Add support for conditional image tarball imports

Normally K3s will import all tarballs in the image dir on startup, and
re-import any tarballs that change while it is running.

This change allows users to opt into only importing tarballs that have
changed since they were last imported, even across restarts.

This behavior is opted into by touching a `.cache.json` file in the
images dir. This file is used to track the size and mtime of the image
files when they are imported.

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>

Author: brandond

pkg/agent/containerd/containerd.go

@@ -10,7 +10,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
-	"time"
 
 	containerd "github.com/containerd/containerd/v2/client"
 	"github.com/containerd/containerd/v2/core/images"
@@ -139,7 +138,6 @@ func PreloadImages(ctx context.Context, cfg *config.Node) error {
 		return err
 	}
 	defer criConn.Close()
-	imageClient := runtimeapi.NewImageServiceClient(criConn)
 
 	// Ensure that our images are imported into the correct namespace
 	ctx = namespaces.WithNamespace(ctx, criK8sContainerdNamespace)
@@ -154,44 +152,7 @@ func PreloadImages(ctx context.Context, cfg *config.Node) error {
 		return pkgerrors.WithMessage(err, "failed to clear pinned labels")
 	}
 
-	go watchImages(ctx, cfg)
-
-	// After setting the watcher, connections and everything, k3s will see if the images folder is already created
-	// if the folder its already created, it will load the images
-	fileInfo, err := os.Stat(cfg.Images)
-	if os.IsNotExist(err) {
-		return nil
-	} else if err != nil {
-		logrus.Errorf("Unable to find images in %s: %v", cfg.Images, err)
-		return nil
-	}
-
-	if !fileInfo.IsDir() {
-		return nil
-	}
-
-	fileInfos, err := os.ReadDir(cfg.Images)
-	if err != nil {
-		logrus.Errorf("Unable to read images in %s: %v", cfg.Images, err)
-		return nil
-	}
-
-	for _, fileInfo := range fileInfos {
-		if fileInfo.IsDir() {
-			continue
-		}
-
-		start := time.Now()
-		filePath := filepath.Join(cfg.Images, fileInfo.Name())
-
-		if err := preloadFile(ctx, cfg, client, imageClient, filePath); err != nil {
-			logrus.Errorf("Error encountered while importing %s: %v", filePath, err)
-			continue
-		}
-		logrus.Infof("Imported images from %s in %s", filePath, time.Since(start))
-	}
-
-	return nil
+	return importAndWatchImages(ctx, cfg)
 }
 
 // preloadFile handles loading images from a single tarball or pre-pull image list.