Improve the implementation for UseLegacyConfig

Signed-off-by: Evan Lezar <elezar@nvidia.com>

pkg/config/engine/containerd/config_v1.go

@@ -70,9 +70,10 @@ func (c *ConfigV1) AddRuntime(name string, path string, setAsDefault bool) error
 	config.SetPath([]string{"plugins", "cri", "containerd", "runtimes", name, "options", "BinaryName"}, path)
 	config.SetPath([]string{"plugins", "cri", "containerd", "runtimes", name, "options", "Runtime"}, path)
 
-	if setAsDefault && c.UseDefaultRuntimeName {
+	if setAsDefault {
+		if !c.UseLegacyConfig {
 			config.SetPath([]string{"plugins", "cri", "containerd", "default_runtime_name"}, name)
-	} else if setAsDefault {
+		} else {
 			// Note: This is deprecated in containerd 1.4.0 and will be removed in 1.5.0
 			if config.GetPath([]string{"plugins", "cri", "containerd", "default_runtime"}) == nil {
 				config.SetPath([]string{"plugins", "cri", "containerd", "default_runtime", "runtime_type"}, c.RuntimeType)
@@ -83,6 +84,7 @@ func (c *ConfigV1) AddRuntime(name string, path string, setAsDefault bool) error
 			config.SetPath([]string{"plugins", "cri", "containerd", "default_runtime", "options", "BinaryName"}, path)
 			config.SetPath([]string{"plugins", "cri", "containerd", "default_runtime", "options", "Runtime"}, path)
 		}
+	}
 
 	*c.Tree = config
 	return nil

pkg/config/engine/containerd/containerd.go

@@ -29,8 +29,13 @@ type Config struct {
 	*toml.Tree
 	Logger               logger.Interface
 	RuntimeType          string
-	UseDefaultRuntimeName bool
 	ContainerAnnotations []string
+	// UseLegacyConfig indicates whether a config file pre v1.3 should be generated.
+	// For version 1 config prior to containerd v1.4 the default runtime was
+	// specified in a containerd.runtimes.default_runtime section.
+	// This was deprecated in v1.4 in favour of containerd.default_runtime_name.
+	// Support for this section has been removed in v2.0.
+	UseLegacyConfig bool
 }
 
 var _ engine.Interface = (*Config)(nil)
@@ -76,11 +81,11 @@ func New(opts ...Option) (engine.Interface, error) {
 		Tree:                 tomlConfig,
 		Logger:               b.logger,
 		RuntimeType:          b.runtimeType,
-		UseDefaultRuntimeName: b.useLegacyConfig,
 		ContainerAnnotations: b.containerAnnotations,
+		UseLegacyConfig:      b.useLegacyConfig,
 	}
 
-	version, err := cfg.parseVersion(b.useLegacyConfig)
+	version, err := cfg.parseVersion()
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse config version: %v", err)
 	}
@@ -95,9 +100,10 @@ func New(opts ...Option) (engine.Interface, error) {
 }
 
 // parseVersion returns the version of the config
-func (c *Config) parseVersion(useLegacyConfig bool) (int, error) {
+func (c *Config) parseVersion() (int, error) {
 	defaultVersion := 2
-	if useLegacyConfig {
+	// For legacy configs, we default to v1 configs.
+	if c.UseLegacyConfig {
 		defaultVersion = 1
 	}
 

tools/container/runtime/containerd/config_v1_test.go

@@ -94,7 +94,7 @@ func TestUpdateV1ConfigDefaultRuntime(t *testing.T) {
 			v1 := &containerd.ConfigV1{
 				Logger:          logger,
 				Tree:            cfg,
-				UseDefaultRuntimeName: !tc.legacyConfig,
+				UseLegacyConfig: tc.legacyConfig,
 				RuntimeType:     runtimeType,
 			}
 
@@ -240,7 +240,7 @@ func TestUpdateV1Config(t *testing.T) {
 			v1 := &containerd.ConfigV1{
 				Logger:               logger,
 				Tree:                 cfg,
-				UseDefaultRuntimeName: true,
+				UseLegacyConfig:      true,
 				RuntimeType:          runtimeType,
 				ContainerAnnotations: []string{"cdi.k8s.io/*"},
 			}
@@ -399,7 +399,7 @@ func TestUpdateV1ConfigWithRuncPresent(t *testing.T) {
 			v1 := &containerd.ConfigV1{
 				Logger:               logger,
 				Tree:                 cfg,
-				UseDefaultRuntimeName: true,
+				UseLegacyConfig:      true,
 				RuntimeType:          runtimeType,
 				ContainerAnnotations: []string{"cdi.k8s.io/*"},
 			}
@@ -477,7 +477,7 @@ func TestRevertV1Config(t *testing.T) {
 
 			v1 := &containerd.ConfigV1{
 				Tree:            cfg,
-				UseDefaultRuntimeName: true,
+				UseLegacyConfig: true,
 				RuntimeType:     runtimeType,
 			}
 

tools/container/runtime/containerd/containerd.go

@@ -53,7 +53,10 @@ func Flags(opts *Options) []cli.Flag {
 	flags := []cli.Flag{
 		&cli.BoolFlag{
 			Name: "use-legacy-config",
-			Usage:       "Specify whether a legacy (pre v1.3) config should be used",
+			Usage: "Specify whether a legacy (pre v1.3) config should be used. " +
+				"This ensures that a version 1 container config is created by default and that the " +
+				"containerd.runtimes.default_runtime config section is used to define the default " +
+				"runtime instead of container.default_runtime_name.",
 			Destination: &opts.useLegacyConfig,
 			EnvVars:     []string{"CONTAINERD_USE_LEGACY_CONFIG"},
 		},