main.go

/*
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 main

import (
	"errors"
	"flag"
	"fmt"
	"net/http"
	"os"
	"time"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/component-base/logs"
	logsapi "k8s.io/component-base/logs/api/v1"
	clientset "sigs.k8s.io/node-ipam-controller/pkg/client/clientset/versioned"
	informers "sigs.k8s.io/node-ipam-controller/pkg/client/informers/externalversions"
	"sigs.k8s.io/node-ipam-controller/pkg/controller/ipam"
	"sigs.k8s.io/node-ipam-controller/pkg/signals"

	kubeinformers "k8s.io/client-go/informers"
	"k8s.io/client-go/kubernetes"

	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
	// to ensure that exec-entrypoint and run can make use of them.
	_ "k8s.io/client-go/plugin/pkg/client/auth"
	"k8s.io/client-go/tools/clientcmd"
	_ "k8s.io/component-base/logs/json/register"
	"k8s.io/klog/v2"
)

func main() {
	var (
		apiServerURL    string
		kubeconfig      string
		healthProbeAddr string
	)

	flag.StringVar(&kubeconfig, "kubeconfig", "", "Path to a kubeconfig. Only required if out-of-cluster.")
	flag.StringVar(&apiServerURL, "apiserver", "", "The address of the Kubernetes API server. Overrides any value in kubeconfig. Only required if out-of-cluster.")
	flag.StringVar(&healthProbeAddr, "health-probe-address", ":8081", "Specifies the TCP address for the health server to listen on.")

	c := logsapi.NewLoggingConfiguration()
	logsapi.AddGoFlags(c, flag.CommandLine)
	flag.Parse()
	logs.InitLogs()
	if err := logsapi.ValidateAndApply(c, nil); err != nil {
		fmt.Fprintf(os.Stderr, "%v\n", err)
		os.Exit(1)
	}
	ctx := signals.SetupSignalHandler()
	logger := klog.FromContext(ctx)

	cfg, err := clientcmd.BuildConfigFromFlags(apiServerURL, kubeconfig)
	if err != nil {
		logger.Error(err, "failed to build kubeconfig")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}

	kubeClient, err := kubernetes.NewForConfig(cfg)
	if err != nil {
		logger.Error(err, "failed to build kubernetes clientset")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}

	cidrClient, err := clientset.NewForConfig(cfg)
	if err != nil {
		logger.Error(err, "failed to build kubernetes clientset")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}

	const defaultResync = 30 * time.Second
	kubeInformerFactory := kubeinformers.NewSharedInformerFactory(kubeClient, defaultResync)
	sharedInformerFactory := informers.NewSharedInformerFactory(cidrClient, defaultResync)

	nodes, err := kubeClient.CoreV1().Nodes().List(ctx, metav1.ListOptions{})
	if err != nil {
		logger.Error(err, "failed to list existing nodes")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}

	nodeIpamController, err := ipam.NewMultiCIDRRangeAllocator(
		ctx,
		kubeClient,
		cidrClient.NetworkingV1().ClusterCIDRs(),
		kubeInformerFactory.Core().V1().Nodes(),
		sharedInformerFactory.Networking().V1().ClusterCIDRs(),
		ipam.CIDRAllocatorParams{},
		nodes,
		nil,
	)
	if err != nil {
		logger.Error(err, "failed to create Node IPAM controller")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}

	kubeInformerFactory.Start(ctx.Done())
	sharedInformerFactory.Start(ctx.Done())

	server := startHealthProbeServer(healthProbeAddr, logger)
	nodeIpamController.Run(ctx)
	if err := server.Shutdown(ctx); err != nil {
		logger.Error(err, "failed to shut down health server")
	}
}

// startHealthProbeServer starts a web server that has two endpoints `/readyz` and `/healthz` and always responds
// 200 OK.
func startHealthProbeServer(addr string, logger klog.Logger) *http.Server {
	const defaultTimeout = 30 * time.Second
	mux := http.NewServeMux()
	server := &http.Server{
		Addr:         addr,
		Handler:      mux,
		ReadTimeout:  defaultTimeout,
		WriteTimeout: defaultTimeout,
		IdleTimeout:  defaultTimeout,
	}

	mux.Handle("/readyz", makeHealthHandler())
	mux.Handle("/healthz", makeHealthHandler())

	go func() {
		err := server.ListenAndServe()
		if err != nil && !errors.Is(err, http.ErrServerClosed) {
			logger.Error(err, "an error occurred after stopping the health server")
		}
	}()

	return server
}

// makeHealthHandler returns 200/OK when healthy.
func makeHealthHandler() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		defer r.Body.Close()

		w.WriteHeader(http.StatusOK)
	}
}