pkg/cli/admin/upgrade/channel: Add 'oc adm upgrade channel ...'

A new subcommand for conveniently managing channels.  Example
workflow, starting in a channel:

  $ oc adm upgrade
  Cluster version is 4.6.0-fc.3

  Upstream: https://api.openshift.com/api/upgrades_info/v1/graph
  Channel: candidate-4.6 (choices: candidate-4.6)
  Updates:

  VERSION    IMAGE
  4.6.0-fc.4 quay.io/openshift-release-dev/ocp-release@sha256:960ec73733150827076cbb5fa2c1f5aaa9a94bfbce1b4897e46432a56ac976c1
  4.6.0-fc.5 quay.io/openshift-release-dev/ocp-release@sha256:5883d0db15939484bd477147e6949c53fbc6f551ec20a0f1106b8a3acfb86ef8

Trying to change to the same channel is a no-op:

  $ oc adm upgrade channel candidate-4.6
  info: Cluster is already in candidate-4.6

Trying to change to an unrecognized channel gets a warning:

  $ oc adm upgrade channel does-not-exist
  error: the requested channel "does-not-exist" is not one of the available channels (candidate-4.6), you must pass --allow-explicit-channel to continue
  $ oc adm upgrade channel --allow-explicit-channel does-not-exist
  warning: The requested channel "does-not-exist" is not one of the available channels (candidate-4.6).  You have used --allow-explicit-channel to proceed anyway.
  $ oc adm upgrade
  Cluster version is 4.6.0-fc.3

  Channel: does-not-exist
  warning: Cannot display available updates:
    Reason: VersionNotFound
    Message: Unable to retrieve available updates: currently reconciling cluster version 4.6.0-fc.3 not found in the "does-not-exist" channel

When we have no known channels, changing requires no override:

  $ oc adm upgrade channel does-not-exist-either
  warning: No channels known to be compatible with the current version "4.6.0-fc.3"; unable to validate "does-not-exist-either".
  $ oc adm upgrade channel candidate-4.6
  warning: No channels known to be compatible with the current version "4.6.0-fc.3"; unable to validate "candidate-4.6".

Clearing a known channel needs an explicit override:

  $ oc adm upgrade channel
  error: the requested channel "" is not one of the available channels (candidate-4.6), you must pass --allow-explicit-channel to continue
  $ oc adm upgrade channel --allow-explicit-channel
  warning: Clearing channel "candidate-4.6"; cluster will no longer request available update recommendations.
  $ oc adm upgrade
  Cluster version is 4.6.0-fc.3

  warning: Cannot display available updates:
    Reason: NoChannel
    Message: The update channel has not been configured.

Trying to re-clear the channel is a no-op:

  $ oc adm upgrade channel
  info: Cluster channel is already clear

And you can set any channel from a cleared channel without an
override, because this is another case where we have no idea what the
valid choices are:

  $ oc adm upgrade channel candidate-4.6
  warning: No channels known to be compatible with the current version "4.6.0-fc.3"; unable to validate "candidate-4.6".
  $ oc adm upgrade
  Cluster version is 4.6.0-fc.3

  Upstream: https://api.openshift.com/api/upgrades_info/v1/graph
  Channel: candidate-4.6 (choices: candidate-4.6)
  Updates:

  VERSION    IMAGE
  4.6.0-fc.4 quay.io/openshift-release-dev/ocp-release@sha256:960ec73733150827076cbb5fa2c1f5aaa9a94bfbce1b4897e46432a56ac976c1
  4.6.0-fc.5 quay.io/openshift-release-dev/ocp-release@sha256:5883d0db15939484bd477147e6949c53fbc6f551ec20a0f1106b8a3acfb86ef8

Clearing from an unknown channel does not require an override either:

  $ oc adm upgrade channel --allow-explicit-channel does-not-exist
  warning: The requested channel "does-not-exist" is not one of the available channels (candidate-4.6).  You have used --allow-explicit-channel to proceed anyway.
  $ oc adm upgrade channel
  warning: Clearing channel "does-not-exist"; cluster will no longer request available update recommendations.

Completions updated with:

