Add a Zuul trigger

This adds the ability for a pipelite to have multiple triggers.

This also adds a "Zuul" trigger which is used to generate trigger
events based on internal actions Zuul has taken.

It supports two event types:

 * parent-change-enqueued: This can be used so that other pipelines
   can enqueue children of parents that are enqueued in a different
   pipeline.  Specifically, this lets OpenStack enqueue changes in
   check when their parents are enqueued in gate (which may be
   necessary because of our clean check rules).

   This could be used to replace the internal logic that enqueues
   children in dependent pipelines (moving that into explicit
   configuration instead).

   One can also imagine a future 'change-enqueued' event so that a
   pipeline could react directly to a change in another.

 * project-change-merged:  This can be used to trigger changes on all
   open changes for a project when a change is merged to that project.

   Specifically, this lets us perform light-weight merge checks on all
   open changes whenever a change is merged.

Change-Id: I2a67699dbed92a6b9c143a77795cb126f1f4dd57

14 files changed, 434 insertions, 8 deletions

diff --git a/doc/source/triggers.rst b/doc/source/triggers.rst
index c4485bf5d..dd650f2ff 100644
--- a/doc/source/triggers.rst
+++ b/doc/source/triggers.rst
@@ -4,8 +4,7 @@ Triggers
 ========
 
 The process of merging a change starts with proposing a change to be
-merged.  Primarily, Zuul supports Gerrit as a triggering system, as
-well as a facility for triggering jobs based on a timer.
+merged.  Primarily, Zuul supports Gerrit as a triggering system.
 Zuul's design is modular, so alternate triggering and reporting
 systems can be supported.
 
@@ -40,3 +39,8 @@ Timer
 
 A simple timer trigger is available as well.  It supports triggering
 jobs in a pipeline based on cron-style time instructions.
+
+Zuul
+----
+
+The Zuul trigger generates events based on internal actions in Zuul.
diff --git a/doc/source/zuul.rst b/doc/source/zuul.rst
index 1b9ce641f..4c3f6d3e0 100644
--- a/doc/source/zuul.rst
+++ b/doc/source/zuul.rst
@@ -372,7 +372,7 @@ explanation of each of the parameters::
     DependentPipelineManager, see: :doc:`gating`.
 
 **trigger**
-  Exactly one trigger source must be supplied for each pipeline.
+  At least one trigger source must be supplied for each pipeline.
   Triggers are not exclusive -- matching events may be placed in
   multiple pipelines, and they will behave independently in each of
   the pipelines they match.  You may select from the following:
@@ -458,6 +458,31 @@ explanation of each of the parameters::
     supported, not the symbolic names.  Example: ``0 0 * * *`` runs
     at midnight.
 
+  **zuul**
+    This trigger supplies events generated internally by Zuul.
+    Multiple events may be listed.
+
+    *event*
+    The event name.  Currently supported:
+
+      *project-change-merged* when Zuul merges a change to a project,
+      it generates this event for every open change in the project.
+
+      *parent-change-enqueued* when Zuul enqueues a change into any
+      pipeline, it generates this event for every child of that
+      change.
+
+    *pipeline*
+    Only available for ``parent-change-enqueued`` events.  This is the
+    name of the pipeline in which the parent change was enqueued.
+
+    *require-approval*
+    This may be used for any event.  It requires that a certain kind
+    of approval be present for the current patchset of the change (the
+    approval could be added by the event in question).  It follows the
+    same syntax as the "approval" pipeline requirement below.
+
+
 **require**
   If this section is present, it established pre-requisites for any
   kind of item entering the Pipeline.  Regardless of how the item is
diff --git a/tests/base.py b/tests/base.py
index a86de82d7..1b8294486 100755
--- a/tests/base.py
+++ b/tests/base.py
@@ -52,6 +52,7 @@ import zuul.reporter.gerrit
 import zuul.reporter.smtp
 import zuul.trigger.gerrit
 import zuul.trigger.timer
+import zuul.trigger.zuultrigger
 
 FIXTURE_DIR = os.path.join(os.path.dirname(__file__),
                            'fixtures')
@@ -401,6 +402,11 @@ class FakeGerrit(object):
             return change.query()
         return {}
 
