ctr: add new metrics subcommand

Signed-off-by: Samuel Karp <skarp@amazon.com>

cmd/ctr/commands/tasks/metrics.go

@@ -0,0 +1,83 @@
+// +build linux
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package tasks
+
+import (
+	"errors"
+	"fmt"
+
+	"os"
+	"text/tabwriter"
+
+	"github.com/containerd/cgroups"
+	"github.com/containerd/containerd/cmd/ctr/commands"
+	"github.com/containerd/typeurl"
+	"github.com/urfave/cli"
+)
+
+func init() {
+	// metricsCommand is only added on Linux as github.com/containerd/cgroups
+	// does not compile on darwin or windows
+	Command.Subcommands = append(Command.Subcommands, metricsCommand)
+}
+
+var metricsCommand = cli.Command{
+	Name:      "metrics",
+	Usage:     "get a single data point of metrics for a task with the built-in Linux runtime",
+	ArgsUsage: "CONTAINER",
+	Aliases:   []string{"metric"},
+	Action: func(context *cli.Context) error {
+		client, ctx, cancel, err := commands.NewClient(context)
+		if err != nil {
+			return err
+		}
+		defer cancel()
+		container, err := client.LoadContainer(ctx, context.Args().First())
+		if err != nil {
+			return err
+		}
+		task, err := container.Task(ctx, nil)
+		if err != nil {
+			return err
+		}
+		metric, err := task.Metrics(ctx)
+		if err != nil {
+			return nil
+		}
+		w := tabwriter.NewWriter(os.Stdout, 1, 8, 4, ' ', 0)
+		fmt.Fprintf(w, "ID\tTIMESTAMP\t\n")
+		fmt.Fprintf(w, "%s\t%s\t\n\n", metric.ID, metric.Timestamp)
+
+		anydata, err := typeurl.UnmarshalAny(metric.Data)
+		if err != nil {
+			return err
+		}
+		data, ok := anydata.(*cgroups.Metrics)
+		if !ok {
+			return errors.New("cannot convert metric data to cgroups.Metrics")
+		}
+		fmt.Fprintf(w, "METRIC\tVALUE\t\n")
+		fmt.Fprintf(w, "memory.usage_in_bytes\t%d\t\n", data.Memory.Usage.Usage)
+		fmt.Fprintf(w, "memory.stat.cache\t%d\t\n", data.Memory.TotalCache)
+		fmt.Fprintf(w, "cpuacct.usage\t%d\t\n", data.CPU.Usage.Total)
+		fmt.Fprintf(w, "cpuacct.usage_percpu\t%v\t\n", data.CPU.Usage.PerCPU)
+
+		return w.Flush()
+	},
+}