preload a docker image on the k3s node agents

pkg/agent/config/config.go

@@ -161,6 +161,7 @@ func get(envInfo *cmds.Agent) (*config.Node, error) {
 		ContainerRuntimeEndpoint: envInfo.ContainerRuntimeEndpoint,
 	}
 	nodeConfig.LocalAddress = localAddress(controlConfig)
+	nodeConfig.Images = filepath.Join(envInfo.DataDir, "images")
 	nodeConfig.AgentConfig.NodeIP = nodeIP
 	nodeConfig.AgentConfig.NodeName = nodeName
 	nodeConfig.AgentConfig.ClusterDNS = controlConfig.ClusterDNS

pkg/agent/containerd/containerd.go

@@ -3,9 +3,13 @@ package containerd
 import (
 	"context"
 	"fmt"
+	"github.com/containerd/containerd"
+	"github.com/containerd/containerd/namespaces"
 	"io"
+	"io/ioutil"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"syscall"
 	"time"
@@ -122,5 +126,40 @@ func Run(ctx context.Context, cfg *config.Node) error {
 		}
 	}
 
+	fileInfo, err := os.Stat(cfg.Images)
+	if err != nil {
+		logrus.Infof("Cannot find images in %s: %v", cfg.Images, err)
+	} else {
+		if fileInfo.IsDir() {
+			fileInfos, err := ioutil.ReadDir(cfg.Images)
+			if err != nil {
+				logrus.Infof("Cannot read images in %s: %v", cfg.Images, err)
+			}
+			client, err := containerd.New(cfg.Containerd.Address)
+			if err != nil {
+				return err
+			}
+			defer client.Close()
+
+			ctxContainerD := namespaces.WithNamespace(context.Background(), "k8s.io")
+
+			for _, fileInfo := range fileInfos {
+				if !fileInfo.IsDir() {
+					filePath := filepath.Join(cfg.Images, fileInfo.Name())
+					file, err := os.Open(filePath)
+					if err != nil {
+						logrus.Errorf("Unable to read %s: %v", filePath, err)
+						continue
+					}
+					logrus.Debugf("Import %s", filePath)
+					_, err = client.Import(ctxContainerD, file)
+					if err != nil {
+						logrus.Errorf("Unable to import %s: %v", filePath, err)
+					}
+				}
+			}
+		}
+	}
+
 	return nil
 }

pkg/daemons/config/types.go

@@ -16,6 +16,7 @@ type Node struct {
 	FlannelConf              string
 	LocalAddress             string
 	Containerd               Containerd
+	Images                   string
 	AgentConfig              Agent
 	CACerts                  []byte
 	ServerAddress            string