+    def simpleQuery(self, query):
+        # This is currently only used to return all open changes for a
+        # project
+        return [change.query() for change in self.changes.values()]
+
     def startWatching(self, *args, **kw):
         pass
 
@@ -906,6 +912,8 @@ class ZuulTestCase(testtools.TestCase):
         self.sched.registerTrigger(self.gerrit)
         self.timer = zuul.trigger.timer.Timer(self.config, self.sched)
         self.sched.registerTrigger(self.timer)
+        self.zuultrigger = zuul.trigger.zuultrigger.ZuulTrigger(self.config, self.sched)
+        self.sched.registerTrigger(self.zuultrigger)
 
         self.sched.registerReporter(
             zuul.reporter.gerrit.Reporter(self.gerrit))
diff --git a/tests/fixtures/layout-zuultrigger-enqueued.yaml b/tests/fixtures/layout-zuultrigger-enqueued.yaml
new file mode 100644
index 000000000..8babd9e71
--- /dev/null
+++ b/tests/fixtures/layout-zuultrigger-enqueued.yaml
@@ -0,0 +1,53 @@
+pipelines:
+  - name: check
+    manager: IndependentPipelineManager
+    source: gerrit
+    require:
+      approval:
+        - verified: -1
+    trigger:
+      gerrit:
+        - event: patchset-created
+      zuul:
+        - event: parent-change-enqueued
+          pipeline: gate
+    success:
+      gerrit:
+        verified: 1
+    failure:
+      gerrit:
+        verified: -1
+
+  - name: gate
+    manager: DependentPipelineManager
+    failure-message: Build failed.  For information on how to proceed, see http://wiki.example.org/Test_Failures
+    source: gerrit
+    require:
+      approval:
+        - verified: 1
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - approved: 1
+      zuul:
+        - event: parent-change-enqueued
+          pipeline: gate
+    success:
+      gerrit:
+        verified: 2
+        submit: true
+    failure:
+      gerrit:
+        verified: -2
+    start:
+      gerrit:
+        verified: 0
+    precedence: high
+
+projects:
+  - name: org/project
+    check:
+      - project-check
+    gate:
+      - project-gate
diff --git a/tests/fixtures/layout-zuultrigger-merged.yaml b/tests/fixtures/layout-zuultrigger-merged.yaml
new file mode 100644
index 000000000..657700dfe
--- /dev/null
+++ b/tests/fixtures/layout-zuultrigger-merged.yaml
@@ -0,0 +1,53 @@
+pipelines:
+  - name: check
+    manager: IndependentPipelineManager
+    source: gerrit
+    trigger:
+      gerrit:
+        - event: patchset-created
+    success:
+      gerrit:
+        verified: 1
+    failure:
+      gerrit:
+        verified: -1
+
+  - name: gate
+    manager: DependentPipelineManager
+    failure-message: Build failed.  For information on how to proceed, see http://wiki.example.org/Test_Failures
+    source: gerrit
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - approved: 1
+    success:
+      gerrit:
+        verified: 2
+        submit: true
+    failure:
+      gerrit:
+        verified: -2
+    start:
+      gerrit:
+        verified: 0
+    precedence: high
+
+  - name: merge-check
+    manager: IndependentPipelineManager
+    source: gerrit
+    trigger:
+      zuul:
+        - event: project-change-merged
+    merge-failure:
+      gerrit:
+        verified: -1
+
+projects:
+  - name: org/project
+    check:
+      - project-check
+    gate:
+      - project-gate
+    merge-check:
+      - noop
diff --git a/tests/test_scheduler.py b/tests/test_scheduler.py
index fe6a584d1..d22a7cae0 100755
--- a/tests/test_scheduler.py
+++ b/tests/test_scheduler.py
@@ -1737,6 +1737,7 @@ class TestScheduler(ZuulTestCase):
         sched = zuul.scheduler.Scheduler()
         sched.registerTrigger(None, 'gerrit')
         sched.registerTrigger(None, 'timer')
+        sched.registerTrigger(None, 'zuul')
         sched.testConfig(self.config.get('zuul', 'layout_config'))
 
