Replace lockfile with reference lock

Updates content service to handle lock errors and return
them to the client. The client remote handler has been
updated to retry when a resource is locked until the
resource is unlocked or the expected resource exists.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

content/locks.go

@@ -3,54 +3,35 @@ package content
 import (
 	"sync"
 
-	"github.com/nightlyone/lockfile"
 	"github.com/pkg/errors"
 )
 
-// In addition to providing inter-process locks for content ingest, we also
-// define a global in process lock to prevent two goroutines writing to the
-// same file.
-//
-// This is pretty unsophisticated for now. In the future, we'd probably like to
-// have more information about who is holding which locks, as well as better
-// error reporting.
+// Handles locking references
+// TODO: use boltdb for lock status
 
 var (
-	errLocked = errors.New("key is locked")
-
-	// locks lets us lock in process, as well as output of process.
-	locks   = map[lockfile.Lockfile]struct{}{}
+	// locks lets us lock in process
+	locks   = map[string]struct{}{}
 	locksMu sync.Mutex
 )
 
-func tryLock(lock lockfile.Lockfile) error {
+func tryLock(ref string) error {
 	locksMu.Lock()
 	defer locksMu.Unlock()
 
-	if _, ok := locks[lock]; ok {
-		return errLocked
+	if _, ok := locks[ref]; ok {
+		return errors.Wrapf(ErrLocked, "key %s is locked", ref)
 	}
 
-	if err := lock.TryLock(); err != nil {
-		if errors.Cause(err) == lockfile.ErrBusy {
-			return errLocked
-		}
-
-		return errors.Wrapf(err, "lock.TryLock() encountered an error")
-	}
-
-	locks[lock] = struct{}{}
+	locks[ref] = struct{}{}
 	return nil
 }
 
-func unlock(lock lockfile.Lockfile) error {
+func unlock(ref string) {
 	locksMu.Lock()
 	defer locksMu.Unlock()
 
-	if _, ok := locks[lock]; !ok {
-		return nil
+	if _, ok := locks[ref]; ok {
+		delete(locks, ref)
 	}
-
-	delete(locks, lock)
-	return lock.Unlock()
 }