Cache: Beta stage

Add retry to race condition in intermediate image generation.

Remove DB index from cache file size field.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/documents/api_views.py

@@ -38,7 +38,6 @@ from .serializers import (
     WritableDocumentTypeSerializer, WritableDocumentVersionSerializer
 )
 from .settings import settings_document_page_image_cache_time
-from .storages import storage_documentimagecache
 from .tasks import task_generate_document_page_image
 
 logger = logging.getLogger(__name__)
@@ -234,7 +233,6 @@ class APIDocumentPageImageView(generics.RetrieveAPIView):
         )
 
         cache_filename = task.get(timeout=DOCUMENT_IMAGE_TASK_TIMEOUT)
-        #with storage_documentimagecache.open(cache_filename) as file_object:
         with self.get_object().cache_partition.get_file(filename=cache_filename).open() as file_object:
             response = HttpResponse(file_object.read(), content_type='image')
             if '_hash' in request.GET: