feat(inputs.kube_inventory): Support using kubelet to get pods data

plugins/inputs/kube_inventory/README.md

@@ -52,6 +52,9 @@ See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
   ## If empty in-cluster config with POD's service account token will be used.
   # url = ""
 
+  ## URL for the kubelet, if set it will be used to collect the pods resource metrics
+  # url_kubelet = "http://127.0.0.1:10255"
+
   ## Namespace to use. Set to "" to use all namespaces.
   # namespace = "default"
 
@@ -112,7 +115,6 @@ list "persistentvolumes" and "nodes". You will then need to make an [aggregated
 ClusterRole][agg] that will eventually be bound to a user or group.
 
 [rbac]: https://kubernetes.io/docs/reference/access-authn-authz/rbac/
-
 [agg]: https://kubernetes.io/docs/reference/access-authn-authz/rbac/#aggregated-clusterroles
 
 ```yaml
@@ -365,11 +367,11 @@ tls_key = "/run/telegraf-kubernetes-key"
 
 The node status ready can mean 3 different values.
 
-| Tag value | Corresponding field value |  Meaning |
-| --------- | ------------------------- |  -------
-| ready     | 0                         |  NotReady|
-| ready     | 1                         |  Ready   |
-| ready     | 2                         |  Unknown |
+| Tag value | Corresponding field value | Meaning  |
+| --------- | ------------------------- | -------- |
+| ready     | 0                         | NotReady |
+| ready     | 1                         | Ready    |
+| ready     | 2                         | Unknown  |
 
 ### pv `phase_type`
 

plugins/inputs/kube_inventory/client.go

@@ -2,6 +2,7 @@ package kube_inventory
 
 import (
 	"context"
+	"net/http"
 	"time"
 
 	appsv1 "k8s.io/api/apps/v1"
@@ -12,6 +13,7 @@ import (
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
 
+	"github.com/influxdata/telegraf/config"
 	"github.com/influxdata/telegraf/plugins/common/tls"
 )
 
@@ -22,16 +24,16 @@ type client struct {
 }
 
 func newClient(baseURL, namespace, bearerTokenFile string, bearerToken string, timeout time.Duration, tlsConfig tls.ClientConfig) (*client, error) {
-	var config *rest.Config
+	var clientConfig *rest.Config
 	var err error
 
 	if baseURL == "" {
-		config, err = rest.InClusterConfig()
+		clientConfig, err = rest.InClusterConfig()
 		if err != nil {
 			return nil, err
 		}
 	} else {
-		config = &rest.Config{
+		clientConfig = &rest.Config{
 			TLSClientConfig: rest.TLSClientConfig{
 				ServerName: tlsConfig.ServerName,
 				Insecure:   tlsConfig.InsecureSkipVerify,
@@ -44,13 +46,13 @@ func newClient(baseURL, namespace, bearerTokenFile string, bearerToken string, t
 		}
 
 		if bearerTokenFile != "" {
-			config.BearerTokenFile = bearerTokenFile
+			clientConfig.BearerTokenFile = bearerTokenFile
 		} else if bearerToken != "" {
-			config.BearerToken = bearerToken
+			clientConfig.BearerToken = bearerToken
 		}
 	}
 
-	c, err := kubernetes.NewForConfig(config)
+	c, err := kubernetes.NewForConfig(clientConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -62,6 +64,21 @@ func newClient(baseURL, namespace, bearerTokenFile string, bearerToken string, t
 	}, nil
 }
 
+func newHTTPClient(tlsConfig tls.ClientConfig, bearerTokenFile string, responseTimeout config.Duration) (*http.Client, error) {
+	tlsCfg, err := tlsConfig.TLSConfig()
+	if err != nil {
+		return nil, err
+	}
+	clientConfig := &rest.Config{
+		Transport: &http.Transport{
+			TLSClientConfig: tlsCfg,
+		},
+		ContentConfig:   rest.ContentConfig{},
+		Timeout:         time.Duration(responseTimeout),
+		BearerTokenFile: bearerTokenFile,
+	}
+	return rest.HTTPClientFor(clientConfig)
+}
 func (c *client) getDaemonSets(ctx context.Context) (*appsv1.DaemonSetList, error) {
 	ctx, cancel := context.WithTimeout(ctx, c.timeout)
 	defer cancel()
@@ -107,6 +124,7 @@ func (c *client) getPersistentVolumeClaims(ctx context.Context) (*corev1.Persist
 func (c *client) getPods(ctx context.Context) (*corev1.PodList, error) {
