Address comments.

Signed-off-by: Lantao Liu <lantaol@google.com>

docs/config.md

@@ -66,8 +66,11 @@ The explanation and default value of each configuration item are as follows:
     # conf_template is the file path of golang template used to generate
     # cni config.
     # If this is set, containerd will generate a cni config file from the
-    # template. Otherwise, containerd will wait for the system admin or pod
-    # network addon to drop the config file into the conf_dir.
+    # template. Otherwise, containerd will wait for the system admin or cni
+    # daemon to drop the config file into the conf_dir.
+    # This is a temporary backward-compatible solution for kubenet users
+    # who don't have a cni daemonset in production yet.
+    # This will be deprecated when kubenet is deprecated.
     conf_template = ""
 
   # "plugins.cri.registry" contains config related to the registry

pkg/config/config.go

@@ -47,12 +47,14 @@ type CniConfig struct {
 	NetworkPluginConfDir string `toml:"conf_dir" json:"confDir"`
 	// NetworkPluginConfTemplate is the file path of golang template used to generate
 	// cni config.
-	// Usually the cni config should be placed by system admin or pod network
-	// addons like calico, weaveworks etc. However, in some cases only a simple cni
-	// config is needed with pod cidr dynamically set.
-	// NetworkPluginConfTemplate can be used in those cases. When it is set,
-	// containerd will get cidr from kubelet to replace {{.PodCIDR}} in the template,
-	// and write the config into NetworkPluginConfDir.
+	// When it is set, containerd will get cidr from kubelet to replace {{.PodCIDR}} in
+	// the template, and write the config into NetworkPluginConfDir.
+	// Ideally the cni config should be placed by system admin or cni daemon like calico,
+	// weaveworks etc. However, there are still users using kubenet
+	// (https://kubernetes.io/docs/concepts/cluster-administration/network-plugins/#kubenet)
+	// today, who don't have a cni daemonset in production. NetworkPluginConfTemplate is
+	// a temporary backward-compatible solution for them.
+	// TODO(random-liu): Deprecate this option when kubenet is deprecated.
 	NetworkPluginConfTemplate string `toml:"conf_template" json:"confTemplate"`
 }
 

pkg/server/testing/fake_cni_plugin.go

@@ -23,6 +23,7 @@ import (
 // FakeCNIPlugin is a fake plugin used for test.
 type FakeCNIPlugin struct {
 	StatusErr error
+	LoadErr   error
 }
 
 // NewFakeCNIPlugin create a FakeCNIPlugin.
@@ -47,5 +48,5 @@ func (f *FakeCNIPlugin) Status() error {
 
 // Load loads the network config.
 func (f *FakeCNIPlugin) Load(opts ...cni.LoadOption) error {
-	return nil
+	return f.LoadErr
 }

pkg/server/update_runtime_config.go

@@ -21,6 +21,7 @@ import (
 	"path/filepath"
 	"text/template"
 
+	cni "github.com/containerd/go-cni"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
@@ -44,16 +45,17 @@ func (c *criService) UpdateRuntimeConfig(ctx context.Context, r *runtime.UpdateR
 		return &runtime.UpdateRuntimeConfigResponse{}, nil
 	}
 	confTemplate := c.config.NetworkPluginConfTemplate
-	if err := c.netPlugin.Status(); err == nil {
-		if confTemplate != "" {
-			logrus.Infof("Network plugin is ready, skip generating cni config from template %q", confTemplate)
-		}
-		return &runtime.UpdateRuntimeConfigResponse{}, nil
-	}
 	if confTemplate == "" {
 		logrus.Info("No cni config template is specified, wait for other system components to drop the config.")
 		return &runtime.UpdateRuntimeConfigResponse{}, nil
 	}
+	if err := c.netPlugin.Status(); err == nil {
+		logrus.Infof("Network plugin is ready, skip generating cni config from template %q", confTemplate)
+		return &runtime.UpdateRuntimeConfigResponse{}, nil
+	} else if err := c.netPlugin.Load(cni.WithLoNetwork(), cni.WithDefaultConf()); err == nil {
+		logrus.Infof("CNI config is successfully loaded, skip generating cni config from template %q", confTemplate)
+		return &runtime.UpdateRuntimeConfigResponse{}, nil
+	}
 	logrus.Infof("Generating cni config from template %q", confTemplate)
 	// generate cni config file from the template with updated pod cidr.
 	t, err := template.ParseFiles(confTemplate)

pkg/server/update_runtime_config_test.go

@@ -125,6 +125,7 @@ func TestUpdateRuntimeConfig(t *testing.T) {
 			}
 			if !test.networkReady {
 				c.netPlugin.(*servertesting.FakeCNIPlugin).StatusErr = errors.New("random error")
+				c.netPlugin.(*servertesting.FakeCNIPlugin).LoadErr = errors.New("random error")
 			}
 			_, err = c.UpdateRuntimeConfig(context.Background(), req)
 			assert.NoError(t, err)