Port over supervisor to use grpc shim

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

supervisor/shim.go

@@ -0,0 +1,44 @@
+package supervisor
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"os/exec"
+	"path/filepath"
+	"time"
+
+	"github.com/docker/containerd/api/shim"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/grpclog"
+)
+
+func newShimClient(root string) (shim.ShimClient, error) {
+	// TODO: start the shim process
+	cmd := exec.Command("containerd-shim")
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+	cmd.Dir = root
+
+	socket := filepath.Join(root, "shim.sock")
+	return connectToShim(socket)
+}
+
+func connectToShim(socket string) (shim.ShimClient, error) {
+	// reset the logger for grpc to log to dev/null so that it does not mess with our stdio
+	grpclog.SetLogger(log.New(ioutil.Discard, "", log.LstdFlags))
+	dialOpts := []grpc.DialOption{grpc.WithInsecure(), grpc.WithTimeout(100 * time.Second)}
+	dialOpts = append(dialOpts,
+		grpc.WithDialer(func(addr string, timeout time.Duration) (net.Conn, error) {
+			return net.DialTimeout("unix", socket, timeout)
+		},
+		))
+	// FIXME: probably need a retry here
+	conn, err := grpc.Dial(fmt.Sprintf("unix://%s", socket), dialOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return shim.NewShimClient(conn), nil
+}