Merge pull request #2626 from krsoninikhil/defaults3

Uses namespace labels for default options

client.go

@@ -136,6 +136,20 @@ func New(address string, opts ...ClientOpt) (*Client, error) {
 	if copts.services == nil && c.conn == nil {
 		return nil, errors.New("no grpc connection or services is available")
 	}
+
+	// check namespace labels for default runtime
+	if copts.defaultRuntime == "" && copts.defaultns != "" {
+		namespaces := c.NamespaceService()
+		ctx := context.Background()
+		if labels, err := namespaces.Labels(ctx, copts.defaultns); err == nil {
+			if defaultRuntime, ok := labels[defaults.DefaultRuntimeNSLabel]; ok {
+				c.runtime = defaultRuntime
+			}
+		} else {
+			return nil, err
+		}
+	}
+
 	return c, nil
 }
 
@@ -152,6 +166,20 @@ func NewWithConn(conn *grpc.ClientConn, opts ...ClientOpt) (*Client, error) {
 		conn:    conn,
 		runtime: fmt.Sprintf("%s.%s", plugin.RuntimePlugin, runtime.GOOS),
 	}
+
+	// check namespace labels for default runtime
+	if copts.defaultRuntime == "" && copts.defaultns != "" {
+		namespaces := c.NamespaceService()
+		ctx := context.Background()
+		if labels, err := namespaces.Labels(ctx, copts.defaultns); err == nil {
+			if defaultRuntime, ok := labels[defaults.DefaultRuntimeNSLabel]; ok {
+				c.runtime = defaultRuntime
+			}
+		} else {
+			return nil, err
+		}
+	}
+
 	if copts.services != nil {
 		c.services = *copts.services
 	}

client_test.go

@@ -28,6 +28,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/containerd/containerd/defaults"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/namespaces"
@@ -396,3 +397,29 @@ func createShimDebugConfig() string {
 
 	return f.Name()
 }
+
+func TestDefaultRuntimeWithNamespaceLabels(t *testing.T) {
+	client, err := newClient(t, address)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.Close()
+
+	ctx, cancel := testContext()
+	defer cancel()
+	namespaces := client.NamespaceService()
+	testRuntime := "testRuntime"
+	runtimeLabel := defaults.DefaultRuntimeNSLabel
+	if err := namespaces.SetLabel(ctx, testNamespace, runtimeLabel, testRuntime); err != nil {
+		t.Fatal(err)
+	}
+
+	testClient, err := New(address, WithDefaultNamespace(testNamespace))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer testClient.Close()
+	if testClient.runtime != testRuntime {
+		t.Error("failed to set default runtime from namespace labels")
+	}
+}

container_opts.go

@@ -20,7 +20,9 @@ import (
 	"context"
 
 	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/defaults"
 	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/oci"
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/snapshots"
@@ -107,7 +109,7 @@ func WithSnapshotter(name string) NewContainerOpts {
 // WithSnapshot uses an existing root filesystem for the container
 func WithSnapshot(id string) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
-		setSnapshotterIfEmpty(c)
+		setSnapshotterIfEmpty(ctx, client, c)
 		// check that the snapshot exists, if not, fail on creation
 		if _, err := client.SnapshotService(c.Snapshotter).Mounts(ctx, id); err != nil {
 			return err
@@ -125,7 +127,7 @@ func WithNewSnapshot(id string, i Image, opts ...snapshots.Opt) NewContainerOpts
 		if err != nil {
 			return err
 		}
-		setSnapshotterIfEmpty(c)
+		setSnapshotterIfEmpty(ctx, client, c)
 		parent := identity.ChainID(diffIDs).String()
 		if _, err := client.SnapshotService(c.Snapshotter).Prepare(ctx, id, parent, opts...); err != nil {
 			return err
@@ -155,7 +157,7 @@ func WithNewSnapshotView(id string, i Image, opts ...snapshots.Opt) NewContainer
 		if err != nil {
 			return err
 		}
-		setSnapshotterIfEmpty(c)
+		setSnapshotterIfEmpty(ctx, client, c)
 		parent := identity.ChainID(diffIDs).String()
 		if _, err := client.SnapshotService(c.Snapshotter).View(ctx, id, parent, opts...); err != nil {
 			return err
@@ -166,9 +168,18 @@ func WithNewSnapshotView(id string, i Image, opts ...snapshots.Opt) NewContainer
 	}
 }
 
-func setSnapshotterIfEmpty(c *containers.Container) {
+func setSnapshotterIfEmpty(ctx context.Context, client *Client, c *containers.Container) {
 	if c.Snapshotter == "" {
-		c.Snapshotter = DefaultSnapshotter
+		defaultSnapshotter := DefaultSnapshotter
+		namespaceService := client.NamespaceService()
+		if ns, err := namespaces.NamespaceRequired(ctx); err == nil {
+			if labels, err := namespaceService.Labels(ctx, ns); err == nil {
+				if snapshotLabel, ok := labels[defaults.DefaultSnapshotterNSLabel]; ok {
+					defaultSnapshotter = snapshotLabel
+				}
+			}
+		}
+		c.Snapshotter = defaultSnapshotter
 	}
 }
 

container_opts_unix.go

@@ -50,7 +50,7 @@ func withRemappedSnapshotBase(id string, i Image, uid, gid uint32, readonly bool
 			return err
 		}
 
-		setSnapshotterIfEmpty(c)
+		setSnapshotterIfEmpty(ctx, client, c)
 
 		var (
 			snapshotter = client.SnapshotService(c.Snapshotter)

defaults/defaults.go

@@ -23,4 +23,10 @@ const (
 	// DefaultMaxSendMsgSize defines the default maximum message size for
 	// sending protobufs passed over the GRPC API.
 	DefaultMaxSendMsgSize = 16 << 20
+	// DefaultRuntimeNSLabel defines the namespace label to check for
+	// default runtime
+	DefaultRuntimeNSLabel = "containerd.io/defaults/runtime"
+	// DefaultSnapshotterNSLabel defines the namespances label to check for
+	// default snapshotter
+	DefaultSnapshotterNSLabel = "containerd.io/defaults/snapshotter"
 )

docs/namespaces.md

@@ -34,9 +34,7 @@ Filesystem paths, IDs, and other system level resources must be namespaced for a
 
 Simply create a new `context` and set your application's namespace on the `context`.
 Make sure to use a unique namespace for applications that does not conflict with existing namespaces. The namespaces
-API, or the `ctr namespaces` client command, can be used to query/list and create new namespaces. Note that namespaces
+API, or the `ctr namespaces` client command, can be used to query/list and create new namespaces.
-can have a list of labels associated with the namespace. This can be useful for associating metadata with a particular
-namespace.
 
 ```go
 ctx := context.Background()
@@ -49,6 +47,19 @@ var (
 )
 ```
 
+## Namespace Labels
+
+Namespaces can have a list of labels associated with the namespace. This can be useful for associating metadata with a particular namespace.
+Labels can also be used to configure the defaults for containerd, for example:
+
+```bash
+> sudo ctr namespaces label k8s.io containerd.io/defaults/snapshotter=btrfs
+> sudo ctr namespaces label k8s.io containerd.io/defaults/runtime=testRuntime
+```
+
+This will set the default snapshotter as `btrfs` and runtime as `testRuntime`.
+Note that currently only these two labels are used to configure the defaults and labels of `default` namespace are not considered for the same.
+
 ## Inspecting Namespaces
 
 If we need to inspect containers, images, or other resources in various namespaces the `ctr` tool allows you to do this.