kubernetes / client-go

Client Configuration

Configuring the client library to connect to a Kubernetes cluster is essential for any application that needs to interact with the API. ^1 This outline describes the available configuration options and how to use them effectively.

Client Configuration Options

  • In-cluster Authentication: Configure a client running inside the Kubernetes cluster by using the Service Account token mounted at /var/run/secrets/kubernetes.io/serviceaccount. ^2
  • Out-of-cluster Authentication: Configure a client to access a Kubernetes cluster from outside. ^2 This can be done by using the kubeconfig file that contains context information about the cluster. ^3
  • Fake Client: Use a fake client in tests. ^4
  • Managing Resources with API: Create, get, update, or delete a Deployment resource using the dynamic package. ^5

Auth Plugins

Several plugins are available for obtaining credentials from external sources. To enable these plugins in your program, import them in your main package. ^1

  • All Auth Plugins:
import _ "k8s.io/client-go/plugin/pkg/client/auth"
  • Specific Auth Plugins:
import _ "k8s.io/client-go/plugin/pkg/client/auth/azure"
          import _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
          import _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"

Client Configuration API

The ClientConfig interface provides methods for retrieving and managing configuration settings. ^6

// ClientConfig is used to make it easy to get an api server client
          type ClientConfig interface {
              // RawConfig returns the merged result of all overrides
              RawConfig() (clientcmdapi.Config, error)
              // ClientConfig returns a complete client config
              ClientConfig() (*restclient.Config, error)
              // Namespace returns the namespace resulting from the merged
              // result of all overrides and a boolean indicating if it was
              // overridden
              Namespace() (string, bool, error)
              // ConfigAccess returns the rules for loading/persisting the config.
              ConfigAccess() ConfigAccess
          }

Configuration Access

The ConfigAccess interface is used to access and persist client configuration settings. ^7

// ConfigAccess implements ClientConfig
          func (config *DirectClientConfig) ConfigAccess() ConfigAccess {
              return config.configAccess
          }

Direct Client Configuration

The DirectClientConfig struct represents a client configuration that is backed by a clientcmdapi.Config and overrides. ^8

// DirectClientConfig is a ClientConfig interface that is backed by a clientcmdapi.Config, options overrides, and an optional fallbackReader for auth information
          type DirectClientConfig struct {
              config         clientcmdapi.Config
              contextName    string
              overrides      *ConfigOverrides
              fallbackReader io.Reader
              configAccess   ConfigAccess
              // promptedCredentials store the credentials input by the user
              promptedCredentials promptedCredentials
          }

Client Configuration Loading Rules

The ClientConfigLoadingRules struct defines the rules for loading and persisting configuration settings. ^9

// GetStartingConfig implements ConfigAccess
          func (rules *ClientConfigLoadingRules) GetStartingConfig() (*clientcmdapi.Config, error) {
              clientConfig := NewNonInteractiveDeferredLoadingClientConfig(rules, &ConfigOverrides{})
              rawConfig, err := clientConfig.RawConfig()
              if os.IsNotExist(err) {
                  return clientcmdapi.NewConfig(), nil
              }
              if err != nil {
                  return nil, err
              }
          
              return &rawConfig, nil
          }

References

Top-Level Directory Explanations

applyconfigurations/ - This directory contains examples and tests for applying Kubernetes configurations using the client-go library.

discovery/ - This directory contains code related to service discovery in Kubernetes.

dynamic/ - This directory contains code for working with dynamic resources in the Kubernetes API.

examples/ - This directory contains example usage of the client-go library.

gentype/ - This directory contains generated Go types for the Kubernetes API.

informers/ - This directory contains code for caching Kubernetes resources using informers.

kubernetes/ - This directory contains the main package for the client-go library, which provides types and functions for interacting with the Kubernetes API.

listers/ - This directory contains interfaces and implementations for listing Kubernetes resources.

metadata/ - This directory contains code related to metadata in Kubernetes.

openapi/ - This directory contains OpenAPI definitions for the Kubernetes API.

pkg/ - This directory contains compiled Go packages for the client-go library.

plugin/ - This directory contains code for loading plugins for the client-go library.

rest/ - This directory contains code for working with the REST API in the client-go library.

scale/ - This directory contains code for working with scale and autoscaling in Kubernetes.

tools/ - This directory contains various tools for working with the client-go library.

util/ - This directory contains utility functions for the client-go library.