14807: Include more detail in errors.

[arvados.git] / services / crunch-run / background.go

diff --git a/services/crunch-run/background.go b/services/crunch-run/background.go
index a50853837085f6b7a6fd89bb61eba381dc9f6098..334b3ab674ee9534eb7e30c4bcd2fb700e93cc2a 100644 (file)
--- a/services/crunch-run/background.go
+++ b/services/crunch-run/background.go
@@ -49,14 +49,15 @@ func detach(uuid string, args []string, stdout, stderr io.Writer) error {
                        return nil, err
                }
                defer dirlock.Close()
-               lockfile, err := os.OpenFile(filepath.Join(lockdir, lockprefix+uuid+locksuffix), os.O_CREATE|os.O_RDWR, 0700)
+               lockfilename := filepath.Join(lockdir, lockprefix+uuid+locksuffix)
+               lockfile, err := os.OpenFile(lockfilename, os.O_CREATE|os.O_RDWR, 0700)
                if err != nil {
-                       return nil, err
+                       return nil, fmt.Errorf("open %s: %s", lockfilename, err)
                }
                err = syscall.Flock(int(lockfile.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
                if err != nil {
                        lockfile.Close()
-                       return nil, err
+                       return nil, fmt.Errorf("lock %s: %s", lockfilename, err)
                }
                return lockfile, nil
        }()
@@ -91,7 +92,7 @@ func detach(uuid string, args []string, stdout, stderr io.Writer) error {
        if err != nil {
                os.Remove(outfile.Name())
                os.Remove(errfile.Name())
-               return err
+               return fmt.Errorf("exec %s: %s", cmd.Path, err)
        }
 
        w := io.MultiWriter(stdout, lockfile)
@@ -123,14 +124,14 @@ func kill(uuid string, signal syscall.Signal, stdout, stderr io.Writer) error {
        if os.IsNotExist(err) {
                return nil
        } else if err != nil {
-               return err
+               return fmt.Errorf("open %s: %s", path, err)
        }
        defer f.Close()
 
        var pi procinfo
        err = json.NewDecoder(f).Decode(&pi)
        if err != nil {
-               return fmt.Errorf("%s: %s\n", path, err)
+               return fmt.Errorf("decode %s: %s\n", path, err)
        }
 
        if pi.UUID != uuid || pi.PID == 0 {
@@ -139,7 +140,7 @@ func kill(uuid string, signal syscall.Signal, stdout, stderr io.Writer) error {
 
        proc, err := os.FindProcess(pi.PID)
        if err != nil {
-               return err
+               return fmt.Errorf("%s: find process %d: %s", uuid, pi.PID, err)
        }
 
        err = proc.Signal(signal)
@@ -147,16 +148,19 @@ func kill(uuid string, signal syscall.Signal, stdout, stderr io.Writer) error {
                err = proc.Signal(syscall.Signal(0))
        }
        if err == nil {
-               return fmt.Errorf("pid %d: sent signal %d (%s) but process is still alive", pi.PID, signal, signal)
+               return fmt.Errorf("%s: pid %d: sent signal %d (%s) but process is still alive", uuid, pi.PID, signal, signal)
        }
-       fmt.Fprintf(stderr, "pid %d: %s\n", pi.PID, err)
+       fmt.Fprintf(stderr, "%s: pid %d: %s\n", uuid, pi.PID, err)
        return nil
 }
 
 // List UUIDs of active crunch-run processes.
 func ListProcesses(stdout, stderr io.Writer) int {
-       return exitcode(stderr, filepath.Walk(lockdir, func(path string, info os.FileInfo, err error) error {
-               if info.IsDir() {
+       // filepath.Walk does not follow symlinks, so we must walk
+       // lockdir+"/." in case lockdir itself is a symlink.
+       walkdir := lockdir + "/."
+       return exitcode(stderr, filepath.Walk(walkdir, func(path string, info os.FileInfo, err error) error {
+               if info.IsDir() && path != walkdir {
                        return filepath.SkipDir
                }
                if name := info.Name(); !strings.HasPrefix(name, lockprefix) || !strings.HasSuffix(name, locksuffix) {
@@ -186,7 +190,7 @@ func ListProcesses(stdout, stderr io.Writer) int {
                        err := os.Remove(path)
                        dirlock.Close()
                        if err != nil {
-                               fmt.Fprintln(stderr, err)
+                               fmt.Fprintf(stderr, "unlink %s: %s\n", f.Name(), err)
                        }
                        return nil
                }
@@ -224,14 +228,15 @@ func exitcode(stderr io.Writer, err error) int {
 //
 // Caller releases the lock by closing the returned file.
 func lockall() (*os.File, error) {
-       f, err := os.OpenFile(filepath.Join(lockdir, lockprefix+"all"+locksuffix), os.O_CREATE|os.O_RDWR, 0700)
+       lockfile := filepath.Join(lockdir, lockprefix+"all"+locksuffix)
+       f, err := os.OpenFile(lockfile, os.O_CREATE|os.O_RDWR, 0700)
        if err != nil {
-               return nil, err
+               return nil, fmt.Errorf("open %s: %s", lockfile, err)
        }
        err = syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
        if err != nil {
                f.Close()
-               return nil, err
+               return nil, fmt.Errorf("lock %s: %s", lockfile, err)
        }
        return f, nil
 }