Get current resource usage of a pod in Kubernetes with Go client - go

Question

The kubernetes go client has tons of methods and I can't find how I can get the current CPU & RAM usage of a specific (or all pods).
Can someone tell me what methods I need to call to get the current usage for pods & nodes?
My NodeList:
nodes, err := clientset.CoreV1().Nodes().List(metav1.ListOptions{})
Kubernetes Go Client: https://github.com/kubernetes/client-go
Metrics package: https://github.com/kubernetes/kubernetes/tree/master/staging/src/k8s.io/metrics
As far as I got the metrics server implements the Kubernetes metrics package in order to fetch the resource usage from pods and nodes, but I couldn't figure out where & how they do it: https://github.com/kubernetes-incubator/metrics-server

Answer 1

It is correct that go-client does not have support for metrics type, but in the metrics package there is a pregenerated client that can be used for fetching metrics objects and assign them right away to the appropriate structure. The only thing you need to do first is to generate a config and pass it to metrics client. So a simple client for metrics would look like this:
package main
import (
"k8s.io/client-go/tools/clientcmd"
metrics "k8s.io/metrics/pkg/client/clientset/versioned"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)
func main() {
var kubeconfig, master string //empty, assuming inClusterConfig
config, err := clientcmd.BuildConfigFromFlags(master, kubeconfig)
if err != nil{
panic(err)
}
mc, err := metrics.NewForConfig(config)
if err != nil {
panic(err)
}
mc.MetricsV1beta1().NodeMetricses().Get("your node name", metav1.GetOptions{})
mc.MetricsV1beta1().NodeMetricses().List(metav1.ListOptions{})
mc.MetricsV1beta1().PodMetricses(metav1.NamespaceAll).List(metav1.ListOptions{})
mc.MetricsV1beta1().PodMetricses(metav1.NamespaceAll).Get("your pod name", metav1.GetOptions{})
}
Each of the above methods from metric client returns an appropriate structure (you can check those here) and an error (if any) which you should process according to your requirements.

Answer 2

here is an example.
package main
import (
"fmt"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/tools/clientcmd"
metrics "k8s.io/metrics/pkg/client/clientset/versioned"
)
func main() {
var kubeconfig, master string //empty, assuming inClusterConfig
config, err := clientcmd.BuildConfigFromFlags(master, kubeconfig)
if err != nil {
panic(err)
}
mc, err := metrics.NewForConfig(config)
if err != nil {
panic(err)
}
podMetrics, err := mc.MetricsV1beta1().PodMetricses(metav1.NamespaceAll).List(metav1.ListOptions{})
if err != nil {
fmt.Println("Error:", err)
return
}
for _, podMetric := range podMetrics.Items {
podContainers := podMetric.Containers
for _, container := range podContainers {
cpuQuantity, ok := container.Usage.Cpu().AsInt64()
memQuantity, ok := container.Usage.Memory().AsInt64()
if !ok {
return
}
msg := fmt.Sprintf("Container Name: %s \n CPU usage: %d \n Memory usage: %d", container.Name, cpuQuantity, memQuantity)
fmt.Println(msg)
}
}
}

Answer 3

The API you're looking for in new versions of Kubernetes (tested on mine as of 1.10.7) is the metrics.k8s.io/v1beta1 API route.
You can see it locally if you run a kubectl proxy and check http://localhost:8001/apis/metrics.k8s.io/v1beta1/pods and /nodes on your localhost.
I see where your confusion is though. At the time of writing, it does not look like the metrics/v1beta1 has a generated typed package (https://godoc.org/k8s.io/client-go/kubernetes/typed), and doesn't appear in the kubernetes.ClientSet object.
You can hit all available endpoints directly though the rest.RestClient object, and just specify metrics/v1beta1 as the versionedAPIPath, which will be more work and less convenient than the nicely wrapped ClientSet, but I'm not sure how long it'll take before that API shows up in that interface.