Added auto detection for kubelet client config

Makefile

@@ -9,7 +9,7 @@ GOPATH := $(shell go env GOPATH)
 GORELEASER_VERSION := v0.129.0
 GORELEASER_SHA256 := e9e61de6565ad4acbe33a944abbeaf0d75582c10b89b793c99acd41a0846c166
 GORELEASER_BIN ?= bin/goreleaser
-GOLANGCILINT_VERSION = v1.24.0
+GOLANGCILINT_VERSION = v1.27.0
 GOLANGCI_LINT_BIN = bin/golangci-lint
 
 all: build

cmd/discovery/main.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"time"
 
 	cfg "github.com/newrelic/nri-discovery-kubernetes/internal/config"
 	"github.com/newrelic/nri-discovery-kubernetes/internal/discovery"
@@ -20,7 +21,8 @@ func main() {
 
 	config := cfg.NewConfig(Version)
 
-	kubelet, err := kubernetes.NewKubelet(config.Port, config.TLS)
+	timeout := time.Duration(config.Timeout) * time.Millisecond
+	kubelet, err := kubernetes.NewKubelet(config.Host, config.Port, config.TLS, config.IsAutoConfig(), timeout)
 	if err != nil {
 		log.Printf("failed to get Kubernetes configuration: %s", err)
 		os.Exit(1)

go.mod

@@ -3,19 +3,40 @@ module github.com/newrelic/nri-discovery-kubernetes
 go 1.13
 
 require (
+	cloud.google.com/go v0.38.0 // indirect
+	github.com/Azure/go-autorest/autorest v0.9.0 // indirect
+	github.com/evanphx/json-patch v4.2.0+incompatible // indirect
 	github.com/gogo/protobuf v1.3.1 // indirect
+	github.com/golang/protobuf v1.3.2 // indirect
+	github.com/google/go-cmp v0.3.0 // indirect
+	github.com/google/uuid v1.1.1 // indirect
+	github.com/gophercloud/gophercloud v0.1.0 // indirect
+	github.com/gregjones/httpcache v0.0.0-20170728041850-787624de3eb7 // indirect
+	github.com/hashicorp/golang-lru v0.5.1 // indirect
 	github.com/imdario/mergo v0.3.8 // indirect
+	github.com/json-iterator/go v1.1.8 // indirect
+	github.com/modern-go/reflect2 v1.0.1 // indirect
+	github.com/mxk/go-flowrate v0.0.0-20140419014527-cca7078d478f // indirect
+	github.com/newrelic/nri-kubernetes v1.26.5
+	github.com/onsi/ginkgo v1.10.1 // indirect
+	github.com/onsi/gomega v1.7.0 // indirect
+	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
+	github.com/sirupsen/logrus v1.2.0
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.6.2
 	github.com/stretchr/testify v1.3.0
 	golang.org/x/crypto v0.0.0-20191112222119-e1110fd1c708 // indirect
 	golang.org/x/net v0.0.0-20191112182307-2180aed22343 // indirect
+	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45 // indirect
 	golang.org/x/sys v0.0.0-20191113165036-4c7a9d0fe056 // indirect
 	golang.org/x/time v0.0.0-20191024005414-555d28b269f0 // indirect
 	google.golang.org/appengine v1.6.5 // indirect
+	gopkg.in/inf.v0 v0.9.1 // indirect
 	gopkg.in/yaml.v2 v2.2.5 // indirect
-	k8s.io/api v0.0.0-20191115095533-47f6de673b26
-	k8s.io/apimachinery v0.0.0-20191115015347-3c7067801da2
-	k8s.io/client-go v0.0.0-20191114101535-6c5935290e33
+	k8s.io/api v0.0.0-20180521142803-feb48db456a5
+	k8s.io/apimachinery v0.0.0-20180515182440-31dade610c05
+	k8s.io/client-go v7.0.0+incompatible
+	k8s.io/klog v1.0.0 // indirect
+	k8s.io/kube-openapi v0.0.0-20191107075043-30be4d16710a // indirect
 	k8s.io/utils v0.0.0-20191114200735-6ca3b61696b6 // indirect
 )

internal/config/config.go

@@ -10,22 +10,31 @@ import (
 const (
 	namespaces = "namespaces"
 	port       = "port"
+	Host       = "host"
 	insecure   = "insecure"
+	timeout    = "timeout"
 	tls        = "tls"
 	envPrefix  = "NRIA"
+
+	DefaultHost = "localhost"
+	DefaultPort = 10255
 )
 
