuleFunction(wazeroapi.GoModuleFunc(k8sSchedulerResultClusterEventsFn), []wazeroapi.ValueType{i32, i32}, []wazeroapi.ValueType{}).
 		WithParameterNames("buf", "buf_len").Export(k8sSchedulerResultClusterEvents).
@@ -154,6 +159,19 @@ func k8sApiPodFn(ctx context.Context, mod wazeroapi.Module, stack []uint64) {
 	stack[0] = uint64(marshalIfUnderLimit(mod.Memory(), pod, buf, bufLimit))
 }
 
+type host struct {
+	guestConfig string
+}
+
+func (h host) k8sSchedulerGetConfigFn(_ context.Context, mod wazeroapi.Module, stack []uint64) {
+	buf := uint32(stack[0])
+	bufLimit := bufLimit(stack[1])
+
+	config := h.guestConfig
+
+	stack[0] = uint64(writeStringIfUnderLimit(mod.Memory(), config, buf, bufLimit))
+}
+
 // k8sSchedulerResultClusterEventsFn is a function used by the wasm guest to set the
 // cluster events result from guestExportEnqueue.
 func k8sSchedulerResultClusterEventsFn(ctx context.Context, mod wazeroapi.Module, stack []uint64) {

scheduler/plugin/plugin.go

@@ -56,7 +56,7 @@ func NewFromConfig(ctx context.Context, config PluginConfig) (framework.Plugin,
 		return nil, fmt.Errorf("wasm: error reading guest binary at %s: %w", config.GuestPath, err)
 	}
 
-	runtime, guestModule, err := prepareRuntime(ctx, guestBin)
+	runtime, guestModule, err := prepareRuntime(ctx, guestBin, config.GuestConfig)
 	if err != nil {
 		return nil, err
 	}

scheduler/plugin/plugin_test.go

@@ -347,6 +347,7 @@ func TestPreFilter(t *testing.T) {
 	tests := []struct {
 		name                  string
 		guestPath             string
+		guestConfig           string
 		args                  []string
 		globals               map[string]int32
 		pod                   *v1.Pod
@@ -391,6 +392,26 @@ wasm error: unreachable
 wasm stack trace:
 	panic_on_prefilter.$1() i32`,
 		},
+		{
+			name:               "panic no guestConfig",
+			guestPath:          test.PathErrorPanicOnGetConfig,
+			pod:                test.PodSmall,
+			expectedStatusCode: framework.Error,
+			expectedStatusMessage: `wasm: prefilter error: wasm error: unreachable
+wasm stack trace:
+	panic_on_get_config.$2() i32`,
+		},
+		{ // This only tests that configuration gets assigned
+			name:               "panic guestConfig",
+			guestPath:          test.PathErrorPanicOnGetConfig,
+			guestConfig:        "hello",
+			pod:                test.PodSmall,
+			expectedStatusCode: framework.Error,
+			expectedStatusMessage: `wasm: prefilter error: hello
+wasm error: unreachable
+wasm stack trace:
+	panic_on_get_config.$2() i32`,
+		},
 	}
 
 	for _, tc := range tests {
@@ -400,7 +421,7 @@ wasm stack trace:
 				guestPath = test.PathTestFilter
 			}
 
-			p, err := wasm.NewFromConfig(ctx, wasm.PluginConfig{GuestPath: guestPath, Args: tc.args})
+			p, err := wasm.NewFromConfig(ctx, wasm.PluginConfig{GuestPath: guestPath, Args: tc.args, GuestConfig: tc.guestConfig})
 			if err != nil {
 				t.Fatal(err)
 			}

scheduler/plugin/runtime.go

@@ -26,7 +26,7 @@ import (
 )
 
 // prepareRuntime compiles the guest and instantiates any host modules it needs.
-func prepareRuntime(ctx context.Context, guestBin []byte) (runtime wazero.Runtime, guest wazero.CompiledModule, err error) {
+func prepareRuntime(ctx context.Context, guestBin []byte, guestConfig string) (runtime wazero.Runtime, guest wazero.CompiledModule, err error) {
 	// Create the runtime, which when closed releases any resources associated with it.
 	runtime = wazero.NewRuntimeWithConfig(ctx, wazero.NewRuntimeConfig().
 		// Here are settings required by the wasm profiler wzprof:
@@ -63,7 +63,7 @@ func prepareRuntime(ctx context.Context, guestBin []byte) (runtime wazero.Runtim
 		}
 		fallthrough // proceed to more imports
 	case imports&importK8sScheduler != 0:
-		if _, err = instantiateHostScheduler(ctx, runtime); err != nil {
+		if _, err = instantiateHostScheduler(ctx, runtime, guestConfig); err != nil {
 			err = fmt.Errorf("wasm: error instantiating scheduler host functions: %w", err)
 			return
 		}