Use mdox to sync sample-adapter and doc code snippets

Author: olivierlemasle

Makefile

@@ -118,7 +118,7 @@ verify-deps:
 
 .PHONY: test
 test:
-	CGO_ENABLED=0 go test ./pkg/...
+	CGO_ENABLED=0 go test ./...
 
 .PHONY: test-adapter-container
 test-adapter-container: build-test-adapter

docs/getting-started.md

@@ -39,7 +39,7 @@ Put your provider in the `pkg/provider` directory in your repository.
 
 <summary>To get started, you&#39;ll need some imports:</summary>
 
-```go
+```go mdox-exec="go run ./hack/snippets -d package,import docs/sample-adapter/pkg/provider/provider.go"
 package provider
 
 import (
@@ -84,7 +84,7 @@ For this walkthrough, you can just return a few statically-named metrics,
 two that are namespaced, and one that's on namespaces themselves, and thus
 root-scoped:
 
-```go
+```go mdox-exec="go run ./hack/snippets -d func=*yourProvider.ListAllMetrics docs/sample-adapter/pkg/provider/provider.go"
 func (p *yourProvider) ListAllMetrics() []provider.CustomMetricInfo {
 	return []provider.CustomMetricInfo{
 		// these are mostly arbitrary examples
@@ -188,7 +188,7 @@ You'll need a handle to a RESTMapper (to map between resources and kinds)
 and dynamic client to fetch lists of objects in the cluster, if you don't
 already have sufficient information in your metrics pipeline:
 
-```go
+```go mdox-exec="go run ./hack/snippets -d type=yourProvider,func=NewProvider docs/sample-adapter/pkg/provider/provider.go"
 type yourProvider struct {
 	client dynamic.Interface
 	mapper apimeta.RESTMapper
@@ -214,7 +214,7 @@ backend in these methods.
 First, a couple of helpers, which support doing the fake "fetch"
 operation, and constructing a result object:
 
-```go
+```go mdox-exec="go run ./hack/snippets -d func=*yourProvider.valueFor,func=*yourProvider.metricFor docs/sample-adapter/pkg/provider/provider.go"
 // valueFor fetches a value from the fake list and increments it.
 func (p *yourProvider) valueFor(info provider.CustomMetricInfo) (int64, error) {
 	// normalize the value so that you treat plural resources and singular
@@ -225,7 +225,7 @@ func (p *yourProvider) valueFor(info provider.CustomMetricInfo) (int64, error) {
 	}
 
 	value := p.values[info]
-	value += 1
+	value++
 	p.values[info] = value
 
 	return value, nil
@@ -245,7 +245,7 @@ func (p *yourProvider) metricFor(value int64, name types.NamespacedName, info pr
 			Name: info.Metric,
 		},
 		// you'll want to use the actual timestamp in a real adapter
-		Timestamp: metav1.Time{time.Now()},
+		Timestamp: metav1.Time{Time: time.Now()},
 		Value:     *resource.NewMilliQuantity(value*100, resource.DecimalSI),
 	}, nil
 }
@@ -255,7 +255,7 @@ Then, you'll need to implement the two main methods. The first fetches
 a single metric value for one object (for example, for the `object` metric
 type in the HorizontalPodAutoscaler):
 
-```go
+```go mdox-exec="go run ./hack/snippets -d func=*yourProvider.GetMetricByName docs/sample-adapter/pkg/provider/provider.go"
 func (p *yourProvider) GetMetricByName(ctx context.Context, name types.NamespacedName, info provider.CustomMetricInfo, metricSelector labels.Selector) (*custom_metrics.MetricValue, error) {
 	value, err := p.valueFor(info)
 	if err != nil {
@@ -268,7 +268,7 @@ func (p *yourProvider) GetMetricByName(ctx context.Context, name types.Namespace
 The second fetches multiple metric values, one for each object in a set
 (for example, for the `pods` metric type in the HorizontalPodAutoscaler).
 
-```go
+```go mdox-exec="go run ./hack/snippets -d func=*yourProvider.GetMetricBySelector docs/sample-adapter/pkg/provider/provider.go"
 func (p *yourProvider) GetMetricBySelector(ctx context.Context, namespace string, selector labels.Selector, info provider.CustomMetricInfo, metricSelector labels.Selector) (*custom_metrics.MetricValueList, error) {
 	totalValue, err := p.valueFor(info)
 	if err != nil {
@@ -309,11 +309,10 @@ the metrics provided by your provider.
 
