Delete jobs without loading objects first

The commit is intended to speed up the cleanup_jobs command in awx. Old
methods takes 7+ hours to delete 1 million old jobs. New method takes
around 6 minutes.

Leverages a sub-classed Collector, called AWXCollector, that does not
load in objects before deleting them. Instead querysets, which are
lazily evaluated, are used in places where Collector normally keeps a
list of objects.

Finally, a couple of tests to ensure parity between old Collector and
AWXCollector. That is, any object that is updated/removed from the
database using Collector should be have identical operations using
AWXCollector.

tower issue 1103

awx/main/tests/functional/commands/test_cleanup_jobs.py

@@ -0,0 +1,179 @@
+import pytest
+from datetime import datetime, timedelta
+from pytz import timezone
+from collections import OrderedDict
+
+from django.db.models.deletion import Collector, SET_NULL, CASCADE
+from django.core.management import call_command
+
+from awx.main.management.commands.deletion import AWXCollector
+from awx.main.models import (
+    JobTemplate, User, Job, JobEvent, Notification,
+    WorkflowJobNode, JobHostSummary
+)
+
+
+@pytest.fixture
+def setup_environment(inventory, project, machine_credential, host, notification_template, label):
+    '''
+    Create old jobs and new jobs, with various other objects to hit the
+    related fields of Jobs. This makes sure on_delete() effects are tested
+    properly.
+    '''
+    old_jobs = []
+    new_jobs = []
+    days = 10
+    days_str = str(days)
+
+    jt = JobTemplate.objects.create(name='testjt', inventory=inventory, project=project)
+    jt.credentials.add(machine_credential)
+    jt_user = User.objects.create(username='jobtemplateuser')
+    jt.execute_role.members.add(jt_user)
+
+    notification = Notification()
+    notification.notification_template = notification_template
+    notification.save()
+
+    for i in range(3):
+        job1 = jt.create_job()
+        job1.created =datetime.now(tz=timezone('UTC'))
+        job1.save()
+        # create jobs with current time
+        JobEvent.create_from_data(job_id=job1.pk, uuid='abc123', event='runner_on_start',
+                                  stdout='a' * 1025).save()
+        new_jobs.append(job1)
+
+        job2 = jt.create_job()
+        # create jobs 10 days ago
+        job2.created = datetime.now(tz=timezone('UTC')) - timedelta(days=days)
+        job2.save()
+        job2.dependent_jobs.add(job1)
+        JobEvent.create_from_data(job_id=job2.pk, uuid='abc123', event='runner_on_start',
+                                  stdout='a' * 1025).save()
+        old_jobs.append(job2)
+
+    jt.last_job = job2
+    jt.current_job = job2
+    jt.save()
+    host.last_job = job2
+    host.save()
+    notification.unifiedjob_notifications.add(job2)
+    label.unifiedjob_labels.add(job2)
+    jn = WorkflowJobNode.objects.create(job=job2)
+    jn.save()
+    jh = JobHostSummary.objects.create(job=job2)
+    jh.save()
+
+    return (old_jobs, new_jobs, days_str)
+
+
+@pytest.mark.django_db
+def test_cleanup_jobs(setup_environment):
+    (old_jobs, new_jobs, days_str) = setup_environment
+
+    # related_fields
+    related = [f for f in Job._meta.get_fields(include_hidden=True)
+               if f.auto_created and not
+               f.concrete and
+               (f.one_to_one or f.one_to_many)]
+
+    job = old_jobs[-1] # last job
+
+    # gather related objects for job
+    related_should_be_removed = {}
+    related_should_be_null = {}
+    for r in related:
+        qs = r.related_model._base_manager.using('default').filter(
+            **{"%s__in" % r.field.name: [job.pk]}
+        )
+        if qs.exists():
+            if r.field.remote_field.on_delete == CASCADE:
+                related_should_be_removed[qs.model] = set(qs.values_list('pk', flat=True))
+            if r.field.remote_field.on_delete == SET_NULL:
+                related_should_be_null[(qs.model,r.field.name)] = set(qs.values_list('pk', flat=True))
+
+    assert related_should_be_removed
+    assert related_should_be_null
+
+    call_command('cleanup_jobs', '--days', days_str)
+    # make sure old jobs are removed
+    assert not Job.objects.filter(pk__in=[obj.pk for obj in old_jobs]).exists()
+
+    # make sure new jobs are untouched
+    assert len(new_jobs) == Job.objects.filter(pk__in=[obj.pk for obj in new_jobs]).count()
+
+    # make sure related objects are destroyed or set to NULL (none)
+    for model, values in related_should_be_removed.items():
+        assert not model.objects.filter(pk__in=values).exists()
+
+    for (model,fieldname), values in related_should_be_null.items():
+        for v in values:
+            assert not getattr(model.objects.get(pk=v), fieldname)
+
+
+@pytest.mark.django_db
+def test_awxcollector(setup_environment):
+    '''
+    Efforts to improve the performance of cleanup_jobs involved
+    sub-classing the django Collector class. This unit test will
+    check for parity between the django Collector and the modified
+    AWXCollector class. AWXCollector is used in cleanup_jobs to
+    bulk-delete old jobs from the database.
+
+    Specifically, Collector has four dictionaries to check:
+    .dependencies, .data, .fast_deletes, and .field_updates
+
+    These tests will convert each dictionary from AWXCollector
+    (after running .collect on jobs), from querysets to sets of
+    objects. The final result should be a dictionary that is
+    equivalent to django's Collector.
+    '''
+
+    (old_jobs, new_jobs, days_str) = setup_environment
+    collector = Collector('default')
+    collector.collect(old_jobs)
+
+    awx_col = AWXCollector('default')
+    # awx_col accepts a queryset as input
+    awx_col.collect(Job.objects.filter(pk__in=[obj.pk for obj in old_jobs]))
+
+    # check that dependencies are the same
+    assert awx_col.dependencies == collector.dependencies
+
+    # check that objects to delete are the same
+    awx_del_dict = OrderedDict()
+    for model, instances in awx_col.data.items():
+        awx_del_dict.setdefault(model, set())
+        for inst in instances:
+            # .update() will put each object in a queryset into the set
+            awx_del_dict[model].update(inst)
+    assert awx_del_dict == collector.data
+
+    # check that field updates are the same
+    awx_del_dict = OrderedDict()
+    for model, instances_for_fieldvalues in awx_col.field_updates.items():
+        awx_del_dict.setdefault(model, {})
+        for (field, value), instances in instances_for_fieldvalues.items():
+            awx_del_dict[model].setdefault((field,value), set())
+            for inst in instances:
+                awx_del_dict[model][(field,value)].update(inst)
+
+    # collector field updates don't use the base (polymorphic parent) model, e.g.
+    # it will use JobTemplate instead of UnifiedJobTemplate. Therefore,
+    # we need to rebuild the dictionary and grab the model from the field
+    collector_del_dict = OrderedDict()
+    for model, instances_for_fieldvalues in collector.field_updates.items():
+        for (field,value), instances in instances_for_fieldvalues.items():
+            collector_del_dict.setdefault(field.model, {})
+            collector_del_dict[field.model][(field, value)] = collector.field_updates[model][(field,value)]
+    assert awx_del_dict == collector_del_dict
+
+    # check that fast deletes are the same
+    collector_fast_deletes = set()
+    for q in collector.fast_deletes:
+        collector_fast_deletes.update(q)
+
+    awx_col_fast_deletes = set()
+    for q in awx_col.fast_deletes:
+        awx_col_fast_deletes.update(q)
+    assert collector_fast_deletes == awx_col_fast_deletes