Bug 1276216: make any tasks without dependencies depend on the decision task; r=ahal

MozReview-Commit-ID: 5k5jC7CCHNW

--HG--
extra : rebase_source : 0f77e208b1947b2082481b7ceeab57055c13797e

taskcluster/taskgraph/create.py

@@ -7,6 +7,7 @@ from __future__ import absolute_import, print_function, unicode_literals
 import requests
 import json
 import collections
+import os
 import logging
 
 from slugid import nice as slugid
@@ -20,8 +21,17 @@ def create_tasks(taskgraph, label_to_taskid):
 
     session = requests.Session()
 
+    decision_task_id = os.environ.get('TASK_ID')
+
     for task_id in taskgraph.graph.visit_postorder():
         task_def = taskgraph.tasks[task_id].task
+
+        # if this task has no dependencies, make it depend on this decision
+        # task so that it does not start immediately; and so that if this loop
+        # fails halfway through, none of the already-created tasks run.
+        if decision_task_id and not task_def.get('dependencies'):
+            task_def['dependencies'] = [decision_task_id]
+
         task_def['taskGroupId'] = task_group_id
         _create_task(session, task_id, taskid_to_label[task_id], task_def)
 

taskcluster/taskgraph/test/test_create.py

@@ -5,6 +5,7 @@
 from __future__ import absolute_import, print_function, unicode_literals
 
 import unittest
+import os
 
 from .. import create
 from ..graph import Graph
@@ -24,12 +25,19 @@ class FakeKind(object):
 class TestCreate(unittest.TestCase):
 
     def setUp(self):
+        self.old_task_id = os.environ.get('TASK_ID')
+        if 'TASK_ID' in os.environ:
+            del os.environ['TASK_ID']
         self.created_tasks = {}
         self.old_create_task = create._create_task
         create._create_task = self.fake_create_task
 
     def tearDown(self):
         create._create_task = self.old_create_task
+        if self.old_task_id:
+            os.environ['TASK_ID'] = self.old_task_id
+        elif 'TASK_ID' in os.environ:
+            del os.environ['TASK_ID']
 
     def fake_create_task(self, session, task_id, label, task_def):
         self.created_tasks[task_id] = task_def
@@ -52,6 +60,22 @@ class TestCreate(unittest.TestCase):
             for depid in task.get('dependencies', []):
                 self.assertIn(depid, self.created_tasks)
 
+    def test_create_task_without_dependencies(self):
+        "a task with no dependencies depends on the decision task"
+        os.environ['TASK_ID'] = 'decisiontask'
+        kind = FakeKind()
+        tasks = {
+            'tid-a': Task(kind=kind, label='a', task={'payload': 'hello world'}),
+        }
+        label_to_taskid = {'a': 'tid-a'}
+        graph = Graph(nodes={'tid-a'}, edges=set())
+        taskgraph = TaskGraph(tasks, graph)
+
+        create.create_tasks(taskgraph, label_to_taskid)
+
+        for tid, task in self.created_tasks.iteritems():
+            self.assertEqual(task['dependencies'], [os.environ['TASK_ID']])
+
 
 if __name__ == '__main__':
     main()