adding runner for oci package

pkg/drivers/kic/oci/runner.go

+/*
+Copyright 2019 The Kubernetes Authors All rights reserved.
+
+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 oci
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os/exec"
+	"strings"
+	"time"
+
+	"github.com/golang/glog"
+)
+
+//runner runs commands using the os/exec package.
+type runner struct {
+}
+
+// RunResult holds the results of a Runner
+type RunResult struct {
+	Stdout   bytes.Buffer
+	Stderr   bytes.Buffer
+	ExitCode int
+	Args     []string // the args that was passed to Runner
+}
+
+// Command returns a human readable command string that does not induce eye fatigue
+func (rr RunResult) Command() string {
+	var sb strings.Builder
+	sb.WriteString(rr.Args[0])
+	for _, a := range rr.Args[1:] {
+		if strings.Contains(a, " ") {
+			sb.WriteString(fmt.Sprintf(` "%s"`, a))
+			continue
+		}
+		sb.WriteString(fmt.Sprintf(" %s", a))
+	}
+	return sb.String()
+}
+
+// Output returns human-readable output for an execution result
+func (rr RunResult) Output() string {
+	var sb strings.Builder
+	if rr.Stdout.Len() > 0 {
+		sb.WriteString(fmt.Sprintf("-- stdout --\n%s\n-- /stdout --", rr.Stdout.Bytes()))
+	}
+	if rr.Stderr.Len() > 0 {
+		sb.WriteString(fmt.Sprintf("\n** stderr ** \n%s\n** /stderr **", rr.Stderr.Bytes()))
+	}
+	return sb.String()
+}
+
+// newRunner returns an oci runner
+func newRunner() *runner {
+	return &runner{}
+}
+
+// RunCmd implements the Command Runner interface to run a exec.Cmd object
+func (*runner) RunCmd(cmd *exec.Cmd) (*RunResult, error) {
+	rr := &RunResult{Args: cmd.Args}
+	glog.Infof("Run: %v", rr.Command())
+
+	var outb, errb io.Writer
+	if cmd.Stdout == nil {
+		var so bytes.Buffer
+		outb = io.MultiWriter(&so, &rr.Stdout)
+	} else {
+		outb = io.MultiWriter(cmd.Stdout, &rr.Stdout)
+	}
+
+	if cmd.Stderr == nil {
+		var se bytes.Buffer
+		errb = io.MultiWriter(&se, &rr.Stderr)
+	} else {
+		errb = io.MultiWriter(cmd.Stderr, &rr.Stderr)
+	}
+
+	cmd.Stdout = outb
+	cmd.Stderr = errb
+
+	start := time.Now()
+	err := cmd.Run()
+	elapsed := time.Since(start)
+
+	if exitError, ok := err.(*exec.ExitError); ok {
+		rr.ExitCode = exitError.ExitCode()
+	}
+	// Decrease log spam
+	if elapsed > (1 * time.Second) {
+		glog.Infof("Completed: %s: (%s)", rr.Command(), elapsed)
+	}
+	if err == nil {
+		return rr, nil
+	}
+
+	return rr, fmt.Errorf("%s: %v\nstdout:\n%s\nstderr:\n%s", rr.Command(), err, rr.Stdout.String(), rr.Stderr.String())
+}