Initial implementation: nocs exec can run echo.

We currently depend on https://github.com/cf-guardian/specs which is a
fork of https://github.com/opencontainers/specs and which may be
superseded by the pull request
opencontainers/runtime-spec#135.

[#101501242]

Signed-off-by: Gareth Smith <gsmith@pivotal.io>

README.md

@@ -1,2 +1,5 @@
-# nocs
-A containerless implementation of the OCI Open Container Specification
+# nOCS
+A containerless implementation of the OCI Open Container Specification.
+
+This is intended for testing [runc](https://github.com/opencontainers/runc), and other
+[OCF](https://github.com/opencontainers/specs) clients without creating containers.

main.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"syscall"
+
+	"github.com/cf-guardian/specs"
+)
+
+func main() {
+	if os.Args[1] != "exec" {
+		panic("Unsupported command!")
+	}
+	config := parseConfig(configFilePath())
+
+	cmd := exec.Command(config.Process.Args[0], config.Process.Args[1:]...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	checkError(cmd.Start(), "starting process", 80)
+
+	checkWaitError(cmd.Wait(), "awaiting process completion", 85)
+}
+
+func configFilePath() string {
+	if len(os.Args) < 3 || os.Args[2] == "" {
+		pwd, err := os.Getwd()
+		checkError(err, "getting working directory", 90)
+		return path.Join(pwd, "config.json")
+	}
+	return os.Args[2]
+}
+
+func parseConfig(configPath string) *specs.Spec {
+	configStr, err := ioutil.ReadFile(configPath)
+	checkError(err, "reading config file", 95)
+
+	var config = &specs.Spec{}
+	checkError(json.Unmarshal([]byte(configStr), config), "parsing config JSON", 100)
+
+	return config
+}
+
+func checkWaitError(err error, action string, exitCode int) {
+	if err != nil {
+		if exitErr, ok := err.(*exec.ExitError); ok {
+			if waitStatus, ok := exitErr.Sys().(syscall.WaitStatus); !ok {
+				checkError(err, action+": expected a WaitStatus", exitCode)
+			} else {
+				os.Exit(waitStatus.ExitStatus())
+			}
+		}
+		checkError(err, action+": expected an ExitError", exitCode)
+	}
+}
+
+func checkError(err error, action string, exitCode int) {
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s: %s: %s\n", filepath.Base(os.Args[0]), action, err)
+		os.Exit(exitCode)
+	}
+}

nocs_suite_test.go

@@ -0,0 +1,27 @@
+package main_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+
+	"github.com/onsi/gomega/gexec"
+)
+
+var nocsBin string
+
+func TestNocs(t *testing.T) {
+	RegisterFailHandler(Fail)
+
+	SynchronizedBeforeSuite(func() []byte {
+		nocsPath, err := gexec.Build("github.com/cloudfoundry-incubator/nocs")
+		Expect(err).ToNot(HaveOccurred())
+		return []byte(nocsPath)
+	}, func(path []byte) {
+		Expect(string(path)).NotTo(BeEmpty())
+		nocsBin = string(path)
+	})
+
+	RunSpecs(t, "nOCS Suite")
+}

