Refactor spawn-daemon so it can be used by all OSes and make it write exit code to a file

command/spawn_daemon_linux.go

@@ -1,115 +1,16 @@
 package command
 
-import (
-	"encoding/json"
-	"fmt"
-	"os"
-	"os/exec"
-	"strconv"
-	"strings"
-	"syscall"
-)
+import "syscall"
 
-// Configuration for the command to start as a daemon.
-type DaemonConfig struct {
-	exec.Cmd
+// configureChroot enters the user command into a chroot if specified in the
+// config and on an OS that supports Chroots.
+func (c *SpawnDaemonCommand) configureChroot() {
+	if len(c.config.Chroot) != 0 {
+		if c.config.Cmd.SysProcAttr == nil {
+			c.config.Cmd.SysProcAttr = &syscall.SysProcAttr{}
+		}
 
-	// The paths, if not /dev/null, must be either in the tasks root directory
-	// or in the shared alloc directory.
-	StdoutFile string
-	StdinFile  string
-	StderrFile string
-
-	Chroot string
-}
-
-// Whether to start the user command or abort.
-type TaskStart bool
-
-func (c *SpawnDaemonCommand) Run(args []string) int {
-	flags := c.Meta.FlagSet("spawn-daemon", FlagSetClient)
-	flags.Usage = func() { c.Ui.Output(c.Help()) }
-
-	if err := flags.Parse(args); err != nil {
-		return 1
-	}
-
-	// Check that we got json input.
-	args = flags.Args()
-	if len(args) != 1 {
-		c.Ui.Error(c.Help())
-		return 1
-	}
-	jsonInput, err := strconv.Unquote(args[0])
-	if err != nil {
-		return c.outputStartStatus(fmt.Errorf("Failed to unquote json input: %v", err), 1)
-	}
-
-	// De-serialize the passed command.
-	var cmd DaemonConfig
-	dec := json.NewDecoder(strings.NewReader(jsonInput))
-	if err := dec.Decode(&cmd); err != nil {
-		return c.outputStartStatus(err, 1)
-	}
-
-	// Isolate the user process.
-	if _, err := syscall.Setsid(); err != nil {
-		return c.outputStartStatus(fmt.Errorf("Failed setting sid: %v", err), 1)
-	}
-
-	syscall.Umask(0)
-
-	// Redirect logs.
-	stdo, err := os.OpenFile(cmd.StdoutFile, os.O_CREATE|os.O_RDWR|os.O_APPEND, 0666)
-	if err != nil {
-		return c.outputStartStatus(fmt.Errorf("Error opening file to redirect Stdout: %v", err), 1)
-	}
-
-	stde, err := os.OpenFile(cmd.StderrFile, os.O_CREATE|os.O_RDWR|os.O_APPEND, 0666)
-	if err != nil {
-		return c.outputStartStatus(fmt.Errorf("Error opening file to redirect Stderr: %v", err), 1)
-	}
-
-	stdi, err := os.OpenFile(cmd.StdinFile, os.O_CREATE|os.O_RDONLY, 0666)
-	if err != nil {
-		return c.outputStartStatus(fmt.Errorf("Error opening file to redirect Stdin: %v", err), 1)
-	}
-
-	cmd.Cmd.Stdout = stdo
-	cmd.Cmd.Stderr = stde
-	cmd.Cmd.Stdin = stdi
-
-	// Chroot jail the process and set its working directory.
-	if cmd.Cmd.SysProcAttr == nil {
-		cmd.Cmd.SysProcAttr = &syscall.SysProcAttr{}
-	}
-
-	cmd.Cmd.SysProcAttr.Chroot = cmd.Chroot
-	cmd.Cmd.Dir = "/"
-
-	// Wait to get the start command.
-	var start TaskStart
-	dec = json.NewDecoder(os.Stdin)
-	if err := dec.Decode(&start); err != nil {
-		return c.outputStartStatus(err, 1)
-	}
-
-	if !start {
-		return 0
-	}
-
-	// Spawn the user process.
-	if err := cmd.Cmd.Start(); err != nil {
-		return c.outputStartStatus(fmt.Errorf("Error starting user command: %v", err), 1)
-	}
-
-	// Indicate that the command was started successfully.
-	c.outputStartStatus(nil, 0)
-
-	// Wait and then output the exit status.
-	if err := cmd.Wait(); err != nil {
-		return 1
-	}
-
-	return 0
+		c.config.Cmd.SysProcAttr.Chroot = c.config.Chroot
+		c.config.Cmd.Dir = "/"
+	}
 }