checkpoint: support checkpoint ls command

Implement `nerdctl checkpoint ls` command to list checkpoints for a container,
matching Docker's output format with "CHECKPOINT NAME" header.

Signed-off-by: ChengyuZhu6 <[email protected]>

Author: ChengyuZhu6

cmd/nerdctl/checkpoint/checkpoint.go

@@ -34,7 +34,15 @@ func Command() *cobra.Command {
 
 	cmd.AddCommand(
 		CreateCommand(),
+		checkpointLsCommand(),
 	)
 
 	return cmd
 }
+
+func checkpointLsCommand() *cobra.Command {
+	x := ListCommand()
+	x.Use = "ls"
+	x.Aliases = []string{"list"}
+	return x
+}

cmd/nerdctl/checkpoint/checkpoint_list.go

@@ -0,0 +1,94 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package checkpoint
+
+import (
+	"fmt"
+	"text/tabwriter"
+
+	"github.com/containerd/nerdctl/v2/cmd/nerdctl/completion"
+	"github.com/containerd/nerdctl/v2/cmd/nerdctl/helpers"
+	"github.com/containerd/nerdctl/v2/pkg/api/types"
+	"github.com/containerd/nerdctl/v2/pkg/clientutil"
+	"github.com/containerd/nerdctl/v2/pkg/cmd/checkpoint"
+	"github.com/spf13/cobra"
+)
+
+func ListCommand() *cobra.Command {
+	var cmd = &cobra.Command{
+		Use:               "list [OPTIONS] CONTAINER",
+		Short:             "List checkpoints for a container",
+		Args:              cobra.ExactArgs(1),
+		RunE:              listAction,
+		ValidArgsFunction: listShellComplete,
+		SilenceUsage:      true,
+		SilenceErrors:     true,
+	}
+	cmd.Flags().String("checkpoint-dir", "", "Checkpoint directory")
+	return cmd
+}
+
+func processListFlags(cmd *cobra.Command) (types.CheckpointListOptions, error) {
+	globalOptions, err := helpers.ProcessRootCmdFlags(cmd)
+	if err != nil {
+		return types.CheckpointListOptions{}, err
+	}
+
+	checkpointDir, err := cmd.Flags().GetString("checkpoint-dir")
+	if err != nil {
+		return types.CheckpointListOptions{}, err
+	}
+	if checkpointDir == "" {
+		checkpointDir = globalOptions.DataRoot + "/checkpoints"
+	}
+
+	return types.CheckpointListOptions{
+		Stdout:        cmd.OutOrStdout(),
+		GOptions:      globalOptions,
+		CheckpointDir: checkpointDir,
+	}, nil
+}
+
+func listAction(cmd *cobra.Command, args []string) error {
+	listOptions, err := processListFlags(cmd)
+	if err != nil {
+		return err
+	}
+	client, ctx, cancel, err := clientutil.NewClient(cmd.Context(), listOptions.GOptions.Namespace, listOptions.GOptions.Address)
+	if err != nil {
+		return err
+	}
+	defer cancel()
+
+	checkpoints, err := checkpoint.List(ctx, client, args[0], listOptions)
+	if err != nil {
+		return err
+	}
+
+	w := tabwriter.NewWriter(listOptions.Stdout, 4, 8, 4, ' ', 0)
+	fmt.Fprintln(w, "CHECKPOINT NAME")
+
+	for _, cp := range checkpoints {
+		fmt.Fprintln(w, cp.Name)
+	}
+
+	return w.Flush()
+}
+
+func listShellComplete(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+	return completion.ImageNames(cmd)
+}

pkg/api/types/checkpoint_types.go

@@ -27,3 +27,15 @@ type CheckpointCreateOptions struct {
 	// Checkpoint directory
 	CheckpointDir string
 }
+
+type CheckpointListOptions struct {
+	Stdout   io.Writer
+	GOptions GlobalCommandOptions
+	// Checkpoint directory
+	CheckpointDir string
+}
+
+type CheckpointSummary struct {
+	// Name is the name of the checkpoint.
+	Name string
+}

pkg/cmd/checkpoint/list.go

@@ -0,0 +1,75 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package checkpoint
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	containerd "github.com/containerd/containerd/v2/client"
+
+	"github.com/containerd/nerdctl/v2/pkg/api/types"
+	"github.com/containerd/nerdctl/v2/pkg/checkpointutil"
+	"github.com/containerd/nerdctl/v2/pkg/idutil/containerwalker"
+)
+
+func List(ctx context.Context, client *containerd.Client, containerID string, options types.CheckpointListOptions) ([]types.CheckpointSummary, error) {
+	var container containerd.Container
+	var out []types.CheckpointSummary
+
+	walker := &containerwalker.ContainerWalker{
+		Client: client,
+		OnFound: func(ctx context.Context, found containerwalker.Found) error {
+			if found.MatchCount > 1 {
+				return fmt.Errorf("multiple containers found with provided prefix: %s", found.Req)
+			}
+			container = found.Container
+			return nil
+		},
+	}
+
+	n, err := walker.Walk(ctx, containerID)
+	if err != nil {
+		return nil, err
+	} else if n == 0 {
+		return nil, fmt.Errorf("error list checkpoint for container: %s, no such container", containerID)
+	}
+
+	checkpointDir, err := checkpointutil.GetCheckpointDir(options.CheckpointDir, "", container.ID(), false)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := os.MkdirAll(checkpointDir, 0o755); err != nil {
+		return nil, err
+	}
+
+	dirs, err := os.ReadDir(checkpointDir)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, d := range dirs {
+		if !d.IsDir() {
+			continue
+		}
+		out = append(out, types.CheckpointSummary{Name: d.Name()})
+	}
+
+	return out, nil
+}