 <summary>First, you&#39;ll need a few imports:</summary>
 
-```go
+```go mdox-exec="go run ./hack/snippets -d package,import docs/sample-adapter/main.go"
 package main
 
 import (
-	"flag"
 	"os"
 
 	"k8s.io/apimachinery/pkg/util/wait"
@@ -324,7 +323,7 @@ import (
 	"sigs.k8s.io/custom-metrics-apiserver/pkg/provider"
 
 	// make this the path to the provider that you just wrote
-	yourprov "example.com/youradapter/pkg/provider"
+	yourprov "sigs.k8s.io/custom-metrics-apiserver/docs/sample-adapter/pkg/provider"
 )
 ```
 
@@ -333,7 +332,7 @@ import (
 With those out of the way, you can make use of the `basecmd.AdapterBase`
 struct to help set up the API server:
 
-```go
+```go mdox-exec="go run ./hack/snippets -d type=YourAdapter,func=main docs/sample-adapter/main.go"
 type YourAdapter struct {
 	basecmd.AdapterBase
 
@@ -348,10 +347,10 @@ func main() {
 	// initialize the flags, with one custom flag for the message
 	cmd := &YourAdapter{}
 	cmd.Flags().StringVar(&cmd.Message, "msg", "starting adapter...", "startup message")
-	// make sure you get the klog flags
-	logs.AddGoFlags(flag.CommandLine)
-	cmd.Flags().AddGoFlagSet(flag.CommandLine)
-	cmd.Flags().Parse(os.Args)
+	logs.AddFlags(cmd.Flags())
+	if err := cmd.Flags().Parse(os.Args); err != nil {
+		klog.Fatalf("unable to parse flags: %v", err)
+	}
 
 	provider := cmd.makeProviderOrDie()
 	cmd.WithCustomMetrics(provider)
@@ -372,7 +371,7 @@ you might need to pass configuration for connecting to the backing metrics
 solution, extra credentials, or advanced configuration. For the provider
 you wrote above, the setup code looks something like this:
 
-```go
+```go mdox-exec="go run ./hack/snippets -d func=*YourAdapter.makeProviderOrDie docs/sample-adapter/main.go"
 func (a *YourAdapter) makeProviderOrDie() provider.CustomMetricsProvider {
 	client, err := a.DynamicClient()
 	if err != nil {

docs/sample-adapter/main.go

@@ -0,0 +1,74 @@
+// Copyright 2022 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 main
+
+import (
+	"os"
+
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/component-base/logs"
+	"k8s.io/klog/v2"
+
+	basecmd "sigs.k8s.io/custom-metrics-apiserver/pkg/cmd"
+	"sigs.k8s.io/custom-metrics-apiserver/pkg/provider"
+
+	// make this the path to the provider that you just wrote
+	yourprov "sigs.k8s.io/custom-metrics-apiserver/docs/sample-adapter/pkg/provider"
+)
+
+type YourAdapter struct {
+	basecmd.AdapterBase
+
+	// the message printed on startup
+	Message string
+}
+
+func main() {
+	logs.InitLogs()
+	defer logs.FlushLogs()
+
+	// initialize the flags, with one custom flag for the message
+	cmd := &YourAdapter{}
+	cmd.Flags().StringVar(&cmd.Message, "msg", "starting adapter...", "startup message")
+	logs.AddFlags(cmd.Flags())
+	if err := cmd.Flags().Parse(os.Args); err != nil {
+		klog.Fatalf("unable to parse flags: %v", err)
+	}
+
+	provider := cmd.makeProviderOrDie()
+	cmd.WithCustomMetrics(provider)
+	// you could also set up external metrics support,
+	// if your provider supported it:
+	// cmd.WithExternalMetrics(provider)
+
+	klog.Infof(cmd.Message)
+	if err := cmd.Run(wait.NeverStop); err != nil {
+		klog.Fatalf("unable to run custom metrics adapter: %v", err)
+	}
+}
+
+func (a *YourAdapter) makeProviderOrDie() provider.CustomMetricsProvider {
+	client, err := a.DynamicClient()
+	if err != nil {
+		klog.Fatalf("unable to construct dynamic client: %v", err)
+	}
+
+	mapper, err := a.RESTMapper()
+	if err != nil {
+		klog.Fatalf("unable to construct discovery REST mapper: %v", err)
+	}
+
+	return yourprov.NewProvider(client, mapper)
+}

docs/sample-adapter/pkg/provider/provider.go

@@ -0,0 +1,140 @@
+// Copyright 2022 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 provider
+
+import (
+	"context"
+	"time"
+
