Updated the ocr app to use the lock manager

apps/ocr/tasks.py

@@ -4,9 +4,10 @@ from time import sleep
 from random import random
 
 from django.db.models import Q
-from django.core.cache import get_cache
 
 from job_processor.api import process_job
+from lock_manager.models import Lock
+from lock_manager.exceptions import LockError
 
 from ocr.api import do_document_ocr
 from ocr.literals import QUEUEDOCUMENT_STATE_PENDING, \
@@ -21,36 +22,13 @@ from ocr.conf.settings import QUEUE_PROCESSING_INTERVAL
 LOCK_EXPIRE = 60 * 10  # Lock expires in 10 minutes
 # TODO: Tie LOCK_EXPIRATION with hard task timeout
 
-if CACHE_URI:
-    try:
-        cache_backend = get_cache(CACHE_URI)
-    except ImportError:
-        # TODO: display or log error
-        cache_backend = None
-else:
-    cache_backend = None
-
-
-def random_delay():
-    sleep(random() * (QUEUE_PROCESSING_INTERVAL - 1))
-    return True
-
-
-if cache_backend:
-    acquire_lock = lambda lock_id: cache_backend.add(lock_id, u'true', LOCK_EXPIRE)
-    release_lock = lambda lock_id: cache_backend.delete(lock_id)
-else:
-    acquire_lock = lambda lock_id: True
-    release_lock = lambda lock_id: True
-
-
 def task_process_queue_document(queue_document_id):
     lock_id = u'%s-lock-%d' % (u'task_process_queue_document', queue_document_id)
-    if acquire_lock(lock_id):
+    try:
+        lock = Lock.objects.acquire_lock(lock_id, LOCK_EXPIRE)
         queue_document = QueueDocument.objects.get(pk=queue_document_id)
         queue_document.state = QUEUEDOCUMENT_STATE_PROCESSING
         queue_document.node_name = platform.node()
-        #queue_document.result = task_process_queue_document.request.id
         queue_document.save()
         try:
             do_document_ocr(queue_document)
@@ -59,7 +37,10 @@ def task_process_queue_document(queue_document_id):
             queue_document.state = QUEUEDOCUMENT_STATE_ERROR
             queue_document.result = e
             queue_document.save()
-        release_lock(lock_id)
+        
+        lock.release()
+    except LockError:
+        pass
 
 
 def reset_orphans():
@@ -89,8 +70,6 @@ def reset_orphans():
 
 
 def task_process_document_queues():
-    if not cache_backend:
-        random_delay()
     # reset_orphans()
     # Causes problems with big clusters increased latency
     # Disabled until better solution
@@ -108,8 +87,7 @@ def task_process_document_queues():
 
                 if oldest_queued_document_qs:
                     oldest_queued_document = oldest_queued_document_qs.order_by('datetime_submitted')[0]
-                    #task_process_queue_document.delay(oldest_queued_document.pk)
-                    #task_process_queue_document(oldest_queued_document.pk)
                     process_job(task_process_queue_document, oldest_queued_document.pk)
             except Exception, e:
-                print 'DocumentQueueWatcher exception: %s' % e
+                pass
+                #print 'DocumentQueueWatcher exception: %s' % e