Workflows: Refactor workflow preview generation

Refactor the workflow preview generation to work as a
background task API service. Solves GitLab issue #532.

The image generation runs as an out of process task
ensuring that the HTTP request is never compromised.

A new task queue named "document_states_fast" was created.
The settings WORKFLOWS_IMAGE_CACHE_TIME,
WORKFLOWS_IMAGE_CACHE_STORAGE_BACKEND,
WORKFLOWS_IMAGE_CACHE_STORAGE_BACKEND_ARGUMENTS we added.

Images generated are stored by default under /mayan/media/workflows.

The Dockerfile and deployment instructions are updated
to include the new queue.

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

HISTORY.rst

@@ -100,6 +100,10 @@
 - Refactored the workflow preview generation to work as an
   background task API service. Solves GitLab issue #532.
   A new task queue named "document_states_fast" was created.
+  The settings WORKFLOWS_IMAGE_CACHE_TIME,
+  WORKFLOWS_IMAGE_CACHE_STORAGE_BACKEND,
+  WORKFLOWS_IMAGE_CACHE_STORAGE_BACKEND_ARGUMENTS we added.
+
 
 3.1.9 (2018-11-01)
 ==================

docs/releases/3.2.rst

@@ -80,6 +80,7 @@ Bugs fixed or issues closed
 * :gitlab-issue:`487` gnupg1 Issue with Ubuntu 16.04 - Could not show/view documents
 * :gitlab-issue:`498` Can't scan subdirectories
 * :gitlab-issue:`522` Office 365 SMTP
+* :gitlab-issue:`532` Workflow preview isn't updated right after transitions are modified
 * :gitlab-issue:`539` Setting for default email sender is missing
 
 

mayan/apps/document_states/api_views.py

@@ -2,6 +2,7 @@ from __future__ import absolute_import, unicode_literals
 
 from django.http import HttpResponse
 from django.shortcuts import get_object_or_404
+from django.views.decorators.cache import cache_control, patch_cache_control
 
 from rest_framework import generics
 
@@ -24,6 +25,7 @@ from .serializers import (
     WritableWorkflowInstanceLogEntrySerializer, WritableWorkflowSerializer,
     WritableWorkflowTransitionSerializer
 )
+from .settings import settings_workflow_image_cache_time
 from .storages import storage_workflowimagecache
 from .tasks import task_generate_workflow_image
 
@@ -243,6 +245,7 @@ class APIWorkflowImageView(generics.RetrieveAPIView):
     def get_serializer_class(self):
         return None
 
+    @cache_control(private=True)
     def retrieve(self, request, *args, **kwargs):
         task = task_generate_workflow_image.apply_async(
             kwargs=dict(
@@ -253,6 +256,11 @@ class APIWorkflowImageView(generics.RetrieveAPIView):
         cache_filename = task.get(timeout=WORKFLOW_IMAGE_TASK_TIMEOUT)
         with storage_workflowimagecache.open(cache_filename) as file_object:
             response = HttpResponse(file_object.read(), content_type='image')
+            if '_hash' in request.GET:
+                patch_cache_control(
+                    response,
+                    max_age=settings_workflow_image_cache_time.value
+                )
             return response
 
 

mayan/apps/document_states/fields.py

@@ -0,0 +1,9 @@
+from __future__ import absolute_import, unicode_literals
+
+from django import forms
+
+from .widgets import WorkflowImageWidget
+
+
+class WorfklowImageField(forms.fields.Field):
+    widget = WorkflowImageWidget

mayan/apps/document_states/forms.py

@@ -12,10 +12,10 @@ from django.utils.translation import ugettext_lazy as _
 from common.forms import DynamicModelForm
 
 from .classes import WorkflowAction
+from .fields import WorfklowImageField
 from .models import (
     Workflow, WorkflowState, WorkflowStateAction, WorkflowTransition
 )
-from .widgets import WorkflowImageWidget
 
 
 class WorkflowActionSelectionForm(forms.Form):
@@ -178,9 +178,9 @@ class WorkflowInstanceTransitionForm(forms.Form):
 
 
 class WorkflowPreviewForm(forms.Form):
-    preview = forms.IntegerField(widget=WorkflowImageWidget())
+    workflow = WorfklowImageField()
 
     def __init__(self, *args, **kwargs):
         instance = kwargs.pop('instance', None)
         super(WorkflowPreviewForm, self).__init__(*args, **kwargs)
-        self.fields['preview'].initial = instance
+        self.fields['workflow'].initial = instance

mayan/apps/document_states/models.py

@@ -1,11 +1,14 @@
 from __future__ import absolute_import, unicode_literals
 
+import hashlib
 import json
 import logging
 
+from furl import furl
 from graphviz import Digraph
 
 from django.conf import settings
+from django.core import serializers
 from django.core.files.base import ContentFile
 from django.core.exceptions import PermissionDenied, ValidationError
 from django.db import IntegrityError, models
@@ -65,7 +68,7 @@ class Workflow(models.Model):
         return self.label
 
     def generate_image(self):
-        cache_filename = '{}'.format(self.id)
+        cache_filename = '{}-{}'.format(self.id, self.get_hash())
         image = self.render()
 