 var _ = flag.String(namespaces, "", "(optional, default '') Comma separated list of namespaces to discover pods on")
 var _ = flag.Bool(insecure, false, `(optional, default false, deprecated) Use insecure (non-ssl) connection.
 For backwards compatibility this flag takes precedence over 'tls')`)
+var _ = flag.Int(timeout, 5000, "(optional, default 5000) timeout in ms")
 var _ = flag.Bool(tls, false, "(optional, default false) Use secure (tls) connection")
-var _ = flag.Int(port, 10255, "(optional, default 10255) Port used to connect to the kubelet")
+var _ = flag.Int(port, DefaultPort, "(optional, default 10255) Port used to connect to the kubelet")
+var _ = flag.String(Host, DefaultHost, "(optional, default "+DefaultHost+") Host used to connect to the kubelet")
 
 // Config defined the currently accepted configuration parameters of the Discoverer
 type Config struct {
 	Namespaces []string
 	Port       int
+	Host       string
 	TLS        bool
+	Timeout    int
 }
 
 func splitStrings(str string) []string {
@@ -35,14 +44,32 @@ func splitStrings(str string) []string {
 	return []string{}
 }
 
+// IsFlagPassed checks if a particular command line argument was provided or not.
+func IsFlagPassed(name string) bool {
+	found := false
+	flag.Visit(func(f *flag.Flag) {
+		if f.Name == name {
+			found = true
+		}
+	})
+	return found
+}
+
+// IsAutoConfig returns true if no config parameter was provided as cmd line arg.
+func (c *Config) IsAutoConfig() bool {
+	return !IsFlagPassed(Host) && !IsFlagPassed(port) && !IsFlagPassed(tls)
+}
+
 func NewConfig(version string) Config {
 	flag.Parse()
 
 	v := viper.New()
 	_ = v.BindPFlag(namespaces, flag.Lookup(namespaces))
 	_ = v.BindPFlag(port, flag.Lookup(port))
+	_ = v.BindPFlag(Host, flag.Lookup(Host))
 	_ = v.BindPFlag(tls, flag.Lookup(tls))
 	_ = v.BindPFlag(insecure, flag.Lookup(insecure))
+	_ = v.BindPFlag(timeout, flag.Lookup(timeout))
 
 	v.SetEnvPrefix(envPrefix)
 	v.AutomaticEnv()
@@ -56,6 +83,8 @@ func NewConfig(version string) Config {
 	return Config{
 		Namespaces: splitStrings(v.GetString(namespaces)),
 		Port:       v.GetInt(port),
+		Host:       v.GetString(Host),
 		TLS:        useTLS,
+		Timeout:    v.GetInt(timeout),
 	}
 }

internal/http/client.go

@@ -3,9 +3,15 @@ package http
 import (
 	"crypto/tls"
 	"errors"
+	nriK8sClient "github.com/newrelic/nri-kubernetes/src/client"
+	nriKubeletClient "github.com/newrelic/nri-kubernetes/src/kubelet/client"
+	"github.com/sirupsen/logrus"
 	"io/ioutil"
 	"net/http"
+	netHttp "net/http"
 	"net/url"
+	"os"
+	"time"
 )
 
 type HttpClient interface {
@@ -26,12 +32,13 @@ func (c *httpClient) Get(path string) ([]byte, error) {
 		return nil, err
 	}
 
+	defer resp.Body.Close()
+	buff, _ := ioutil.ReadAll(resp.Body)
+
 	if resp.StatusCode != http.StatusOK {
 		return nil, errors.New(resp.Status)
 	}
 
-	buff, _ := ioutil.ReadAll(resp.Body)
-	_ = resp.Body.Close()
 	return buff, nil
 }
 