     def test_build_description(self):
diff --git a/tests/test_zuultrigger.py b/tests/test_zuultrigger.py
new file mode 100644
index 000000000..eb8fdc533
--- /dev/null
+++ b/tests/test_zuultrigger.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+
+# Copyright 2014 Hewlett-Packard Development Company, L.P.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import logging
+import time
+
+from tests.base import ZuulTestCase
+
+logging.basicConfig(level=logging.DEBUG,
+                    format='%(asctime)s %(name)-32s '
+                    '%(levelname)-8s %(message)s')
+
+
+class TestZuulTrigger(ZuulTestCase):
+    """Test Zuul Trigger"""
+
+    def test_zuul_trigger_parent_change_enqueued(self):
+        "Test Zuul trigger event: parent-change-enqueued"
+        self.config.set('zuul', 'layout_config',
+                        'tests/fixtures/layout-zuultrigger-enqueued.yaml')
+        self.sched.reconfigure(self.config)
+        self.registerJobs()
+
+        # This test has the following three changes:
+        # B1 -> A; B2 -> A
+        # When A is enqueued in the gate, B1 and B2 should both attempt
+        # to be enqueued in both pipelines.  B1 should end up in check
+        # and B2 in gate because of differing pipeline requirements.
+        self.worker.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        B1 = self.fake_gerrit.addFakeChange('org/project', 'master', 'B1')
+        B2 = self.fake_gerrit.addFakeChange('org/project', 'master', 'B2')
+        A.addApproval('CRVW', 2)
+        B1.addApproval('CRVW', 2)
+        B2.addApproval('CRVW', 2)
+        A.addApproval('VRFY', 1)  # required by gate
+        B1.addApproval('VRFY', -1) # should go to check
+        B2.addApproval('VRFY', 1)  # should go to gate
+        B1.addApproval('APRV', 1)
+        B2.addApproval('APRV', 1)
+        B1.setDependsOn(A, 1)
+        B2.setDependsOn(A, 1)
+        self.fake_gerrit.addEvent(A.addApproval('APRV', 1))
+        # Jobs are being held in build to make sure that 3,1 has time
+        # to enqueue behind 1,1 so that the test is more
+        # deterministic.
+        self.waitUntilSettled()
+        self.worker.hold_jobs_in_build = False
+        self.worker.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(len(self.history), 3)
+        for job in self.history:
+            if job.changes == '1,1':
+                self.assertEqual(job.name, 'project-gate')
+            elif job.changes == '2,1':
+                self.assertEqual(job.name, 'project-check')
+            elif job.changes == '1,1 3,1':
+                self.assertEqual(job.name, 'project-gate')
+            else:
+                raise Exception("Unknown job")
+
+    def test_zuul_trigger_project_change_merged(self):
+        "Test Zuul trigger event: project-change-merged"
+        self.config.set('zuul', 'layout_config',
+                        'tests/fixtures/layout-zuultrigger-merged.yaml')
+        self.sched.reconfigure(self.config)
+        self.registerJobs()
+
+        # This test has the following three changes:
+        # A, B, C;  B conflicts with A, but C does not.
+        # When A is merged, B and C should be checked for conflicts,
+        # and B should receive a -1.
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project', 'master', 'C')
+        A.addPatchset(['conflict'])
+        B.addPatchset(['conflict'])
+        A.addApproval('CRVW', 2)
+        self.fake_gerrit.addEvent(A.addApproval('APRV', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(len(self.history), 1)
+        self.assertEqual(self.history[0].name, 'project-gate')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 1)
+        self.assertEqual(C.reported, 0)
+        self.assertEqual(B.messages[0],
+            "Merge Failed.\n\nThis change was unable to be automatically "
+            "merged with the current state of the repository. Please rebase "
+            "your change and upload a new patchset.")
diff --git a/zuul/cmd/server.py b/zuul/cmd/server.py
index d7de85a45..25dab6f42 100755
--- a/zuul/cmd/server.py
+++ b/zuul/cmd/server.py
@@ -87,6 +87,7 @@ class Server(zuul.cmd.ZuulApp):
         self.sched.registerReporter(None, 'smtp')
         self.sched.registerTrigger(None, 'gerrit')
         self.sched.registerTrigger(None, 'timer')
+        self.sched.registerTrigger(None, 'zuul')
         layout = self.sched.testConfig(self.config.get('zuul',
                                                        'layout_config'))
         if not job_list_path:
@@ -145,6 +146,7 @@ class Server(zuul.cmd.ZuulApp):
         import zuul.reporter.smtp
         import zuul.trigger.gerrit
         import zuul.trigger.timer
+        import zuul.trigger.zuultrigger
         import zuul.webapp
         import zuul.rpclistener
 