         # Since open "wb+" doesn't create files, check if the file
@@ -80,9 +83,30 @@ class Workflow(models.Model):
 
         return cache_filename
 
+    def get_api_image_url(self, *args, **kwargs):
+        final_url = furl()
+        final_url.args = kwargs
+        final_url.path = reverse('rest_api:workflow-image', args=(self.pk,))
+        final_url.args['_hash'] = self.get_hash()
+
+        return final_url.tostr()
+
     def get_document_types_not_in_workflow(self):
         return DocumentType.objects.exclude(pk__in=self.document_types.all())
 
+    def get_hash(self):
+        objects_lists = list(
+            Workflow.objects.filter(pk=self.pk)
+        ) + list(
+            WorkflowState.objects.filter(workflow__pk=self.pk)
+        ) + list(
+            WorkflowTransition.objects.filter(workflow__pk=self.pk)
+        )
+
+        return hashlib.sha256(
+            serializers.serialize('json', objects_lists)
+        ).hexdigest()
+
     def get_initial_state(self):
         try:
             return self.states.get(initial=True)

mayan/apps/document_states/settings.py

@@ -9,6 +9,13 @@ from smart_settings import Namespace
 
 namespace = Namespace(name='document_states', label=_('Workflows'))
 
+settings_workflow_image_cache_time = namespace.add_setting(
+    global_name='WORKFLOWS_IMAGE_CACHE_TIME', default='31556926',
+    help_text=_(
+        'Time in seconds that the browser should cache the supplied workflow '
+        'images. The default of 31559626 seconds corresponde to 1 year.'
+    )
+)
 setting_workflowimagecache_storage = namespace.add_setting(
     global_name='WORKFLOWS_IMAGE_CACHE_STORAGE_BACKEND',
     default='django.core.files.storage.FileSystemStorage', help_text=_(

mayan/apps/document_states/templates/document_states/forms/widgets/workflow_image.html

@@ -1 +1 @@
-<img class="img-responsive" name="{{ widget.name }}" {% include "django/forms/widgets/attrs.html" %} src="{% url 'rest_api:workflow-image' widget.value.pk %}" style="margin:auto;" />
+<img class="img-responsive" name="{{ widget.name }}" {% include "django/forms/widgets/attrs.html" %} src="{{ widget.value.get_api_image_url }}" style="margin:auto;" />

mayan/apps/document_states/urls.py

@@ -23,8 +23,8 @@ from .views import (
     SetupWorkflowTransitionEditView,
     SetupWorkflowTransitionTriggerEventListView, ToolLaunchAllWorkflows,
     WorkflowDocumentListView, WorkflowInstanceDetailView,
-    WorkflowImageView, WorkflowInstanceTransitionView, WorkflowListView,
-    WorkflowPreviewView, WorkflowStateDocumentListView, WorkflowStateListView,
+    WorkflowInstanceTransitionView, WorkflowListView, WorkflowPreviewView,
+    WorkflowStateDocumentListView, WorkflowStateListView,
 )
 
 urlpatterns = [
@@ -166,11 +166,6 @@ urlpatterns = [
         WorkflowStateListView.as_view(),
         name='workflow_state_list'
     ),
-    url(
-        r'^(?P<pk>\d+)/image/$',
-        WorkflowImageView.as_view(),
-        name='workflow_image'
-    ),
     url(
         r'^(?P<pk>\d+)/preview/$',
         WorkflowPreviewView.as_view(),

mayan/apps/document_states/views.py

@@ -1,7 +1,6 @@
 from __future__ import absolute_import, unicode_literals
 
 from django.contrib import messages
-from django.core.files.base import ContentFile
 from django.db import transaction
 from django.db.utils import IntegrityError
 from django.http import Http404, HttpResponseRedirect
@@ -15,7 +14,7 @@ from common.views import (
     AssignRemoveView, ConfirmView, FormView, SingleObjectCreateView,
     SingleObjectDeleteView, SingleObjectDetailView,
     SingleObjectDynamicFormCreateView, SingleObjectDynamicFormEditView,
-    SingleObjectDownloadView, SingleObjectEditView, SingleObjectListView
+    SingleObjectEditView, SingleObjectListView
 )
 from documents.models import Document
 from documents.views import DocumentListView
@@ -907,19 +906,6 @@ class ToolLaunchAllWorkflows(ConfirmView):
         )
 
 
-class WorkflowImageView(SingleObjectDownloadView):
-    attachment = False
-    model = Workflow
-    object_permission = permission_workflow_view
-
-    def get_file(self):
-        workflow = self.get_object()
-        return ContentFile(workflow.render(), name=workflow.label)
-
-    def get_mimetype(self):
-        return 'image'
-
-
 class WorkflowPreviewView(SingleObjectDetailView):
     form_class = WorkflowPreviewForm
     model = Workflow
@@ -928,5 +914,6 @@ class WorkflowPreviewView(SingleObjectDetailView):
     def get_extra_context(self):
         return {
             'hide_labels': True,
+            'object': self.get_object(),
             'title': _('Preview of: %s') % self.get_object()
         }