Based on https://github.com/kubernetes/client-go/blob/5194bac869679e2d68716e9eeddf23d3c13661e1/rest/plugin_test.go

README.md

Based on part of client-go tests, to add hooks to print out what endpoints the HTTP client is making to the Kubernets API server. This was useful to determine what the client was doing in regards to specific namespaced calls during the development of cloud-ingress-operator.

There are three pieces to add:

1. import net/http (lines 11-12)
2. Definition for the WrapTransport (occurs previous to func main(), lines 55-79)
3. WrapTransport Kubernetes client config (lines 117-120)

cmd-manager-main.go

package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"os"
	"runtime"

	// Add this
	 "net/http"

	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
	_ "k8s.io/client-go/plugin/pkg/client/auth"
	"k8s.io/client-go/rest"

	"github.com/openshift/cloud-ingress-operator/pkg/apis"
	"github.com/openshift/cloud-ingress-operator/pkg/controller"
	"github.com/openshift/cloud-ingress-operator/version"

	configv1 "github.com/openshift/api/config/v1"
	machineapi "github.com/openshift/machine-api-operator/pkg/apis/machine/v1beta1"

	"github.com/operator-framework/operator-sdk/pkg/k8sutil"
	kubemetrics "github.com/operator-framework/operator-sdk/pkg/kube-metrics"
	"github.com/operator-framework/operator-sdk/pkg/leader"
	"github.com/operator-framework/operator-sdk/pkg/log/zap"
	"github.com/operator-framework/operator-sdk/pkg/metrics"
	sdkVersion "github.com/operator-framework/operator-sdk/version"
	"github.com/spf13/pflag"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/util/intstr"
	"sigs.k8s.io/controller-runtime/pkg/client/config"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/manager"
	"sigs.k8s.io/controller-runtime/pkg/manager/signals"
)

// Change below variables to serve metrics on different host or port.
var (
	metricsHost               = "0.0.0.0"
	metricsPort         int32 = 8383
	operatorMetricsPort int32 = 8686
)
var log = logf.Log.WithName("cmd")

func printVersion() {
	log.Info(fmt.Sprintf("Operator Version: %s", version.Version))
	log.Info(fmt.Sprintf("Go Version: %s", runtime.Version()))
	log.Info(fmt.Sprintf("Go OS/Arch: %s/%s", runtime.GOOS, runtime.GOARCH))
	log.Info(fmt.Sprintf("Version of operator-sdk: %v", sdkVersion.Version))
}

// Add the following, up until func main()
type wrapTransport struct {
	rt http.RoundTripper
}

func (w *wrapTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	res, err := w.rt.RoundTrip(req)
	if err != nil {
		return nil, err
	}
	fmt.Printf("* RT Method = %s ; URI = %s\n", req.Method, req.URL)
	return res, nil
}

type plugin struct{}

func (*plugin) WrapTransport(rt http.RoundTripper) http.RoundTripper {
	return &wrapTransport{}
}

func (*plugin) Login() error { return nil }

func pluginProvider(string, map[string]string, rest.AuthProviderConfigPersister) (rest.AuthProvider, error) {
	return &plugin{}, nil
}

func main() {
	// Add the zap logger flag set to the CLI. The flag set must
	// be added before calling pflag.Parse().
	pflag.CommandLine.AddFlagSet(zap.FlagSet())

	// Add flags registered by imported packages (e.g. glog and
	// controller-runtime)
	pflag.CommandLine.AddGoFlagSet(flag.CommandLine)

	pflag.Parse()

	// Use a zap logr.Logger implementation. If none of the zap
	// flags are configured (or if the zap flag set is not being
	// used), this defaults to a production zap logger.
	//
	// The logger instantiated here can be changed to any logger
	// implementing the logr.Logger interface. This logger will
	// be propagated through the whole operator, generating
	// uniform and structured logs.
	logf.SetLogger(zap.Logger())

	printVersion()

	namespace, err := k8sutil.GetWatchNamespace()
	if err != nil {
		log.Error(err, "Failed to get watch namespace")
		os.Exit(1)
	}

	// Get a config to talk to the apiserver
	cfg, err := config.GetConfig()
	if err != nil {
		log.Error(err, "")
		os.Exit(1)
	}

	// Add this WrapTransport snippet
	cfg.WrapTransport = func(rt http.RoundTripper) http.RoundTripper {
		return &wrapTransport{rt}
	}

	ctx := context.TODO()
	// Become the leader before proceeding
	err = leader.Become(ctx, "cloud-ingress-operator-lock")
	if err != nil {
		log.Error(err, "")
		os.Exit(1)
	}

	// Create a new Cmd to provide shared dependencies and start components
	mgr, err := manager.New(cfg, manager.Options{
		Namespace:          namespace,
		MetricsBindAddress: fmt.Sprintf("%s:%d", metricsHost, metricsPort),
	})
	if err != nil {
		log.Error(err, "")
		os.Exit(1)
	}

	log.Info("Registering Components.")