+	apimeta "k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/api/resource"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/labels"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/client-go/dynamic"
+	"k8s.io/metrics/pkg/apis/custom_metrics"
+
+	"sigs.k8s.io/custom-metrics-apiserver/pkg/provider"
+	"sigs.k8s.io/custom-metrics-apiserver/pkg/provider/helpers"
+)
+
+type yourProvider struct {
+	client dynamic.Interface
+	mapper apimeta.RESTMapper
+
+	// just increment values when they're requested
+	values map[provider.CustomMetricInfo]int64
+}
+
+func NewProvider(client dynamic.Interface, mapper apimeta.RESTMapper) provider.CustomMetricsProvider {
+	return &yourProvider{
+		client: client,
+		mapper: mapper,
+		values: make(map[provider.CustomMetricInfo]int64),
+	}
+}
+
+// valueFor fetches a value from the fake list and increments it.
+func (p *yourProvider) valueFor(info provider.CustomMetricInfo) (int64, error) {
+	// normalize the value so that you treat plural resources and singular
+	// resources the same (e.g. pods vs pod)
+	info, _, err := info.Normalized(p.mapper)
+	if err != nil {
+		return 0, err
+	}
+
+	value := p.values[info]
+	value++
+	p.values[info] = value
+
+	return value, nil
+}
+
+// metricFor constructs a result for a single metric value.
+func (p *yourProvider) metricFor(value int64, name types.NamespacedName, info provider.CustomMetricInfo) (*custom_metrics.MetricValue, error) {
+	// construct a reference referring to the described object
+	objRef, err := helpers.ReferenceFor(p.mapper, name, info)
+	if err != nil {
+		return nil, err
+	}
+
+	return &custom_metrics.MetricValue{
+		DescribedObject: objRef,
+		Metric: custom_metrics.MetricIdentifier{
+			Name: info.Metric,
+		},
+		// you'll want to use the actual timestamp in a real adapter
+		Timestamp: metav1.Time{Time: time.Now()},
+		Value:     *resource.NewMilliQuantity(value*100, resource.DecimalSI),
+	}, nil
+}
+
+func (p *yourProvider) GetMetricByName(ctx context.Context, name types.NamespacedName, info provider.CustomMetricInfo, metricSelector labels.Selector) (*custom_metrics.MetricValue, error) {
+	value, err := p.valueFor(info)
+	if err != nil {
+		return nil, err
+	}
+	return p.metricFor(value, name, info)
+}
+
+func (p *yourProvider) GetMetricBySelector(ctx context.Context, namespace string, selector labels.Selector, info provider.CustomMetricInfo, metricSelector labels.Selector) (*custom_metrics.MetricValueList, error) {
+	totalValue, err := p.valueFor(info)
+	if err != nil {
+		return nil, err
+	}
+
+	names, err := helpers.ListObjectNames(p.mapper, p.client, namespace, selector, info)
+	if err != nil {
+		return nil, err
+	}
+
+	res := make([]custom_metrics.MetricValue, len(names))
+	for i, name := range names {
+		// in a real adapter, you might want to consider pre-computing the
+		// object reference created in metricFor, instead of recomputing it
+		// for each object.
+		value, err := p.metricFor(100*totalValue/int64(len(res)), types.NamespacedName{Namespace: namespace, Name: name}, info)
+		if err != nil {
+			return nil, err
+		}
+		res[i] = *value
+	}
+
+	return &custom_metrics.MetricValueList{
+		Items: res,
+	}, nil
+}
+
+func (p *yourProvider) ListAllMetrics() []provider.CustomMetricInfo {
+	return []provider.CustomMetricInfo{
+		// these are mostly arbitrary examples
+		{
+			GroupResource: schema.GroupResource{Group: "", Resource: "pods"},
+			Metric:        "packets-per-second",
+			Namespaced:    true,
+		},
+		{
+			GroupResource: schema.GroupResource{Group: "", Resource: "services"},
+			Metric:        "connections-per-second",
+			Namespaced:    true,
+		},
+		{
+			GroupResource: schema.GroupResource{Group: "", Resource: "namespaces"},
+			Metric:        "work-queue-length",
+			Namespaced:    false,
+		},
+	}
+}