github: Do not process comment events for regular issues

Github uses the same webhook event for comments added to both regular
issues and pull requests. Currently, Zuul will attempt to process
non-PR issues which results in a number of API requests as it attempts
to find non-existent pull requests.  This needless traffic can cause
rate-limiting issues in high traffic installations. The webhook body contains
an extra key when comments originate from a PR, which we can use to filter.

Change-Id: I9ab2cc7f37273126cfc669ebf2404215ca6c6f80

tests/base.py

@@ -702,7 +702,7 @@ class FakeGithubPullRequest(object):
         self.comments.append(message)
         self._updateTimeStamp()
 
-    def getCommentAddedEvent(self, text):
+    def getIssueCommentAddedEvent(self, text):
         name = 'issue_comment'
         data = {
             'action': 'created',
@@ -721,6 +721,15 @@ class FakeGithubPullRequest(object):
         }
         return (name, data)
 
+    def getCommentAddedEvent(self, text):
+        name, data = self.getIssueCommentAddedEvent(text)
+        # A PR comment has an additional 'pull_request' key in the issue data
+        data['issue']['pull_request'] = {
+            'url': 'http://%s/api/v3/repos/%s/pull/%s' % (
+                self.github.server, self.project, self.number)
+        }
+        return (name, data)
+
     def getReviewAddedEvent(self, review):
         name = 'pull_request_review'
         data = {

tests/unit/test_github_driver.py

@@ -101,6 +101,13 @@ class TestGithubDriver(ZuulTestCase):
         self.waitUntilSettled()
         self.assertEqual(2, len(self.history))
 
+        # Test an unmatched comment, history should remain the same
+        C = self.fake_github.openFakePullRequest('org/project', 'master', 'C')
+        self.fake_github.emitEvent(
+            C.getIssueCommentAddedEvent('a non-PR issue comment'))
+        self.waitUntilSettled()
+        self.assertEqual(2, len(self.history))
+
     @simple_layout('layouts/push-tag-github.yaml', driver='github')
     def test_tag_event(self):
         self.executor_server.hold_jobs_in_build = True

zuul/driver/github/githubconnection.py

@@ -293,6 +293,9 @@ class GithubEventConnector(threading.Thread):
         action = body.get('action')
         if action != 'created':
             return
+        if not body.get('issue', {}).get('pull_request'):
+            # Do not process non-PR issue comment
+            return
         pr_body = self._issue_to_pull_request(body)
         number = body.get('issue').get('number')
         project_name = body.get('repository').get('full_name')