Paginate the job_tasks page.

This commit adds pagination to the /api/v1/jobs/{id}/job_tasks/ page,
which previously lacked it.

AC-1340

awx/api/utils/decorators.py

@@ -0,0 +1,66 @@
+# Copyright (c) 2014 Ansible, Inc.
+# All Rights Reserved.
+
+import collections
+import copy
+import functools
+
+from rest_framework.response import Response
+from rest_framework.settings import api_settings
+
+def paginated(method):
+    """Given an method with a Django REST Framework API method signature
+    (e.g. `def get(self, request, ...):`), abstract out boilerplate pagination
+    duties.
+
+    This causes the method to receive two additional keyword arguments:
+    `limit`, and `offset`. The method expects a two-tuple to be
+    returned, with a result list as the first item, and the total number
+    of results (across all pages) as the second item.
+    """
+    @functools.wraps(method)
+    def func(self, request, *args, **kwargs):
+        # Manually spin up pagination.
+        # How many results do we show?
+        limit = api_settings.PAGINATE_BY
+        if request.QUERY_PARAMS.get(api_settings.PAGINATE_BY_PARAM, False):
+            limit = request.QUERY_PARAMS[api_settings.PAGINATE_BY_PARAM]
+        if api_settings.MAX_PAGINATE_BY:
+            limit = min(api_settings.MAX_PAGINATE_BY, limit)
+        limit = int(limit)
+
+        # What page are we on?
+        page = int(request.QUERY_PARAMS.get('page', 1))
+        offset = (page - 1) * limit
+
+        # Add the limit, offset, and page variables to the keyword arguments
+        # being sent to the underlying method.
+        kwargs['limit'] = limit
+        kwargs['offset'] = offset
+
+        # Okay, call the underlying method.
+        results, count = method(self, request, *args, **kwargs)
+
+        # Determine the next and previous pages, if any.
+        prev, next_ = None, None
+        if page > 1:
+            get_copy = copy.copy(request.GET)
+            get_copy['page'] = page - 1
+            prev = '%s?%s' % (request.path, get_copy.urlencode())
+        if count > offset + limit:
+            get_copy = copy.copy(request.GET)
+            get_copy['page'] = page + 1
+            next_ = '%s?%s' % (request.path, get_copy.urlencode())
+
+        # Compile the results into a dictionary with pagination
+        # information.
+        answer = collections.OrderedDict((
+            ('count', count),
+            ('next', next_),
+            ('previous', prev),
+            ('results', results),
+        ))
+
+        # Okay, we're done; return response data.
+        return Response(answer)
+    return func

awx/api/views.py

@@ -21,6 +21,7 @@ from django.utils.timezone import now
 # Django REST Framework
 from rest_framework.authtoken.views import ObtainAuthToken
 from rest_framework.exceptions import PermissionDenied, ParseError
+from rest_framework.pagination import BasePaginationSerializer
 from rest_framework.parsers import YAMLParser
 from rest_framework.permissions import AllowAny, IsAuthenticated
 from rest_framework.renderers import YAMLRenderer
@@ -42,6 +43,7 @@ from awx.api.authentication import JobTaskAuthentication
 from awx.api.permissions import *
 from awx.api.renderers import *
 from awx.api.serializers import *
+from awx.api.utils.decorators import paginated
 from awx.api.generics import *
 from awx.api.generics import get_view_name
 
@@ -1517,25 +1519,85 @@ class JobJobPlaysList(BaseJobEventsList):
             all_plays.append(play_details)
         return Response(all_plays)
 
-class JobJobTasksList(BaseJobEventsList):
 
+class JobJobTasksList(BaseJobEventsList):
+    """A view for displaying aggregate data about tasks within a job
+    and their completion status.
+    """
     parent_model = Job
     authentication_classes = [JobTaskAuthentication] + \
                              api_settings.DEFAULT_AUTHENTICATION_CLASSES
     permission_classes = (JobTaskPermission,)
     new_in_150 = True
 