	// Setup Scheme for all resources
	if err := apis.AddToScheme(mgr.GetScheme()); err != nil {
		log.Error(err, "")
		os.Exit(1)
	}

	if err := machineapi.AddToScheme(mgr.GetScheme()); err != nil {
		log.Error(err, "")
		os.Exit(1)
	}
	if err := configv1.AddToScheme(mgr.GetScheme()); err != nil {
		log.Error(err, "")
		os.Exit(1)
	}

	// Setup all Controllers
	if err := controller.AddToManager(mgr); err != nil {
		log.Error(err, "")
		os.Exit(1)
	}

	// Add the Metrics Service
	addMetrics(ctx, cfg, namespace)

	log.Info("Starting the Cmd.")

	// Start the Cmd
	if err := mgr.Start(signals.SetupSignalHandler()); err != nil {
		log.Error(err, "Manager exited non-zero")
		os.Exit(1)
	}
}

// addMetrics will create the Services and Service Monitors to allow the operator export the metrics by using
// the Prometheus operator
func addMetrics(ctx context.Context, cfg *rest.Config, namespace string) {
	if err := serveCRMetrics(cfg); err != nil {
		if errors.Is(err, k8sutil.ErrRunLocal) {
			log.Info("Skipping CR metrics server creation; not running in a cluster.")
			return
		}
		log.Info("Could not generate and serve custom resource metrics", "error", err.Error())
	}

	// Add to the below struct any other metrics ports you want to expose.
	servicePorts := []v1.ServicePort{
		{Port: metricsPort, Name: metrics.OperatorPortName, Protocol: v1.ProtocolTCP, TargetPort: intstr.IntOrString{Type: intstr.Int, IntVal: metricsPort}},
		{Port: operatorMetricsPort, Name: metrics.CRPortName, Protocol: v1.ProtocolTCP, TargetPort: intstr.IntOrString{Type: intstr.Int, IntVal: operatorMetricsPort}},
	}

	// Create Service object to expose the metrics port(s).
	service, err := metrics.CreateMetricsService(ctx, cfg, servicePorts)
	if err != nil {
		log.Info("Could not create metrics Service", "error", err.Error())
	}

	// CreateServiceMonitors will automatically create the prometheus-operator ServiceMonitor resources
	// necessary to configure Prometheus to scrape metrics from this operator.
	services := []*v1.Service{service}
	_, err = metrics.CreateServiceMonitors(cfg, namespace, services)
	if err != nil {
		log.Info("Could not create ServiceMonitor object", "error", err.Error())
		// If this operator is deployed to a cluster without the prometheus-operator running, it will return
		// ErrServiceMonitorNotPresent, which can be used to safely skip ServiceMonitor creation.
		if err == metrics.ErrServiceMonitorNotPresent {
			log.Info("Install prometheus-operator in your cluster to create ServiceMonitor objects", "error", err.Error())
		}
	}
}

// serveCRMetrics gets the Operator/CustomResource GVKs and generates metrics based on those types.
// It serves those metrics on "http://metricsHost:operatorMetricsPort".
func serveCRMetrics(cfg *rest.Config) error {
	// Below function returns filtered operator/CustomResource specific GVKs.
	// For more control override the below GVK list with your own custom logic.
	filteredGVK, err := k8sutil.GetGVKsFromAddToScheme(apis.AddToScheme)
	if err != nil {
		return err
	}
	// Get the namespace the operator is currently deployed in.
	operatorNs, err := k8sutil.GetOperatorNamespace()
	if err != nil {
		return err
	}
	// To generate metrics in other namespaces, add the values below.
	ns := []string{operatorNs}
	// Generate and serve custom resource specific metrics.
	err = kubemetrics.GenerateAndServeCRMetrics(cfg, ns, filteredGVK, metricsHost, operatorMetricsPort)
	if err != nil {
		return err
	}
	return nil
}