Cache shim v2 exec.LookPath results

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

runtime/v2/shim/util.go

@@ -24,6 +24,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/containerd/containerd/namespaces"
@@ -32,6 +33,8 @@ import (
 
 const shimBinaryFormat = "containerd-shim-%s-%s"
 
+var runtimePaths sync.Map
+
 // Command returns the shim command with the provided args and configuration
 func Command(ctx context.Context, runtime, containerdAddress, path string, cmdArgs ...string) (*exec.Cmd, error) {
 	ns, err := namespaces.NamespaceRequired(ctx)
@@ -52,19 +55,30 @@ func Command(ctx context.Context, runtime, containerdAddress, path string, cmdAr
 	if name == "" {
 		return nil, fmt.Errorf("invalid runtime name %s, correct runtime name should format like io.containerd.runc.v1", runtime)
 	}
+
 	var cmdPath string
-	var lerr error
+	cmdPathI, cmdPathFound := runtimePaths.Load(name)
-	if cmdPath, lerr = exec.LookPath(name); lerr != nil {
+	if cmdPathFound {
-		if eerr, ok := lerr.(*exec.Error); ok {
+		cmdPath = cmdPathI.(string)
-			if eerr.Err == exec.ErrNotFound {
+	} else {
-				return nil, errors.Wrapf(os.ErrNotExist, "runtime %q binary not installed %q", runtime, name)
+		var lerr error
+		if cmdPath, lerr = exec.LookPath(name); lerr != nil {
+			if eerr, ok := lerr.(*exec.Error); ok {
+				if eerr.Err == exec.ErrNotFound {
+					return nil, errors.Wrapf(os.ErrNotExist, "runtime %q binary not installed %q", runtime, name)
+				}
 			}
 		}
+		cmdPath, err = filepath.Abs(cmdPath)
+		if err != nil {
+			return nil, err
+		}
+		if cmdPathI, cmdPathFound = runtimePaths.LoadOrStore(name, cmdPath); cmdPathFound {
+			// We didn't store cmdPath we loaded an already cached value. Use it.
+			cmdPath = cmdPathI.(string)
+		}
 	}
-	cmdPath, err = filepath.Abs(cmdPath)
+
-	if err != nil {
-		return nil, err
-	}
 	cmd := exec.Command(cmdPath, args...)
 	cmd.Dir = path
 	cmd.Env = append(os.Environ(), "GOMAXPROCS=2")

vendor.conf

@@ -33,7 +33,7 @@ golang.org/x/sync 450f422ab23cf9881c94e2db30cac0eb1b7cf80c
 github.com/BurntSushi/toml a368813c5e648fee92e5f6c30e3944ff9d5e8895
 github.com/grpc-ecosystem/go-grpc-prometheus 6b7015e65d366bf3f19b2b2a000a831940f0f7e0
 github.com/Microsoft/go-winio v0.4.11
-github.com/Microsoft/hcsshim v0.8.1
+github.com/Microsoft/hcsshim v0.8.2
 google.golang.org/genproto d80a6e20e776b0b17a324d0ba1ab50a39c8e8944
 golang.org/x/text 19e51611da83d6be54ddafce4a4af510cb3e9ea4
 github.com/containerd/ttrpc 2a805f71863501300ae1976d29f0454ae003e85a

vendor/github.com/Microsoft/hcsshim/pkg/go-runhcs/runhcs.go

@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"sync/atomic"
 
 	irunhcs "github.com/Microsoft/hcsshim/internal/runhcs"
 	"github.com/containerd/go-runc"
@@ -23,10 +24,35 @@ const (
 	Text Format = "text"
 	// JSON is the JSON formatted log output.
 	JSON Format = "json"
-
-	command = "runhcs"
 )
 
+var runhcsPath atomic.Value
+
+func getCommandPath() string {
+	const command = "runhcs.exe"
+
+	pathi := runhcsPath.Load()
+	if pathi == nil {
+		path, err := exec.LookPath(command)
+		if err != nil {
+			// Failed to look up command just use it directly and let the
+			// Windows loader find it.
+			path = command
+			runhcsPath.Store(path)
+			return path
+		}
+		apath, err := filepath.Abs(path)
+		if err != nil {
+			// We couldnt make `path` an `AbsPath`. Just use `path` directly and
+			// let the Windows loader find it.
+			apath = path
+		}
+		runhcsPath.Store(apath)
+		return apath
+	}
+	return pathi.(string)
+}
+
 var bytesBufferPool = sync.Pool{
 	New: func() interface{} {
 		return bytes.NewBuffer(nil)
@@ -84,7 +110,7 @@ func (r *Runhcs) args() []string {
 }
 
 func (r *Runhcs) command(context context.Context, args ...string) *exec.Cmd {
-	cmd := exec.CommandContext(context, command, append(r.args(), args...)...)
+	cmd := exec.CommandContext(context, getCommandPath(), append(r.args(), args...)...)
 	cmd.Env = os.Environ()
 	return cmd
 }