  $ hack/update-generated-completions.sh

contrib/completions/bash/oc

@@ -6873,13 +6873,74 @@ _oc_adm_uncordon()
     noun_aliases=()
 }
 
+_oc_adm_upgrade_channel()
+{
+    last_command="oc_adm_upgrade_channel"
+
+    command_aliases=()
+
+    commands=()
+
+    flags=()
+    two_word_flags=()
+    local_nonpersistent_flags=()
+    flags_with_completion=()
+    flags_completion=()
+
+    flags+=("--allow-explicit-channel")
+    local_nonpersistent_flags+=("--allow-explicit-channel")
+    flags+=("--as=")
+    two_word_flags+=("--as")
+    flags+=("--as-group=")
+    two_word_flags+=("--as-group")
+    flags+=("--cache-dir=")
+    two_word_flags+=("--cache-dir")
+    flags+=("--certificate-authority=")
+    two_word_flags+=("--certificate-authority")
+    flags+=("--client-certificate=")
+    two_word_flags+=("--client-certificate")
+    flags+=("--client-key=")
+    two_word_flags+=("--client-key")
+    flags+=("--cluster=")
+    two_word_flags+=("--cluster")
+    flags+=("--context=")
+    two_word_flags+=("--context")
+    flags+=("--insecure-skip-tls-verify")
+    flags+=("--kubeconfig=")
+    two_word_flags+=("--kubeconfig")
+    flags+=("--match-server-version")
+    flags+=("--namespace=")
+    two_word_flags+=("--namespace")
+    flags_with_completion+=("--namespace")
+    flags_completion+=("__oc_get_namespaces")
+    two_word_flags+=("-n")
+    flags_with_completion+=("-n")
+    flags_completion+=("__oc_get_namespaces")
+    flags+=("--request-timeout=")
+    two_word_flags+=("--request-timeout")
+    flags+=("--server=")
+    two_word_flags+=("--server")
+    two_word_flags+=("-s")
+    flags+=("--tls-server-name=")
+    two_word_flags+=("--tls-server-name")
+    flags+=("--token=")
+    two_word_flags+=("--token")
+    flags+=("--user=")
+    two_word_flags+=("--user")
+
+    must_have_one_flag=()
+    must_have_one_noun=()
+    noun_aliases=()
+}
+
 _oc_adm_upgrade()
 {
     last_command="oc_adm_upgrade"
 
     command_aliases=()
 
     commands=()
+    commands+=("channel")
 
     flags=()
     two_word_flags=()

contrib/completions/zsh/oc

@@ -6973,13 +6973,74 @@ _oc_adm_uncordon()
     noun_aliases=()
 }
 
+_oc_adm_upgrade_channel()
+{
+    last_command="oc_adm_upgrade_channel"
+
+    command_aliases=()
+
+    commands=()
+
+    flags=()
+    two_word_flags=()
+    local_nonpersistent_flags=()
+    flags_with_completion=()
+    flags_completion=()
+
+    flags+=("--allow-explicit-channel")
+    local_nonpersistent_flags+=("--allow-explicit-channel")
+    flags+=("--as=")
+    two_word_flags+=("--as")
+    flags+=("--as-group=")
+    two_word_flags+=("--as-group")
+    flags+=("--cache-dir=")
+    two_word_flags+=("--cache-dir")
+    flags+=("--certificate-authority=")
+    two_word_flags+=("--certificate-authority")
+    flags+=("--client-certificate=")
+    two_word_flags+=("--client-certificate")
+    flags+=("--client-key=")
+    two_word_flags+=("--client-key")
+    flags+=("--cluster=")
+    two_word_flags+=("--cluster")
+    flags+=("--context=")
+    two_word_flags+=("--context")
+    flags+=("--insecure-skip-tls-verify")
+    flags+=("--kubeconfig=")
+    two_word_flags+=("--kubeconfig")
+    flags+=("--match-server-version")
+    flags+=("--namespace=")
+    two_word_flags+=("--namespace")
+    flags_with_completion+=("--namespace")
+    flags_completion+=("__oc_get_namespaces")
+    two_word_flags+=("-n")
+    flags_with_completion+=("-n")
+    flags_completion+=("__oc_get_namespaces")
+    flags+=("--request-timeout=")
+    two_word_flags+=("--request-timeout")
+    flags+=("--server=")
+    two_word_flags+=("--server")
+    two_word_flags+=("-s")
+    flags+=("--tls-server-name=")
+    two_word_flags+=("--tls-server-name")
+    flags+=("--token=")
+    two_word_flags+=("--token")
+    flags+=("--user=")
+    two_word_flags+=("--user")
+
+    must_have_one_flag=()
+    must_have_one_noun=()
+    noun_aliases=()
+}
+
 _oc_adm_upgrade()
 {
     last_command="oc_adm_upgrade"
 
     command_aliases=()
 
     commands=()
+    commands+=("channel")
 
     flags=()
     two_word_flags=()