@@ -163,6 +165,7 @@ class Server(zuul.cmd.ZuulApp):
         merger = zuul.merger.client.MergeClient(self.config, self.sched)
         gerrit = zuul.trigger.gerrit.Gerrit(self.config, self.sched)
         timer = zuul.trigger.timer.Timer(self.config, self.sched)
+        zuultrigger = zuul.trigger.zuultrigger.ZuulTrigger(self.config, self.sched)
         if self.config.has_option('zuul', 'status_expiry'):
             cache_expiry = self.config.getint('zuul', 'status_expiry')
         else:
@@ -185,6 +188,7 @@ class Server(zuul.cmd.ZuulApp):
         self.sched.setMerger(merger)
         self.sched.registerTrigger(gerrit)
         self.sched.registerTrigger(timer)
+        self.sched.registerTrigger(zuultrigger)
         self.sched.registerReporter(gerrit_reporter)
         self.sched.registerReporter(smtp_reporter)
 
diff --git a/zuul/layoutvalidator.py b/zuul/layoutvalidator.py
index 9a173ffda..b481e6f9e 100644
--- a/zuul/layoutvalidator.py
+++ b/zuul/layoutvalidator.py
@@ -64,8 +64,16 @@ class LayoutSchema(object):
 
     timer_trigger = {v.Required('time'): str}
 
-    trigger = v.Required(v.Any({'gerrit': toList(gerrit_trigger)},
-                               {'timer': toList(timer_trigger)}))
+    zuul_trigger = {v.Required('event'):
+                    toList(v.Any('parent-change-enqueued',
+                                 'project-change-merged')),
+                    'pipeline': toList(str),
+                    'require-approval': toList(require_approval),
+                    }
+
+    trigger = v.Required({'gerrit': toList(gerrit_trigger),
+                          'timer': toList(timer_trigger),
+                          'zuul': toList(zuul_trigger)})
 
     report_actions = {'gerrit': variable_dict,
                       'smtp': {'to': str,
diff --git a/zuul/lib/gerrit.py b/zuul/lib/gerrit.py
index 30fb6fed3..52e60578a 100644
--- a/zuul/lib/gerrit.py
+++ b/zuul/lib/gerrit.py
@@ -144,6 +144,23 @@ class Gerrit(object):
                        (pprint.pformat(data)))
         return data
 
+    def simpleQuery(self, query):
+        args = '--current-patch-set'
+        cmd = 'gerrit query --format json %s %s' % (
+            args, query)
+        out, err = self._ssh(cmd)
+        if not out:
+            return False
+        lines = out.split('\n')
+        if not lines:
+            return False
+        data = [json.loads(line) for line in lines[:-1]]
+        if not data:
+            return False
+        self.log.debug("Received data from Gerrit query: \n%s" %
+                       (pprint.pformat(data)))
+        return data
+
     def _open(self):
         client = paramiko.SSHClient()
         client.load_system_host_keys()
diff --git a/zuul/model.py b/zuul/model.py
index 8b9724170..77ab68bdf 100644
--- a/zuul/model.py
+++ b/zuul/model.py
@@ -947,6 +947,8 @@ class TriggerEvent(object):
         self.newrev = None
         # timer
         self.timespec = None
+        # zuultrigger
+        self.pipeline_name = None
         # For events that arrive with a destination pipeline (eg, from
         # an admin command, etc):
         self.forced_pipeline = None
@@ -1026,7 +1028,7 @@ class BaseFilter(object):
 class EventFilter(BaseFilter):
     def __init__(self, trigger, types=[], branches=[], refs=[],
                  event_approvals={}, comments=[], emails=[], usernames=[],
-                 timespecs=[], required_approvals=[]):
+                 timespecs=[], required_approvals=[], pipelines=[]):
         super(EventFilter, self).__init__(
             required_approvals=required_approvals)
         self.trigger = trigger
@@ -1036,12 +1038,14 @@ class EventFilter(BaseFilter):
         self._comments = comments
         self._emails = emails
         self._usernames = usernames
+        self._pipelines = pipelines
         self.types = [re.compile(x) for x in types]
         self.branches = [re.compile(x) for x in branches]
         self.refs = [re.compile(x) for x in refs]
         self.comments = [re.compile(x) for x in comments]
         self.emails = [re.compile(x) for x in emails]
         self.usernames = [re.compile(x) for x in usernames]
+        self.pipelines = [re.compile(x) for x in pipelines]
         self.event_approvals = event_approvals
         self.timespecs = timespecs
 
