X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/5bc5b8c150860a22d7a66b14aedddf30e270c7b6..437d0dc1dfeea7b81999caa1c540da0903df87f7:/lib/crunchrun/background.go

diff --git a/lib/crunchrun/background.go b/lib/crunchrun/background.go
index bf039afa0a..8a919bc5e2 100644
--- a/lib/crunchrun/background.go
+++ b/lib/crunchrun/background.go
@@ -36,10 +36,10 @@ type procinfo struct {
 //
 // Stdout and stderr in the child process are sent to the systemd
 // journal using the systemd-cat program.
-func Detach(uuid string, prog string, args []string, stdout, stderr io.Writer) int {
-	return exitcode(stderr, detach(uuid, prog, args, stdout, stderr))
+func Detach(uuid string, prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int {
+	return exitcode(stderr, detach(uuid, prog, args, stdin, stdout))
 }
-func detach(uuid string, prog string, args []string, stdout, stderr io.Writer) error {
+func detach(uuid string, prog string, args []string, stdin io.Reader, stdout io.Writer) error {
 	lockfile, err := func() (*os.File, error) {
 		// We must hold the dir-level lock between
 		// opening/creating the lockfile and acquiring LOCK_EX
@@ -77,20 +77,24 @@ func detach(uuid string, prog string, args []string, stdout, stderr io.Writer) e
 		// invoked as "/path/to/crunch-run"
 		execargs = append([]string{prog}, execargs...)
 	}
-	execargs = append([]string{
-		// Here, if the inner systemd-cat can't exec
-		// crunch-run, it writes an error message to stderr,
-		// and the outer systemd-cat writes it to the journal
-		// where the operator has a chance to discover it. (If
-		// we only used one systemd-cat command, it would be
-		// up to us to report the error -- but we are going to
-		// detach and exit, not wait for something to appear
-		// on stderr.)  Note these systemd-cat calls don't
-		// result in additional processes -- they just connect
-		// stderr/stdout to sockets and call exec().
-		"systemd-cat", "--identifier=crunch-run",
-		"systemd-cat", "--identifier=crunch-run",
-	}, execargs...)
+	if _, err := exec.LookPath("systemd-cat"); err == nil {
+		execargs = append([]string{
+			// Here, if the inner systemd-cat can't exec
+			// crunch-run, it writes an error message to
+			// stderr, and the outer systemd-cat writes it
+			// to the journal where the operator has a
+			// chance to discover it. (If we only used one
+			// systemd-cat command, it would be up to us
+			// to report the error -- but we are going to
+			// detach and exit, not wait for something to
+			// appear on stderr.)  Note these systemd-cat
+			// calls don't result in additional processes
+			// -- they just connect stderr/stdout to
+			// sockets and call exec().
+			"systemd-cat", "--identifier=crunch-run",
+			"systemd-cat", "--identifier=crunch-run",
+		}, execargs...)
+	}
 
 	cmd := exec.Command(execargs[0], execargs[1:]...)
 	// Child inherits lockfile.
@@ -99,10 +103,26 @@ func detach(uuid string, prog string, args []string, stdout, stderr io.Writer) e
 	// from parent (sshd) while sending lockfile content to
 	// caller.
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	// We need to manage our own OS pipe here to ensure the child
+	// process reads all of our stdin pipe before we return.
+	piper, pipew, err := os.Pipe()
+	if err != nil {
+		return err
+	}
+	defer pipew.Close()
+	cmd.Stdin = piper
 	err = cmd.Start()
 	if err != nil {
 		return fmt.Errorf("exec %s: %s", cmd.Path, err)
 	}
+	_, err = io.Copy(pipew, stdin)
+	if err != nil {
+		return err
+	}
+	err = pipew.Close()
+	if err != nil {
+		return err
+	}
 
 	w := io.MultiWriter(stdout, lockfile)
 	return json.NewEncoder(w).Encode(procinfo{
@@ -132,7 +152,7 @@ func kill(uuid string, signal syscall.Signal, stdout, stderr io.Writer) error {
 	var pi procinfo
 	err = json.NewDecoder(f).Decode(&pi)
 	if err != nil {
-		return fmt.Errorf("decode %s: %s\n", path, err)
+		return fmt.Errorf("decode %s: %s", path, err)
 	}
 
 	if pi.UUID != uuid || pi.PID == 0 {
@@ -162,7 +182,7 @@ func kill(uuid string, signal syscall.Signal, stdout, stderr io.Writer) error {
 	return nil
 }
 
-// List UUIDs of active crunch-run processes.
+// ListProcesses lists UUIDs of active crunch-run processes.
 func ListProcesses(stdout, stderr io.Writer) int {
 	// filepath.Walk does not follow symlinks, so we must walk
 	// lockdir+"/." in case lockdir itself is a symlink.
@@ -218,6 +238,24 @@ func ListProcesses(stdout, stderr io.Writer) int {
 			return nil
 		}
 
+		proc, err := os.FindProcess(pi.PID)
+		if err != nil {
+			// FindProcess should have succeeded, even if the
+			// process does not exist.
+			fmt.Fprintf(stderr, "%s: find process %d: %s", path, pi.PID, err)
+			return nil
+		}
+		err = proc.Signal(syscall.Signal(0))
+		if err != nil {
+			// Process is dead, even though lockfile was
+			// still locked. Most likely a stuck arv-mount
+			// process that inherited the lock from
+			// crunch-run. Report container UUID as
+			// "stale".
+			fmt.Fprintln(stdout, pi.UUID, "stale")
+			return nil
+		}
+
 		fmt.Fprintln(stdout, pi.UUID)
 		return nil
 	}))