Add method to check for a lock's existance and force it to release if stale.

mayan/apps/document_indexing/tasks.py

@@ -74,7 +74,7 @@ def task_index_document(self, document_id):
 
 @app.task(bind=True, default_retry_delay=RETRY_DELAY, ignore_result=True)
 def task_do_rebuild_all_indexes(self):
-    if Lock.filter(name__startswith='document_indexing_task_update_index_document'):
+    if Lock.check_existing(name__startswith='document_indexing_task_update_index_document'):
         # A document index update is happening, wait
         raise self.retry()
 

mayan/apps/lock_manager/managers.py

@@ -49,3 +49,21 @@ class LockManager(models.Manager):
         else:
             logger.debug('acquired lock: %s', name)
             return lock
+
+    def check_existing(self, **kwargs):
+        try:
+            existing_lock = self.get(**kwargs)
+        except self.model.DoesNotExist:
+            return False
+        else:
+            # Lock exists, try to re-acquire it in case it is a stale lock
+            try:
+                lock = self.acquire_lock(existing_lock.name)
+            except LockError:
+                # This is expected, try to acquire it to force it to
+                # timeout in case it is a stale lock.
+                return True
+            else:
+                # Able to re-acquire anothers lock, so we release it now
+                lock.release()
+                return False