don't access the database in our custom route_for_task

If database connectivity is lost/interrupted in this block of celery
internals, beat is *not* smart enough to recover, and it gets stuck in
an endless fail loop.  We don't _need_ to talk to the database here
anyways; just use settings.CLUSTER_HOST_ID to get what we need.

see: https://github.com/ansible/tower/issues/2957

awx/main/tests/unit/utils/test_ha.py

@@ -1,68 +0,0 @@
-# -*- coding: utf-8 -*-
-
-# Copyright (c) 2017 Ansible Tower by Red Hat
-# All Rights Reserved.
-
-# python
-import pytest
-import mock
-
-# AWX
-from awx.main.utils.ha import (
-    AWXCeleryRouter,
-)
-
-
-class TestAddRemoveCeleryWorkerQueues():
-    @pytest.fixture
-    def instance_generator(self, mocker):
-        def fn(hostname='east-1'):
-            groups=['east', 'west', 'north', 'south']
-            instance = mocker.MagicMock()
-            instance.hostname = hostname
-            instance.rampart_groups = mocker.MagicMock()
-            instance.rampart_groups.values_list = mocker.MagicMock(return_value=groups)
-
-            return instance
-        return fn
-
-    @pytest.fixture
-    def worker_queues_generator(self, mocker):
-        def fn(queues=['east', 'west']):
-            return [dict(name=n, alias='') for n in queues]
-        return fn
-
-    @pytest.fixture
-    def mock_app(self, mocker):
-        app = mocker.MagicMock()
-        app.control = mocker.MagicMock()
-        app.control.cancel_consumer = mocker.MagicMock()
-        return app
-
-
-class TestUpdateCeleryWorkerRouter():
-
-    @pytest.mark.parametrize("is_controller,expected_routes", [
-        (False, {
-            'awx.main.tasks.cluster_node_heartbeat': {'queue': 'east-1', 'routing_key': 'east-1'},
-            'awx.main.tasks.purge_old_stdout_files': {'queue': 'east-1', 'routing_key': 'east-1'}
-        }),
-        (True, {
-            'awx.main.tasks.cluster_node_heartbeat': {'queue': 'east-1', 'routing_key': 'east-1'},
-            'awx.main.tasks.purge_old_stdout_files': {'queue': 'east-1', 'routing_key': 'east-1'},
-            'awx.main.tasks.awx_isolated_heartbeat': {'queue': 'east-1', 'routing_key': 'east-1'},
-        }),
-    ])
-    def test_update_celery_worker_routes(self, mocker, is_controller, expected_routes):
-        def get_or_register():
-            instance = mock.MagicMock()
-            instance.hostname = 'east-1'
-            instance.is_controller = mock.MagicMock(return_value=is_controller)
-            return (False, instance)
-
-        with mock.patch('awx.main.models.Instance.objects.get_or_register', get_or_register):
-            router = AWXCeleryRouter()
-
-            for k,v in expected_routes.iteritems():
-                assert router.route_for_task(k) == v
-

awx/main/utils/ha.py

@@ -3,21 +3,15 @@
 # Copyright (c) 2017 Ansible Tower by Red Hat
 # All Rights Reserved.
 
-from awx.main.models import Instance
+from django.conf import settings
 
 
 class AWXCeleryRouter(object):
     def route_for_task(self, task, args=None, kwargs=None):
-        (changed, instance) = Instance.objects.get_or_register()
         tasks = [
             'awx.main.tasks.cluster_node_heartbeat',
             'awx.main.tasks.purge_old_stdout_files',
-        ]
-        isolated_tasks = [
             'awx.main.tasks.awx_isolated_heartbeat',
         ]
         if task in tasks:
-            return {'queue': instance.hostname.encode("utf8"), 'routing_key': instance.hostname.encode("utf8")}
+            return {'queue': settings.CLUSTER_HOST_ID, 'routing_key': settings.CLUSTER_HOST_ID}
-
-        if instance.is_controller() and task in isolated_tasks:
-            return {'queue': instance.hostname.encode("utf8"), 'routing_key': instance.hostname.encode("utf8")}