nocs_test.go

@@ -0,0 +1,208 @@
+package main_test
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+	"syscall"
+
+	"path/filepath"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("nOCS", func() {
+	var (
+		configFileDir string
+		nocsProcessWD string
+
+		cmd *exec.Cmd
+
+		stdout, stderr string
+		exitCode       int
+	)
+
+	BeforeEach(func() {
+		dirtyPath, err := ioutil.TempDir("", "nOCSTest")
+		Expect(err).NotTo(HaveOccurred())
+		configFileDir, err = filepath.EvalSymlinks(dirtyPath)
+		Expect(err).NotTo(HaveOccurred())
+
+		nocsProcessWD, err = os.Getwd()
+		Expect(err).NotTo(HaveOccurred())
+	})
+
+	JustBeforeEach(func() {
+		cmd.Dir = nocsProcessWD
+
+		outBuffer, errBuffer := bytes.NewBuffer([]byte{}), bytes.NewBuffer([]byte{})
+		cmd.Stdout, cmd.Stderr = outBuffer, errBuffer
+
+		Expect(cmd.Start()).To(Succeed())
+
+		exitCode = getExitCode(cmd.Wait())
+
+		stdout, stderr = outBuffer.String(), errBuffer.String()
+	})
+
+	AfterEach(func() {
+		os.RemoveAll(configFileDir)
+	})
+
+	Context("Running a simple command", func() {
+		BeforeEach(func() {
+			commandArgs := []string{"echo", "Hello OCF!"}
+			configFilePath := createConfigFile("nocs-simple.json", configFileDir, commandArgs)
+
+			cmd = exec.Command(nocsBin, "exec", configFilePath)
+		})
+
+		It("produces the appropriate stdout", func() {
+			Expect(stdout).To(Equal("Hello OCF!\n"))
+		})
+
+		It("produces the appropriate stderr", func() {
+			Expect(stderr).To(BeEmpty())
+		})
+
+		It("returns the appropriate exit status code", func() {
+			Expect(exitCode).To(Equal(0))
+		})
+	})
+
+	Context("Running a command which produces stderr", func() {
+		BeforeEach(func() {
+			commandArgs := []string{"/bin/sh", "-c", "echo Hello OCF! 1>&2"}
+			configFilePath := createConfigFile("nocs-stderr.json", configFileDir, commandArgs)
+
+			cmd = exec.Command(nocsBin, "exec", configFilePath)
+		})
+
+		It("produces the appropriate stdout", func() {
+			Expect(stdout).To(BeEmpty())
+		})
+
+		It("produces the appropriate stderr", func() {
+			Expect(stderr).To(Equal("Hello OCF!\n"))
+		})
+
+		It("returns the appropriate exit status code", func() {
+			Expect(exitCode).To(Equal(0))
+		})
+	})
+
+	Context("Running a command which exits with non-zero status", func() {
+		BeforeEach(func() {
+			commandArgs := []string{"/usr/bin/false"}
+			configFilePath := createConfigFile("nocs-errcode.json", configFileDir, commandArgs)
+
+			cmd = exec.Command(nocsBin, "exec", configFilePath)
+		})
+
+		It("returns the appropriate exit status code", func() {
+			Expect(exitCode).To(Equal(1))
+		})
+	})
+
+	Context("Running without passing a configuration filepath", func() {
+		BeforeEach(func() {
+			commandArgs := []string{"echo", "Hello default OCF!"}
+			createConfigFile("config.json", configFileDir, commandArgs)
+
+			cmd = exec.Command(nocsBin, "exec")
+
+			nocsProcessWD = configFileDir
+		})
+
+		It("produces the appropriate stdout", func() {
+			Expect(stdout).To(Equal("Hello default OCF!\n"))
+		})
+	})
+
+	Context("Running when passing the empty configuration filepath", func() {
+		BeforeEach(func() {
+			commandArgs := []string{"echo", "Hello empty OCF!"}
+			createConfigFile("config.json", configFileDir, commandArgs)
+
+			cmd = exec.Command(nocsBin, "exec", "")
+
+			nocsProcessWD = configFileDir
+		})
+
+		It("produces the appropriate stdout", func() {
+			Expect(stdout).To(Equal("Hello empty OCF!\n"))
+		})
+	})
+
+	Context("Running with a missing configuration file", func() {
+		BeforeEach(func() {
+			cmd = exec.Command(nocsBin, "exec")
+
+			nocsProcessWD = configFileDir
+		})
+
+		It("produces the appropriate stderr", func() {
+			Expect(stderr).To(Equal(filepath.Base(nocsBin) + ": reading config file: open " + filepath.Join(configFileDir, "config.json: no such file or directory\n")))
+		})
+
+		It("returns the appropriate exit status code", func() {
+			Expect(exitCode).To(Equal(95))
+		})
+
+	})
+
+	Context("Running when passing a relative configuration filepath", func() {
+		BeforeEach(func() {
+			commandArgs := []string{"echo", "Hello relative OCF!"}
+			createConfigFile("relative.json", configFileDir, commandArgs)
+			subdirPath := filepath.Join(configFileDir, "some-subdir")
+			err := os.Mkdir(subdirPath, 0777)
+			Expect(err).NotTo(HaveOccurred())
+
+			cmd = exec.Command(nocsBin, "exec", "../relative.json")
+
+			nocsProcessWD = subdirPath
+		})
+
+		It("produces the appropriate stdout", func() {
+			Expect(stdout).To(Equal("Hello relative OCF!\n"))
+		})
+	})
+})
+
+func createConfigFile(configFileName, configFileDir string, args []string) string {
+	configFilePath := path.Join(configFileDir, configFileName)
+
+	err := ioutil.WriteFile(configFilePath, []byte(
+		`{"process": {
+        "user": {
+          "uid": 1,
+          "gid": 1
+        },
+        "args": `+argsToJSON(args)+`
+     }}`), 0777)
+	Expect(err).NotTo(HaveOccurred())
+
+	return configFilePath
+}
+
+func argsToJSON(args []string) string {
+	return `["` + strings.Join(args, `","`) + `"]`
+}
+
+func getExitCode(err error) int {
+	if err != nil {
+		exitErr, ok := err.(*exec.ExitError)
+		Expect(ok).To(BeTrue())
+
+		waitStatus, ok := exitErr.Sys().(syscall.WaitStatus)
+		Expect(ok).To(BeTrue())
+
+		return waitStatus.ExitStatus()
+	}
+	return 0
+}