How to Correctly Execute a Command in a Kubernetes Pod Using the Go Client and Handle SPDY Connections?

Exec Command in a Kubernetes Pod Using Go Client

Issue:

The provided code snippet attempts to execute a command inside a pod using the Kubernetes Go client but encounters an error when attempting to stream the command output.

Solution:

The issue lies in the usage of remotecommand.NewExecutor(), which is intended for HTTP/1.1 connections. For SPDY connections, which are typically used in Kubernetes clusters, you should instead use remotecommand.NewSPDYExecutor().

Modified Code:

import (
    "fmt"
    "io"
    "os"

    container "k8s.io/api/core/v1"
    meta "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/client-go/kubernetes"
    restclient "k8s.io/client-go/rest"
    cmd "k8s.io/client-go/tools/remotecommand"
)

func main() {
    // Replace with your own config or use in-cluster config
    config := &restclient.Config{
        Host: "https://192.168.8.175:8080",
        // Insecure if using a self-signed certificate
        Insecure: true,
    }

    // Create a Kubernetes client
    client, err := kubernetes.NewForConfig(config)
    if err != nil {
        fmt.Println(err)
        return
    }

    // Define the pod and container to execute the command in
    podName := "wordpress-mysql-213049546-29s7d"
    namespace := "default"
    containerName := "mysql"

    // Define the command to execute
    command := []string{"ls"}

    // Create the PodExecOptions object
    execOptions := container.PodExecOptions{
        Container: containerName,
        Command:   []string{"ls"},
        Stdin:     true,
        Stdout:    true,
        Stderr:    true,
    }

    // Create the request
    req := client.CoreV1().RESTClient().Post().Resource("pods").Namespace(namespace).Name(podName).SubResource("exec")

    // Pass the PodExecOptions object as VersionedParams
    request := req.VersionedParams(&execOptions, meta.ParameterCodec)

    // Execute the command
    exec, err := cmd.NewSPDYExecutor(config, "POST", request.URL())
    if err != nil {
        fmt.Println(err)
        return
    }

    // Stream the output of the command to stdout and stderr
    err = exec.Stream(cmd.StreamOptions{
        Stdin:  os.Stdin,
        Stdout: os.Stdout,
        Stderr: os.Stderr,
    })
    if err != nil {
        fmt.Println(err)
        return
    }
}

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