Map pipeline precedence to nodepool node priority

We set precedence in our pipeline configs but we do not pass it through
to the nodepool NodeRequest priority, which means that check can starve
gate.

Change-Id: Id3fa6f9ad6bdf23bf3af43c48289c4b918ea04f1

tests/fixtures/config/single-tenant/git/common-config/zuul.yaml

@@ -39,6 +39,7 @@
       gerrit:
         - event: ref-updated
           ref: ^(?!refs/).*$
+    precedence: low
 
 - job:
     name: base

tests/unit/test_scheduler.py

@@ -4613,6 +4613,45 @@ For CI problems and help debugging, contact ci@example.org"""
         self.assertIn('project-test1 : SKIPPED', A.messages[1])
         self.assertIn('project-test2 : SKIPPED', A.messages[1])
 
+    def test_nodepool_priority(self):
+        "Test that nodes are requested at the correct priority"
+
+        self.fake_nodepool.paused = True
+
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        self.fake_gerrit.addEvent(A.getRefUpdatedEvent())
+
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+
+        C = self.fake_gerrit.addFakeChange('org/project', 'master', 'C')
+        C.addApproval('Code-Review', 2)
+        self.fake_gerrit.addEvent(C.addApproval('Approved', 1))
+
+        self.waitUntilSettled()
+
+        reqs = self.fake_nodepool.getNodeRequests()
+
+        # The requests come back sorted by oid. Since we have three requests
+        # for the three changes each with a different priority.
+        # Also they get a serial number based on order they were received
+        # so the number on the endof the oid should map to order submitted.
+
+        # * gate first - high priority - change C
+        self.assertEqual(reqs[0]['_oid'], '100-0000000002')
+        self.assertEqual(reqs[0]['node_types'], ['label1'])
+        # * check second - normal priority - change B
+        self.assertEqual(reqs[1]['_oid'], '200-0000000001')
+        self.assertEqual(reqs[1]['node_types'], ['label1'])
+        # * post third - low priority - change A
+        # additionally, the post job defined uses an ubuntu-xenial node,
+        # so we include that check just as an extra verification
+        self.assertEqual(reqs[2]['_oid'], '300-0000000000')
+        self.assertEqual(reqs[2]['node_types'], ['ubuntu-xenial'])
+
+        self.fake_nodepool.paused = False
+        self.waitUntilSettled()
+
     @simple_layout('layouts/multiple-templates.yaml')
     def test_multiple_project_templates(self):
         # Test that applying multiple project templates to a project

zuul/model.py

@@ -44,6 +44,12 @@ PRECEDENCE_MAP = {
     'high': PRECEDENCE_HIGH,
 }
 
+PRIORITY_MAP = {
+    PRECEDENCE_NORMAL: 200,
+    PRECEDENCE_LOW: 300,
+    PRECEDENCE_HIGH: 100,
+}
+
 # Request states
 STATE_REQUESTED = 'requested'
 STATE_PENDING = 'pending'
@@ -524,6 +530,10 @@ class NodeRequest(object):
         self.failed = False
         self.canceled = False
 
+    @property
+    def priority(self):
+        return PRIORITY_MAP[self.build_set.item.pipeline.precedence]
+
     @property
     def fulfilled(self):
         return (self._state == STATE_FULFILLED) and not self.failed

zuul/zk.py

@@ -147,12 +147,10 @@ class ZooKeeper(object):
             from ZooKeeper).  The watcher should return False when
             further updates are no longer necessary.
         '''
-        priority = 100  # TODO(jeblair): integrate into nodereq
-
         data = node_request.toDict()
         data['created_time'] = time.time()
 
-        path = '%s/%s-' % (self.REQUEST_ROOT, priority)
+        path = '%s/%s-' % (self.REQUEST_ROOT, node_request.priority)
         path = self.client.create(path, self._dictToStr(data),
                                   makepath=True,
                                   sequence=True, ephemeral=True)