fix slicing task_impact and script gen bugs

awx/main/models/inventory.py

@@ -247,6 +247,7 @@ class Inventory(CommonModelNameNotUnique, ResourceMixin, RelatedJobsMixin):
 
         data = dict()
         all_group = data.setdefault('all', dict())
+        all_hostnames = set(host.name for host in hosts)
 
         if self.variables_dict:
             all_group['vars'] = self.variables_dict
@@ -264,6 +265,8 @@ class Inventory(CommonModelNameNotUnique, ResourceMixin, RelatedJobsMixin):
             ).values_list('group_id', 'host_id', 'host__name')
             group_hosts_map = {}
             for group_id, host_id, host_name in group_hosts_qs:
+                if host_name not in all_hostnames:
+                    continue  # host might not be in current shard
                 group_hostnames = group_hosts_map.setdefault(group_id, [])
                 group_hostnames.append(host_name)
                 grouped_hosts.add(host_name)

awx/main/models/jobs.py

@@ -595,6 +595,7 @@ class Job(UnifiedJob, JobOptions, SurveyJobMixin, JobNotificationMixin, TaskMana
         new_prompts['_prevent_slicing'] = True
         new_prompts.setdefault('_eager_fields', {})
         new_prompts['_eager_fields']['job_slice_number'] = self.job_slice_number
+        new_prompts['_eager_fields']['job_slice_count'] = self.job_slice_count
         return super(Job, self).copy_unified_job(**new_prompts)
 
     @property
@@ -690,6 +691,9 @@ class Job(UnifiedJob, JobOptions, SurveyJobMixin, JobNotificationMixin, TaskMana
             count_hosts = 2
         else:
             count_hosts = Host.objects.filter(inventory__jobs__pk=self.pk).count()
+            if self.job_slice_count > 1:
+                # Integer division intentional
+                count_hosts = (count_hosts + self.job_slice_count - self.job_slice_number) / self.job_slice_count
         return min(count_hosts, 5 if self.forks == 0 else self.forks) + 1
 
     @property