Adds option for lazy connection to swift (#97)

Instead of connecting to SWIFT on storage init, this adds an option to allow the SWIFT connection to be created only when required.

Author: pomegranited

setup.py

@@ -2,7 +2,7 @@
 
 setup(
     name='django-storage-swift',
-    version='1.2.17',
+    version='1.2.18',
     description='OpenStack Swift storage backend for Django',
     long_description=open('README.rst').read(),
     url='https://github.com/dennisv/django-storage-swift',

swift/storage.py

@@ -140,9 +140,12 @@ class SwiftStorage(Storage):
     auth_token_duration = setting('SWIFT_AUTH_TOKEN_DURATION', 60 * 60 * 23)
     os_extra_options = setting('SWIFT_EXTRA_OPTIONS', {})
     auto_overwrite = setting('SWIFT_AUTO_OVERWRITE', False)
+    lazy_connect = setting('SWIFT_LAZY_CONNECT', False)
     content_type_from_fd = setting('SWIFT_CONTENT_TYPE_FROM_FD', False)
     _token_creation_time = 0
     _token = ''
+    _swift_conn = None
+    _base_url = None
     name_prefix = setting('SWIFT_NAME_PREFIX', '')
     full_listing = setting('SWIFT_FULL_LISTING', True)
     max_retries = setting('SWIFT_MAX_RETRIES', 5)
@@ -170,17 +173,28 @@ def __init__(self, **settings):
         }
         self.os_options.update(self.os_extra_options)
 
-        # Get Connection wrapper
-        self.swift_conn = swiftclient.Connection(
-            authurl=self.api_auth_url,
-            user=self.api_username,
-            key=self.api_key,
-            retries=self.max_retries,
-            tenant_name=self.tenant_name,
-            os_options=self.os_options,
-            auth_version=self.auth_version)
-
-        # Check container
+        if not self.lazy_connect:
+            self.swift_conn
+
+    @property
+    def swift_conn(self):
+        """Get swift connection wrapper"""
+        if not self._swift_conn:
+            self._swift_conn = swiftclient.Connection(
+                authurl=self.api_auth_url,
+                user=self.api_username,
+                key=self.api_key,
+                retries=self.max_retries,
+                tenant_name=self.tenant_name,
+                os_options=self.os_options,
+                auth_version=self.auth_version)
+            self._check_container()
+        return self._swift_conn
+
+    def _check_container(self):
+        """
+        Check that container exists; raises exception if not.
+        """
         try:
             self.swift_conn.head_container(self.container_name)
         except swiftclient.ClientException:
@@ -197,26 +211,30 @@ def __init__(self, **settings):
                 raise ImproperlyConfigured(
                     "Container %s does not exist." % self.container_name)
 
-        if self.auto_base_url:
-            # Derive a base URL based on the authentication information from
-            # the server, optionally overriding the protocol, host/port and
-            # potentially adding a path fragment before the auth information.
-            self.base_url = self.swift_conn.url + '/'
-            if self.override_base_url is not None:
-                # override the protocol and host, append any path fragments
-                split_derived = urlparse.urlsplit(self.base_url)
-                split_override = urlparse.urlsplit(self.override_base_url)
-                split_result = [''] * 5
-                split_result[0:2] = split_override[0:2]
-                split_result[2] = (split_override[2] + split_derived[2]
-                                   ).replace('//', '/')
-                self.base_url = urlparse.urlunsplit(split_result)
-
-            self.base_url = urlparse.urljoin(self.base_url,
-                                             self.container_name)
-            self.base_url += '/'
-        else:
-            self.base_url = self.override_base_url
+    @property
+    def base_url(self):
+        if self._base_url is None:
+            if self.auto_base_url:
+                # Derive a base URL based on the authentication information from
+                # the server, optionally overriding the protocol, host/port and
+                # potentially adding a path fragment before the auth information.
+                self._base_url = self.swift_conn.url + '/'
+                if self.override_base_url is not None:
+                    # override the protocol and host, append any path fragments
+                    split_derived = urlparse.urlsplit(self._base_url)
+                    split_override = urlparse.urlsplit(self.override_base_url)
+                    split_result = [''] * 5
+                    split_result[0:2] = split_override[0:2]
+                    split_result[2] = (split_override[2] + split_derived[2]
+                                       ).replace('//', '/')
+                    self._base_url = urlparse.urlunsplit(split_result)
+
+                self._base_url = urlparse.urljoin(self._base_url,
+                                                  self.container_name)
+                self._base_url += '/'
+            else:
+                self._base_url = self.override_base_url
+        return self._base_url
 
     def _open(self, name, mode='rb'):
         original_name = name

tests/tests.py

@@ -159,6 +159,14 @@ def test_illegal_extra_opts(self):
         with self.assertRaises(ImproperlyConfigured):
             self.default_storage('v3', os_extra_options="boom!")
 
+    @patch.object(FakeSwift.Connection, '__init__', return_value=None)
+    def test_override_lazy_connect(self, mock_swift_init):
+        """Test setting lazy_connect delays connection creation"""
+        backend = self.default_storage('v3', lazy_connect=True)
+        assert not mock_swift_init.called
+        self.assertFalse(backend.exists('warez/some_random_movie.mp4'))
+        assert mock_swift_init.called
+
 
 # @patch('swift.storage.swiftclient', new=FakeSwift)
 # class TokenTest(SwiftStorageTestCase):

tests/utils.py

@@ -91,14 +91,15 @@ class FakeSwift(object):
     containers = ['container']
 
     class Connection(object):
+        service_token = None
         def __init__(self, authurl=None, user=None, key=None, retries=5,
                      preauthurl=None, preauthtoken=None, snet=False,
                      starting_backoff=1, max_backoff=64, tenant_name=None,
                      os_options=None, auth_version="1", cacert=None,
                      insecure=False, cert=None, cert_key=None,
                      ssl_compression=True, retry_on_ratelimit=False,
                      timeout=None, session=None):
-            self.service_token = None
+            pass
 
         def _retry(self, reset_func, func, *args, **kwargs):
             self.url, self.token = self.get_auth()