@@ -47,3 +54,40 @@ func NewClient(url url.URL, token string) HttpClient {
 		token: token,
 	}
 }
+
+// kubeletClient addapts the nri-kubernetes kubelet client.
+type kubeletClient struct {
+	client nriK8sClient.HTTPClient
+}
+
+// NewKubeletClient creates a new kubeletClient instance.
+func NewKubeletClient(nodeName string, timeout time.Duration) (HttpClient, error) {
+	logger := logrus.New()
+	logger.SetOutput(os.Stderr)
+	d, err := nriKubeletClient.NewDiscoverer(nodeName, logger)
+	if err != nil {
+		return nil, err
+	}
+	client, err := d.Discover(timeout)
+	if err != nil {
+		return nil, err
+	}
+	return &kubeletClient{
+		client: client,
+	}, nil
+}
+
+func (kc *kubeletClient) Get(path string) ([]byte, error) {
+	resp, err := kc.client.Do(netHttp.MethodGet, path)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+	buff, _ := ioutil.ReadAll(resp.Body)
+
+	if resp.StatusCode != netHttp.StatusOK {
+		return nil, errors.New(resp.Status)
+	}
+	return buff, nil
+}

internal/kubernetes/kubelet.go

@@ -3,22 +3,23 @@ package kubernetes
 import (
 	"encoding/json"
 	"fmt"
-	"net/url"
-	"os"
-	"path/filepath"
-	"strconv"
-
+	configPkg "github.com/newrelic/nri-discovery-kubernetes/internal/config"
 	"github.com/newrelic/nri-discovery-kubernetes/internal/http"
 	"github.com/newrelic/nri-discovery-kubernetes/internal/utils"
+	"github.com/sirupsen/logrus"
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strconv"
+	"time"
 )
 
-const host = "localhost"
 const podsPath = "/pods"
 const clusterNameEnvVar = "CLUSTER_NAME"
-const kubeletHostEnvVar = "NRK8S_NODE_NAME"
+const nodeNameEnvVar = "NRK8S_NODE_NAME"
 
 type PortsMap map[string]int32
 type LabelsMap map[string]string
@@ -147,7 +148,7 @@ func getClusterName() string {
 	return clusterName
 }
 
-func NewKubelet(port int, useTLS bool) (Kubelet, error) {
+func NewKubelet(host string, port int, useTLS bool, autoConfig bool, timeout time.Duration) (Kubelet, error) {
 	config, err := rest.InClusterConfig()
 	// not inside the cluster?
 	if err != nil {
@@ -159,12 +160,26 @@ func NewKubelet(port int, useTLS bool) (Kubelet, error) {
 	}
 
 	clusterName := getClusterName()
-	kubeletHost, isKubeletHostSet := os.LookupEnv(kubeletHostEnvVar)
+	nodeName, isNodeNameSet := os.LookupEnv(nodeNameEnvVar)
+	if autoConfig && isNodeNameSet {
+		client, err := http.NewKubeletClient(nodeName, timeout)
+		if err != nil {
+			logrus.WithError(err).Warn("failed to initialize kubelet client")
+		} else {
+			kubelet := &kubelet{
+				client:      &client,
+				NodeName:    nodeName,
+				ClusterName: clusterName,
+			}
+			return kubelet, nil
+		}
+	}
 
-	if !isKubeletHostSet {
-		// If the environment variable represented by kubeletHostEnvVar is not set,
-		// fallback to the default value.
-		kubeletHost = host
+	// host provided by cmd line arg has higher precedence.
+	// if host cmd line arg is not provided use NRK8S_NODE_NAME in case is set, otherwise localhost.
+	var kubeletHost = host
+	if isNodeNameSet && !configPkg.IsFlagPassed(configPkg.Host) {
+		kubeletHost = nodeName
 	}
 
 	hostUrl := makeUrl(kubeletHost, port, useTLS)

internal/kubernetes/kubelet_test.go

@@ -6,10 +6,6 @@ import (
 	"testing"
 )
 
-func pointerToBool(b bool) *bool {
-	return &b
-}
-
 func getPod(phase v1.PodPhase, containerStatus ...v1.ContainerStatus) v1.Pod {
 	return v1.Pod{
 		Status: v1.PodStatus{
@@ -29,7 +25,6 @@ func buildContainerStatus(containerName string, containerState v1.ContainerState
 		Image:                "k8s.gcr.io/kube-scheduler:v1.18.2",
 		ImageID:              "docker-pullable://k8s.gcr.io/kube-scheduler@sha256:69f90a33b64c99e4c78e3cae36b0c767729b5a54203aa35524b1033708d1b482",
 		ContainerID:          "docker://fd5fd1918be39db9992067f87f4daa755c83adbec63aece69879fb29d45514a0",
-		Started:              pointerToBool(true),
 	}
 }