runv: implement ps command

The PS command is currently limited by the runv-containerd
interfacer. Until runv and hyperstart is refactored, print out
the information that the current design can support.

Signed-off-by: Antonios Motakis <antonios.motakis@huawei.com>

Author: tvelocity

main.go

@@ -152,6 +152,7 @@ func main() {
 		execCommand,
 		killCommand,
 		listCommand,
+		psCommand,
 		runCommand,
 		specCommand,
 		startCommand,

ps.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"text/tabwriter"
+
+	"github.com/hyperhq/runv/containerd/api/grpc/types"
+	"github.com/urfave/cli"
+	netcontext "golang.org/x/net/context"
+)
+
+var psCommand = cli.Command{
+	Name:      "ps",
+	Usage:     "ps displays the processes running inside a container",
+	ArgsUsage: `<container-id> [ps options]`, Flags: []cli.Flag{
+		cli.StringFlag{
+			Name:  "format, f",
+			Value: "table",
+			Usage: `select one of: ` + formatOptions,
+		},
+	},
+	Action: func(context *cli.Context) error {
+		container := context.Args().First()
+		if container == "" {
+			return cli.NewExitError("container id cannot be empty", -1)
+		}
+		c, err := getContainerApi(context, container)
+		if err != nil {
+			return cli.NewExitError(fmt.Sprintf("can't access container, %v", err), -1)
+		}
+
+		switch context.String("format") {
+		case "table":
+			w := tabwriter.NewWriter(os.Stdout, 12, 1, 3, ' ', 0)
+			fmt.Fprint(w, "PROCESS\tCMD\n")
+			// we are limited by the containerd interface for now
+			for _, p := range c.Processes {
+				fmt.Fprintf(w, "%s\t%s\n",
+					p.Pid,
+					p.Args)
+			}
+			if err := w.Flush(); err != nil {
+				fatal(err)
+			}
+		case "json":
+			pids := make([]string, 0)
+			for _, p := range c.Processes {
+				pids = append(pids, p.Pid)
+			}
+
+			data, err := json.Marshal(pids)
+			if err != nil {
+				fatal(err)
+			}
+			os.Stdout.Write(data)
+			return nil
+		default:
+			return cli.NewExitError(fmt.Sprintf("invalid format option"), -1)
+		}
+
+		return nil
+	},
+}
+
+func getContainerApi(context *cli.Context, container string) (*types.Container, error) {
+	api, err := getClient(filepath.Join(context.GlobalString("root"), container, "namespace/namespaced.sock"))
+	if err != nil {
+		return nil, fmt.Errorf("failed to get client: %v", err)
+	}
+
+	s, err := api.State(netcontext.Background(), &types.StateRequest{Id: container})
+	if err != nil {
+		return nil, fmt.Errorf("get container state failed, %v", err)
+	}
+
+	for _, c := range s.Containers {
+		if c.Id == container {
+			return c, nil
+		}
+	}
+
+	return nil, fmt.Errorf("container %s not found", container)
+}