 	ctx, cancel := context.WithTimeout(ctx, c.timeout)
 	defer cancel()
+
 	return c.CoreV1().Pods(c.namespace).List(ctx, metav1.ListOptions{})
 }
 

plugins/inputs/kube_inventory/kube_inventory.go

@@ -4,7 +4,9 @@ package kube_inventory
 import (
 	"context"
 	_ "embed"
+	"encoding/json"
 	"fmt"
+	"net/http"
 	"strconv"
 	"sync"
 	"time"
@@ -28,6 +30,7 @@ const (
 // KubernetesInventory represents the config object for the plugin.
 type KubernetesInventory struct {
 	URL               string          `toml:"url"`
+	KubeletURL        string          `toml:"url_kubelet"`
 	BearerToken       string          `toml:"bearer_token"`
 	BearerTokenString string          `toml:"bearer_token_string" deprecated:"1.24.0;use 'BearerToken' with a file instead"`
 	Namespace         string          `toml:"namespace"`
@@ -36,13 +39,13 @@ type KubernetesInventory struct {
 	ResourceInclude   []string        `toml:"resource_include"`
 	MaxConfigMapAge   config.Duration `toml:"max_config_map_age"`
 
-	SelectorInclude []string `toml:"selector_include"`
-	SelectorExclude []string `toml:"selector_exclude"`
-
-	Log telegraf.Logger `toml:"-"`
+	SelectorInclude []string        `toml:"selector_include"`
+	SelectorExclude []string        `toml:"selector_exclude"`
+	Log             telegraf.Logger `toml:"-"`
 
 	tls.ClientConfig
-	client *client
+	client     *client
+	httpClient *http.Client
 
 	selectorFilter filter.Filter
 }
@@ -67,7 +70,17 @@ func (ki *KubernetesInventory) Init() error {
 	if err != nil {
 		return err
 	}
+	if ki.ResponseTimeout < config.Duration(time.Second) {
+		ki.ResponseTimeout = config.Duration(time.Second * 5)
+	}
+	// Only create an http client if we have a kubelet url
+	if ki.KubeletURL != "" {
+		ki.httpClient, err = newHTTPClient(ki.ClientConfig, ki.BearerToken, ki.ResponseTimeout)
 
+		if err != nil {
+			ki.Log.Warnf("unable to create http client: %v", err)
+		}
+	}
 	return nil
 }
 
@@ -140,6 +153,28 @@ func (ki *KubernetesInventory) convertQuantity(s string, m float64) int64 {
 	}
 	return int64(f * m)
 }
+func (ki *KubernetesInventory) queryPodsFromKubelet(url string, v interface{}) error {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return fmt.Errorf("creating new http request for url %s failed: %w", url, err)
+	}
+
+	req.Header.Add("Accept", "application/json")
+	resp, err := ki.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("error making HTTP request to %q: %w", url, err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("%s returned HTTP status %s", url, resp.Status)
+	}
+
+	if err := json.NewDecoder(resp.Body).Decode(v); err != nil {
+		return fmt.Errorf("error parsing response: %w", err)
+	}
+
+	return nil
+}
 
 func (ki *KubernetesInventory) createSelectorFilters() error {
 	selectorFilter, err := filter.NewIncludeExcludeFilter(ki.SelectorInclude, ki.SelectorExclude)

plugins/inputs/kube_inventory/pod.go

@@ -2,6 +2,7 @@ package kube_inventory
 
 import (
 	"context"
+	"fmt"
 	"strings"
 
 	corev1 "k8s.io/api/core/v1"
@@ -10,12 +11,20 @@ import (
 )
 
 func collectPods(ctx context.Context, acc telegraf.Accumulator, ki *KubernetesInventory) {
-	list, err := ki.client.getPods(ctx)
+	var list corev1.PodList
+	listRef := &list
+	var err error
+
+	if ki.KubeletURL != "" {
+		err = ki.queryPodsFromKubelet(fmt.Sprintf("%s/pods", ki.KubeletURL), listRef)
+	} else {
+		listRef, err = ki.client.getPods(ctx)
+	}
 	if err != nil {
 		acc.AddError(err)
 		return
 	}
-	for _, p := range list.Items {
+	for _, p := range listRef.Items {
 		ki.gatherPod(p, acc)
 	}
 }

plugins/inputs/kube_inventory/sample.conf

@@ -4,6 +4,9 @@
   ## If empty in-cluster config with POD's service account token will be used.
   # url = ""
 
+  ## URL for the kubelet, if set it will be used to collect the pods resource metrics
+  # url_kubelet = "http://127.0.0.1:10255"
+
   ## Namespace to use. Set to "" to use all namespaces.
   # namespace = "default"