@@ -1050,6 +1054,8 @@ class EventFilter(BaseFilter):
 
         if self._types:
             ret += ' types: %s' % ', '.join(self._types)
+        if self._pipelines:
+            ret += ' pipelines: %s' % ', '.join(self._pipelines)
         if self._branches:
             ret += ' branches: %s' % ', '.join(self._branches)
         if self._refs:
@@ -1081,6 +1087,14 @@ class EventFilter(BaseFilter):
         if self.types and not matches_type:
             return False
 
+        # pipelines are ORed
+        matches_pipeline = False
+        for epipe in self.pipelines:
+            if epipe.match(event.pipeline_name):
+                matches_pipeline = True
+        if self.pipelines and not matches_pipeline:
+            return False
+
         # branches are ORed
         matches_branch = False
         for branch in self.branches:
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index eb57f9329..665e5283c 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -1,4 +1,4 @@
-# Copyright 2012 Hewlett-Packard Development Company, L.P.
+# Copyright 2012-2014 Hewlett-Packard Development Company, L.P.
 # Copyright 2013 OpenStack Foundation
 # Copyright 2013 Antoine "hashar" Musso
 # Copyright 2013 Wikimedia Foundation Inc.
@@ -326,12 +326,20 @@ class Scheduler(threading.Thread):
                                     required_approvals=
                                     toList(trigger.get('require-approval')))
                     manager.event_filters.append(f)
-            elif 'timer' in conf_pipeline['trigger']:
+            if 'timer' in conf_pipeline['trigger']:
                 for trigger in toList(conf_pipeline['trigger']['timer']):
                     f = EventFilter(trigger=self.triggers['timer'],
                                     types=['timer'],
                                     timespecs=toList(trigger['time']))
                     manager.event_filters.append(f)
+            if 'zuul' in conf_pipeline['trigger']:
+                for trigger in toList(conf_pipeline['trigger']['zuul']):
+                    f = EventFilter(trigger=self.triggers['zuul'],
+                                    types=toList(trigger['event']),
+                                    pipelines=toList(trigger.get('pipeline')),
+                                    required_approvals=
+                                    toList(trigger.get('require-approval')))
+                    manager.event_filters.append(f)
 
         for project_template in data.get('project-templates', []):
             # Make sure the template only contains valid pipelines
@@ -1153,6 +1161,7 @@ class BasePipelineManager(object):
                 item.enqueue_time = enqueue_time
             self.reportStats(item)
             self.enqueueChangesBehind(change, quiet, ignore_requirements)
+            self.sched.triggers['zuul'].onChangeEnqueued(item.change, self.pipeline)
         else:
             self.log.error("Unable to find change queue for project %s" %
                            change.project)
@@ -1427,6 +1436,7 @@ class BasePipelineManager(object):
                 change_queue.increaseWindowSize()
                 self.log.debug("%s window size increased to %s" %
                                (change_queue, change_queue.window))
+                self.sched.triggers['zuul'].onChangeMerged(item.change)
 
     def _reportItem(self, item):
         self.log.debug("Reporting change %s" % item.change)
diff --git a/zuul/trigger/gerrit.py b/zuul/trigger/gerrit.py
index d2cd7fc9c..6a2c362eb 100644
--- a/zuul/trigger/gerrit.py
+++ b/zuul/trigger/gerrit.py
@@ -323,6 +323,14 @@ class Gerrit(object):
             raise
         return change
 