pkg/cli/admin/upgrade/channel/channel.go

@@ -0,0 +1,127 @@
+// Package channel contains a command for setting a cluster's update channel.
+package channel
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	configv1client "github.com/openshift/client-go/config/clientset/versioned"
+	"github.com/spf13/cobra"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/cli-runtime/pkg/genericclioptions"
+	kcmdutil "k8s.io/kubectl/pkg/cmd/util"
+	"k8s.io/kubectl/pkg/util/templates"
+)
+
+func NewOptions(streams genericclioptions.IOStreams) *Options {
+	return &Options{
+		IOStreams: streams,
+	}
+}
+
+func New(f kcmdutil.Factory, streams genericclioptions.IOStreams) *cobra.Command {
+	o := NewOptions(streams)
+	cmd := &cobra.Command{
+		Use:   "channel CHANNEL",
+		Short: "Set or clear the update channel",
+		Long: templates.LongDesc(`
+			Set or clear the update channel.
+
+			This command will set or clear the update channel, which impacts the list of updates
+			recommended for the cluster.
+
+			If there is a list of acceptable channels and the desired channel is not in that list,
+			you must pass --allow-explicit-channel to allow channel change to proceed.
+		`),
+		Run: func(cmd *cobra.Command, args []string) {
+			kcmdutil.CheckErr(o.Complete(f, cmd, args))
+			kcmdutil.CheckErr(o.Run())
+		},
+	}
+	flags := cmd.Flags()
+	flags.BoolVar(&o.AllowExplicitChannel, "allow-explicit-channel", o.AllowExplicitChannel, "Change the channel, even if there is a list of acceptable channels and the desired channel is not in that list.")
+	return cmd
+}
+
+type Options struct {
+	genericclioptions.IOStreams
+
+	Channel string
+
+	AllowExplicitChannel bool
+
+	Client configv1client.Interface
+}
+
+func (o *Options) Complete(f kcmdutil.Factory, cmd *cobra.Command, args []string) error {
+	if len(args) > 1 {
+		return kcmdutil.UsageErrorf(cmd, "multiple positional arguments given")
+	} else if len(args) == 1 {
+		o.Channel = args[0]
+	}
+
+	cfg, err := f.ToRESTConfig()
+	if err != nil {
+		return err
+	}
+	client, err := configv1client.NewForConfig(cfg)
+	if err != nil {
+		return err
+	}
+	o.Client = client
+	return nil
+}
+
+func (o *Options) Run() error {
+	ctx := context.TODO()
+	cv, err := o.Client.ConfigV1().ClusterVersions().Get(ctx, "version", metav1.GetOptions{})
+	if err != nil {
+		if errors.IsNotFound(err) {
+			return fmt.Errorf("no cluster version information available - you must be connected to an OpenShift version 4 server to fetch the current version")
+		}
+		return err
+	}
+
+	if o.Channel == cv.Spec.Channel {
+		if cv.Spec.Channel == "" {
+			fmt.Fprint(o.Out, "info: Cluster channel is already clear\n")
+		} else {
+			fmt.Fprintf(o.Out, "info: Cluster is already in %s\n", cv.Spec.Channel)
+		}
+		return nil
+	}
+
+	if len(cv.Status.Desired.Channels) > 0 {
+		found := false
+		for _, channel := range cv.Status.Desired.Channels {
+			if channel == o.Channel {
+				found = true
+				break
+			}
+		}
+		if !found {
+			if !o.AllowExplicitChannel {
+				return fmt.Errorf("the requested channel %q is not one of the available channels (%s), you must pass --allow-explicit-channel to continue\n", o.Channel, strings.Join(cv.Status.Desired.Channels, ", "))
+			}
+			if o.Channel != "" {
+				fmt.Fprintf(o.ErrOut, "warning: The requested channel %q is not one of the available channels (%s).  You have used --allow-explicit-channel to proceed anyway.\n", o.Channel, strings.Join(cv.Status.Desired.Channels, ", "))
+			}
+		}
+	} else if o.Channel != "" {
+		fmt.Fprintf(o.ErrOut, "warning: No channels known to be compatible with the current version %q; unable to validate %q.\n", cv.Status.Desired.Version, o.Channel)
+	}
+
+	if o.Channel == "" {
+		fmt.Fprintf(o.ErrOut, "warning: Clearing channel %q; cluster will no longer request available update recommendations.\n", cv.Spec.Channel)
+	}
+
+	cv.Spec.Channel = o.Channel
+
+	if _, err = o.Client.ConfigV1().ClusterVersions().Update(ctx, cv, metav1.UpdateOptions{}); err != nil {
+		return fmt.Errorf("unable to set channel: %w", err)
+	}
+
+	return nil
+}

pkg/cli/admin/upgrade/upgrade.go

@@ -22,6 +22,8 @@ import (
 	configv1 "github.com/openshift/api/config/v1"
 	configv1client "github.com/openshift/client-go/config/clientset/versioned"
 	imagereference "github.com/openshift/library-go/pkg/image/reference"
+
+	"github.com/openshift/oc/pkg/cli/admin/upgrade/channel"
 )
 
 func NewOptions(streams genericclioptions.IOStreams) *Options {
@@ -83,6 +85,9 @@ func New(f kcmdutil.Factory, streams genericclioptions.IOStreams) *cobra.Command
 	flags.BoolVar(&o.Force, "force", o.Force, "Forcefully upgrade the cluster even when upgrade release image validation fails and the cluster is reporting errors.")
 	flags.BoolVar(&o.AllowExplicitUpgrade, "allow-explicit-upgrade", o.AllowExplicitUpgrade, "Upgrade even if the upgrade target is not listed in the available versions list.")
 	flags.BoolVar(&o.AllowUpgradeWithWarnings, "allow-upgrade-with-warnings", o.AllowUpgradeWithWarnings, "Upgrade even if an upgrade is in process or a cluster error is blocking the update.")
+
+	cmd.AddCommand(channel.New(f, streams))
+
 	return cmd
 }