-    def get(self, request, *args, **kwargs):
+    @paginated
-        tasks = []
+    def get(self, request, limit, offset, *args, **kwargs):
+        """Return aggregate data about each of the job tasks that is:
+          - an immediate child of the job event
+          - corresponding to the spinning up of a new task or playbook
+        """
+        results = []
+
+        # Get the job and the parent task.
+        # If there's no event ID specified, this will return a 404.
+        # FIXME: Make this a good error message.
         job = get_object_or_404(self.parent_model, pk=self.kwargs['pk'])
-        parent_task = get_object_or_404(job.job_events, pk=int(request.QUERY_PARAMS.get('event_id', -1)))
+        parent_task = get_object_or_404(job.job_events,
-        for task_start_event in parent_task.children.filter(Q(event='playbook_on_task_start') | Q(event='playbook_on_setup')):
+            pk=int(request.QUERY_PARAMS.get('event_id', -1)),
-            task_data = dict(id=task_start_event.id, name="Gathering Facts" if task_start_event.event == 'playbook_on_setup' else task_start_event.task,
+        )
-                             created=task_start_event.created, modified=task_start_event.modified,
+
-                             failed=False, changed=False, host_count=0, reported_hosts=0, successful_count=0, failed_count=0,
+        # Some events correspond to a playbook or task starting up,
-                             changed_count=0, skipped_count=0)
+        # and these are what we're interested in here.
-            for child_event in task_start_event.children.all():
+        STARTING_EVENTS = ('playbook_on_task_start', 'playbook_on_setup')
-                if child_event.event == 'runner_on_failed':
+
+        # We need to pull information about each start event.
+        #
+        # This is super tricky, because this table has a one-to-many
+        # relationship with itself (parent-child), and we're getting
+        # information for an arbitrary number of children. This means we
+        # need stats on grandchildren, sorted by child. 
+        queryset = (JobEvent.objects.filter(parent__parent=parent_task,
+                                            parent__event__in=STARTING_EVENTS)
+                                    .values('parent__id', 'event', 'changed')
+                                    .annotate(num=Count('event'))
+                                    .order_by('parent__id'))
+        count = queryset.count()
+
+        # The data above will come back in a list, but we are going to
+        # want to access it based on the parent id, so map it into a
+        # dictionary.
+        data = {}
+        for line in queryset[offset:offset + limit]:
+            parent_id = line.pop('parent__id')
+            data.setdefault(parent_id, [])
+            data[parent_id].append(line)
+
+        # Iterate over the start events and compile information about each one.
+        qs = parent_task.children.filter(event__in=STARTING_EVENTS,
+                                         id__in=data.keys())
+        for task_start_event in qs:
+            # Create initial task data.
+            task_data = {
+                'changed': False,
+                'changed_count': 0,
+                'created': task_start_event.created,
+                'failed': False,
+                'failed_count': 0,
+                'host_count': 0,
+                'id': task_start_event.id,
+                'modified': task_start_event.modified,
+                'name': 'Gathering Facts' if
+                            task_start_event.event == 'playbook_on_setup' else
+                            task_start_event.task,
+                'reported_hosts': 0,
+                'skipped_count': 0,
+                'successful_count': 0,
+            }
+
+            # Iterate over the data compiled for this child event, and
+            # make appropriate changes to the task data.
+            for child_data in data.get(task_start_event.id, []):
+                if child_data['event'] == 'runner_on_failed':
                     task_data['failed'] = True
                     task_data['host_count'] += 1
                     task_data['reported_hosts'] += 1
@@ -1556,11 +1618,14 @@ class JobJobTasksList(BaseJobEventsList):
                     task_data['host_count'] += 1
                     task_data['reported_hosts'] += 1
                     task_data['failed'] = True
-                    task_data['failed_count'] += 1
+                    task_data['failed_count'] += child_data['num']
-                elif child_event.event == 'runner_on_no_hosts':
+                elif child_data['event'] == 'runner_on_no_hosts':
-                    task_data['host_count'] += 1
+                    task_data['host_count'] += child_data['num']
-            tasks.append(task_data)
+            results.append(task_data)
-        return Response(tasks)
+
+        # Done; return the results and count.
+        return results, count
+
 
 class UnifiedJobTemplateList(ListAPIView):