fix a bug that breaks job cancel on single node jobs

1.  Install awx w/ a single node.
2.  Start a long-running job.
3.  Forcibly kill the `awx-manage run_dispatcher` process (e.g.,
    SIGKILL) and do not start it again.
4.  The job remains in running - without a second cluster to discover
    the job, it is never reaped.
5.  This PR allows you to cancel the job from the UI+API.

awx/main/dispatch/control.py

@@ -14,18 +14,18 @@ class Control(object):
     services = ('dispatcher', 'callback_receiver')
     result = None
 
-    def __init__(self, service):
+    def __init__(self, service, host=None):
         if service not in self.services:
             raise RuntimeError('{} must be in {}'.format(service, self.services))
         self.service = service
-        queuename = get_local_queuename()
-        self.queue = Queue(queuename, Exchange(queuename), routing_key=queuename)
+        self.queuename = host or get_local_queuename()
+        self.queue = Queue(self.queuename, Exchange(self.queuename), routing_key=self.queuename)
 
-    def publish(self, msg, conn, host, **kwargs):
+    def publish(self, msg, conn, **kwargs):
         producer = Producer(
             exchange=self.queue.exchange,
             channel=conn,
-            routing_key=get_local_queuename()
+            routing_key=self.queuename
         )
         producer.publish(msg, expiration=5, **kwargs)
 
@@ -35,14 +35,13 @@ class Control(object):
     def running(self, *args, **kwargs):
         return self.control_with_reply('running', *args, **kwargs)
 
-    def control_with_reply(self, command, host=None, timeout=5):
-        host = host or settings.CLUSTER_HOST_ID
-        logger.warn('checking {} {} for {}'.format(self.service, command, host))
+    def control_with_reply(self, command, timeout=5):
+        logger.warn('checking {} {} for {}'.format(self.service, command, self.queuename))
         reply_queue = Queue(name="amq.rabbitmq.reply-to")
         self.result = None
         with Connection(settings.BROKER_URL) as conn:
             with Consumer(conn, reply_queue, callbacks=[self.process_message], no_ack=True):
-                self.publish({'control': command}, conn, host, reply_to='amq.rabbitmq.reply-to')
+                self.publish({'control': command}, conn, reply_to='amq.rabbitmq.reply-to')
                 try:
                     conn.drain_events(timeout=timeout)
                 except socket.timeout:
@@ -50,10 +49,9 @@ class Control(object):
                     raise
         return self.result
 
-    def control(self, msg, host=None, **kwargs):
-        host = host or settings.CLUSTER_HOST_ID
+    def control(self, msg, **kwargs):
         with Connection(settings.BROKER_URL) as conn:
-            self.publish(msg, conn, host)
+            self.publish(msg, conn)
 
     def process_message(self, body, message):
         self.result = body

awx/main/models/unified_jobs.py

@@ -7,9 +7,11 @@ import json
 import logging
 import os
 import re
+import socket
 import subprocess
 import tempfile
 from collections import OrderedDict
+import six
 
 # Django
 from django.conf import settings
@@ -29,6 +31,7 @@ from polymorphic.models import PolymorphicModel
 
 # AWX
 from awx.main.models.base import * # noqa
+from awx.main.dispatch.control import Control as ControlDispatcher
 from awx.main.models.mixins import ResourceMixin, TaskManagerUnifiedJobMixin
 from awx.main.utils import (
     encrypt_dict, decrypt_field, _inventory_updates,
@@ -1248,6 +1251,31 @@ class UnifiedJob(PolymorphicModel, PasswordFieldsModel, CommonModelNameNotUnique
         # Done!
         return True
 
+
+    @property
+    def actually_running(self):
+        # returns True if the job is running in the appropriate dispatcher process
+        running = False
+        if all([
+            self.status == 'running',
+            self.celery_task_id,
+            self.execution_node
+        ]):
+            # If the job is marked as running, but the dispatcher
+            # doesn't know about it (or the dispatcher doesn't reply),
+            # then cancel the job
+            timeout = 5
+            try:
+                running = self.celery_task_id in ControlDispatcher(
+                    'dispatcher', self.execution_node
+                ).running(timeout=timeout)
+            except socket.timeout:
+                logger.error(six.text_type(
+                    'could not reach dispatcher on {} within {}s'
+                ).format(self.execution_node, timeout))
+                running = False
+        return running
+
     @property
     def can_cancel(self):
         return bool(self.status in CAN_CANCEL)
@@ -1270,6 +1298,9 @@ class UnifiedJob(PolymorphicModel, PasswordFieldsModel, CommonModelNameNotUnique
                 if self.status in ('pending', 'waiting', 'new'):
                     self.status = 'canceled'
                     cancel_fields.append('status')
+                if self.status == 'running' and not self.actually_running:
+                    self.status = 'canceled'
+                    cancel_fields.append('status')
                 if job_explanation is not None:
                     self.job_explanation = job_explanation
                     cancel_fields.append('job_explanation')

awx/main/models/workflow.py

@@ -481,3 +481,9 @@ class WorkflowJob(UnifiedJob, WorkflowJobOptions, SurveyJobMixin, JobNotificatio
     @property
     def preferred_instance_groups(self):
         return []
+
+    @property
+    def actually_running(self):
+        # WorkflowJobs don't _actually_ run anything in the dispatcher, so
+        # there's no point in asking the dispatcher if it knows about this task
+        return self.status == 'running'