+    def getProjectOpenChanges(self, project):
+        data = self.gerrit.simpleQuery("project:%s status:open" % project.name)
+        changes = []
+        for record in data:
+            changes.append(self._getChange(record['number'],
+                                           record['currentPatchSet']['number']))
+        return changes
+
     def updateChange(self, change):
         self.log.info("Updating information for %s,%s" %
                       (change.number, change.patchset))
diff --git a/zuul/trigger/zuultrigger.py b/zuul/trigger/zuultrigger.py
new file mode 100644
index 000000000..436311bbd
--- /dev/null
+++ b/zuul/trigger/zuultrigger.py
@@ -0,0 +1,117 @@
+# Copyright 2012-2014 Hewlett-Packard Development Company, L.P.
+# Copyright 2013 OpenStack Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import logging
+from zuul.model import TriggerEvent
+
+
+class ZuulTrigger(object):
+    name = 'zuul'
+    log = logging.getLogger("zuul.ZuulTrigger")
+
+    def __init__(self, config, sched):
+        self.sched = sched
+        self.config = config
+        self._handle_parent_change_enqueued_events = False
+        self._handle_project_change_merged_events = False
+
+    def stop(self):
+        pass
+
+    def isMerged(self, change, head=None):
+        raise Exception("Zuul trigger does not support checking if "
+                        "a change is merged.")
+
+    def canMerge(self, change, allow_needs):
+        raise Exception("Zuul trigger does not support checking if "
+                        "a change can merge.")
+
+    def maintainCache(self, relevant):
+        return
+
+    def onChangeMerged(self, change):
+        # Called each time zuul merges a change
+        if self._handle_project_change_merged_events:
+            try:
+                self._createProjectChangeMergedEvents(change)
+            except Exception:
+                self.log.exception("Unable to create project-change-merged events for %s" % (change,))
+
+    def onChangeEnqueued(self, change, pipeline):
+        # Called each time a change is enqueued in a pipeline
+        if self._handle_parent_change_enqueued_events:
+            try:
+                self._createParentChangeEnqueuedEvents(change, pipeline)
+            except Exception:
+                self.log.exception("Unable to create parent-change-enqueued events for %s in %s" % (change, pipeline))
+
+    def _createProjectChangeMergedEvents(self, change):
+        changes = self.sched.triggers['gerrit'].getProjectOpenChanges(change.project)
+        for change in changes:
+            self._createProjectChangeMergedEvent(change)
+
+    def _createProjectChangeMergedEvent(self, change):
+        event = TriggerEvent()
+        event.type = 'project-change-merged'
+        event.trigger_name = self.name
+        event.project_name = change.project.name
+        event.change_number = change.number
+        event.branch = change.branch
+        event.change_url = change.url
+        event.patch_number = change.patchset
+        event.refspec = change.refspec
+        self.sched.addEvent(event)
+
+    def _createParentChangeEnqueuedEvents(self, change, pipeline):
+        self.log.debug("Checking for changes needing %s:" % change)
+        if not hasattr(change, 'needed_by_changes'):
+            self.log.debug("  Changeish does not support dependencies")
+            return
+        for needs in change.needed_by_changes:
+            self._createParentChangeEnqueuedEvent(needs, pipeline)
+
+    def _createParentChangeEnqueuedEvent(self, change, pipeline):
+        event = TriggerEvent()
+        event.type = 'parent-change-enqueued'
+        event.trigger_name = self.name
+        event.pipeline_name = pipeline.name
+        event.project_name = change.project.name
+        event.change_number = change.number
+        event.branch = change.branch
+        event.change_url = change.url
+        event.patch_number = change.patchset
+        event.refspec = change.refspec
+        self.sched.addEvent(event)
+
+    def postConfig(self):
+        self._handle_parent_change_enqueued_events = False
+        self._handle_project_change_merged_events = False
+        for pipeline in self.sched.layout.pipelines.values():
+            for ef in pipeline.manager.event_filters:
+                if ef.trigger != self:
+                    continue
+                if 'parent-change-enqueued' in ef._types:
+                    self._handle_parent_change_enqueued_events = True
+                elif 'project-change-merged' in ef._types:
+                    self._handle_project_change_merged_events = True
+
+    def getChange(self, number, patchset, refresh=False):
+        raise Exception("Zuul trigger does not support changes.")
+
+    def getGitUrl(self, project):
+        raise Exception("Zuul trigger does not support changes.")
+
+    def getGitwebUrl(self, project, sha=None):
+        raise Exception("Zuul trigger does not support changes.")