Enable session storage of initial values (#91)

* Relocate store and fetch of initial arguments into util.py

* Added flag to use session as an alternative to the cache

* Set default to cache not session for initial arguments

* Set default to cache

* Remove trailing slash

* Add tests of initial argument configuration

Author: delsim

demo/demo/settings.py

@@ -132,6 +132,8 @@
     "http_poke_enabled" : True, # Flag controlling availability of direct-to-messaging http endpoint
 
     "view_decorator" : None, # Specify a function to be used to wrap each of the dpd view functions
+
+    "cache_arguments" : True, # True for cache, False for session-based argument propagation
     }
 
 # Static files (CSS, JavaScript, Images)

django_plotly_dash/templatetags/plotly_dash.py

@@ -24,15 +24,12 @@
 
 # pylint: disable=too-many-arguments, unused-variable, unused-argument, possibly-unused-variable
 
-import uuid
-
 from django import template
-from django.core.cache import cache
 
 from django.contrib.sites.shortcuts import get_current_site
 
 from django_plotly_dash.models import DashApp
-from django_plotly_dash.util import pipe_ws_endpoint_name, cache_timeout_initial_arguments
+from django_plotly_dash.util import pipe_ws_endpoint_name, store_initial_arguments
 
 register = template.Library()
 
@@ -74,13 +71,7 @@ def plotly_app(context, name=None, slug=None, da=None, ratio=0.1, use_frameborde
     height: 100%;
     """
 
-    if initial_arguments:
-        # Generate a cache id
-        cache_id = "dpd-initial-args-%s" % str(uuid.uuid4()).replace('-', '')
-        # Store args in json form in cache
-        cache.set(cache_id, initial_arguments, cache_timeout_initial_arguments())
-    else:
-        cache_id = None
+    cache_id = store_initial_arguments(context['request'], initial_arguments)
 
     da, app = _locate_daapp(name, slug, da, cache_id=cache_id)
 

django_plotly_dash/tests.py

@@ -203,3 +203,44 @@ def test_injection_updating(client):
         assert response3.status_code == 200
 
         assert response3.content.find(b'Test 789 content') > 0
+
+@pytest.mark.django_db
+def test_argument_settings(settings, client):
+    'Test the setting that controls how initial arguments are propagated through to the dash app'
+
+    from django_plotly_dash.util import initial_argument_location, store_initial_arguments, get_initial_arguments
+
+    assert initial_argument_location()
+
+    settings.PLOTLY_DASH = {'cache_arguments': True}
+
+    assert initial_argument_location()
+
+    test_value = {"test":"first"}
+
+    cache_id = store_initial_arguments(None, test_value)
+
+    assert len(cache_id) > 10
+
+    fetched = get_initial_arguments(None, cache_id)
+
+    assert fetched == test_value
+
+    settings.PLOTLY_DASH = {'cache_arguments': False}
+
+    assert not initial_argument_location()
+
+    cache_id2 = store_initial_arguments(client, test_value)
+
+    assert len(cache_id2) > 10
+
+    assert cache_id != cache_id2
+
+    ## For some reason, sessions are continually replaced, so lookup here doesnt work
+    #fetched2 = get_initial_arguments(client, cache_id2)
+    #assert fetched2 == test_value
+
+    assert store_initial_arguments(None, None) is None
+    assert get_initial_arguments(None, None) is None
+    assert store_initial_arguments(client, None) is None
+    assert get_initial_arguments(client, None) is None

django_plotly_dash/urls.py

@@ -37,8 +37,8 @@
 
 for base_type, args, name_prefix, url_ending, name_suffix in [('instance', {}, '', '', '', ),
                                                               ('app', {'stateless':True}, 'app-', '', '', ),
-                                                              ('instance', {}, '', '/initial/<slug:cache_id>/', '--args', ),
-                                                              ('app', {'stateless':True}, 'app-', '/initial/<slug:cache_id>/', '--args', ),
+                                                              ('instance', {}, '', '/initial/<slug:cache_id>', '--args', ),
+                                                              ('app', {'stateless':True}, 'app-', '/initial/<slug:cache_id>', '--args', ),
                                                              ]:
 
     for url_part, view_function, name, url_suffix in [('_dash-routes', routes, 'routes', '', ),

django_plotly_dash/util.py

@@ -23,7 +23,10 @@
 
 '''
 
+import uuid
+
 from django.conf import settings
+from django.core.cache import cache
 
 def _get_settings():
     try:
@@ -57,3 +60,38 @@ def http_poke_endpoint_enabled():
 def cache_timeout_initial_arguments():
     'Return cache timeout, in seconds, for initial arguments'
     return _get_settings().get('cache_timeout_initial_arguments', 60)
+
+def initial_argument_location():
+    'Return True if cache to be used for setting and getting initial arguments, or False for a session'
+
+    setget_location = _get_settings().get('cache_arguments', True)
+
+    return setget_location
+
+def store_initial_arguments(request, initial_arguments=None):
+    'Store initial arguments, if any, and return a cache identifier'
+
+    if initial_arguments is None:
+        return None
+
+    # Generate a cache id
+    cache_id = "dpd-initial-args-%s" % str(uuid.uuid4()).replace('-', '')
+
+    # Store args in json form in cache
+    if initial_argument_location():
+        cache.set(cache_id, initial_arguments, cache_timeout_initial_arguments())
+    else:
+        request.session[cache_id] = initial_arguments
+
+    return cache_id
+
+def get_initial_arguments(request, cache_id=None):
+    'Extract initial arguments for the dash app'
+
+    if cache_id is None:
+        return None
+
+    if initial_argument_location():
+        return cache.get(cache_id)
+
+    return request.session[cache_id]

django_plotly_dash/views.py

@@ -27,9 +27,9 @@
 import json
 
 from django.http import HttpResponse, HttpResponseRedirect
-from django.core.cache import cache
 
 from .models import DashApp
+from .util import get_initial_arguments
 
 def routes(*args, **kwargs):
     'Return routes'
@@ -52,10 +52,7 @@ def layout(request, ident, stateless=False, cache_id=None, **kwargs):
     view_func = app.locate_endpoint_function('dash-layout')
     resp = view_func()
 
-    if cache_id:
-        initial_arguments = cache.get(cache_id)
-    else:
-        initial_arguments = None
+    initial_arguments = get_initial_arguments(request, cache_id)
 
     response_data, mimetype = app.augment_initial_layout(resp, initial_arguments)
     return HttpResponse(response_data,

docs/configuration.rst

@@ -27,6 +27,9 @@ below.
 
       # Name of view wrapping function
       "view_decorator": None,
+
+      # Flag to control location of initial argument storage
+      "cache_arguments": True,
   }
 
 Defaults are inserted for missing values. It is also permissible to not have any ``PLOTLY_DASH`` entry in
@@ -72,4 +75,12 @@ To restrict all access to logged-in users, use the ``login_required`` wrapper:
 
 More information can be found in the :ref:`view decoration <access_control>` section.
 
+.. _cache_arguments:
+
+Initial arguments
+-----------------
 
+Initial arguments are stored within the server between the specification of an app in a template tag and the invocation of the
+view functions for the app. This storage is transient and can be efficiently performed using Django's caching framework. In some
+situations, however, a suitably configured cache is not available. For this use case, setting the ``cache_arguments`` flag to ``False`` will
+cause initial arguments to be placed inside the Django session.