Save superfluous api requests in check run reporting

When reporting the check run result zuul is currently doing four
github api requests:
1. Get repository
2. Get head commit of pr
3. Get check runs of head commit
4. (optional) Create initial version of check run in case start
   reporting is disabled
5. Update check run that has been created in start reporting

The first three requests are basically unneeded if we craft a direct
PATCH request and remember the check run id that has been created in
the start reporting.

This is needed since those run in the critical path of the event
processing and can cause large event processing delays in a very busy
zuul system.

Change-Id: I55df1cc28279bb6923e51686dde8809421486c6a

2 files changed, 74 insertions, 104 deletions

diff --git a/zuul/driver/github/githubconnection.py b/zuul/driver/github/githubconnection.py
index 1ef5f9a8d..9e5c2bbc4 100644
--- a/zuul/driver/github/githubconnection.py
+++ b/zuul/driver/github/githubconnection.py
@@ -1988,13 +1988,27 @@ class GithubConnection(BaseConnection):
         pull_request.remove_label(label)
         log.debug("Removed label %s from %s#%s", label, proj, pr_number)
 
+    def _create_or_update_check(self, github, project_name, check_run_id,
+                                **kwargs):
+        if check_run_id:
+            # Update an existing check run
+            url = github.session.build_url(
+                'repos', project_name, 'check-runs', str(check_run_id))
+            resp = github.session.patch(url, json=kwargs)
+        else:
+            # Create a new check run
+            url = github.session.build_url(
+                'repos', project_name, 'check-runs')
+            resp = github.session.post(url, json=kwargs)
+        resp.raise_for_status()
+        return resp.json().get('id')
+
     def updateCheck(self, project, pr_number, sha, status, completed, context,
                     details_url, message, file_comments, external_id,
-                    zuul_event_id=None):
+                    zuul_event_id=None, check_run_id=None):
         log = get_annotated_logger(self.log, zuul_event_id)
         github = self.getGithubClient(project, zuul_event_id=zuul_event_id)
         self._append_accept_header(github, PREVIEW_CHECKS_ACCEPT)
-        owner, proj = project.split("/")
 
         # Always provide an empty list of actions by default
         actions = []
@@ -2018,7 +2032,7 @@ class GithubConnection(BaseConnection):
                     context
                 )
             )
-            return errors
+            return None, errors
 
         output = {"title": "Summary", "summary": message}
 
@@ -2041,83 +2055,34 @@ class GithubConnection(BaseConnection):
             # conclusion, as the status will always be "completed".
             conclusion = status
 
-            # Unless something went wrong during the start reporting of this
-            # change (e.g. the check_run creation failed), there should already
-            # be a check_run available. If not we will create one.
-            check_runs = []
-
-            repository = github.repository(owner, proj)
-            try:
-                check_runs = [
-                    c for c in repository.commit(sha).check_runs()
-                    if c.name == context
-                ]
-            except github3.exceptions.GitHubException as exc:
-                log.error(
-                    "Could not retrieve existing check runs for %s#%s on "
-                    "sha %s: %s",
-                    project, pr_number, sha, str(exc),
-                )
-
-            if not check_runs:
-                log.debug(
-                    "Could not find check run %s for %s#%s on sha %s. "
-                    "Creating a new one",
-                    context, project, pr_number, sha,
+            if not check_run_id:
+                log.debug("Could not find check run %s for %s#%s on sha %s. "
+                          "Creating a new one", context, project, pr_number,
+                          sha)
+                action = 'create'
+                arguments = dict(
+                    name=context,
+                    head_sha=sha,
+                    conclusion=conclusion,
+                    completed_at=completed_at,
+                    output=output,
+                    details_url=details_url,
+                    external_id=external_id,
+                    actions=actions,
                 )
-
-                try:
-                    check_run = repository.create_check_run(
-                        name=context,
-                        head_sha=sha,
-                        conclusion=conclusion,
-                        completed_at=completed_at,
-                        output=output,
-                        details_url=details_url,
-                        external_id=external_id,
-                        actions=actions,
-                    )
-                except github3.exceptions.GitHubException as exc:
-                    # TODO (felix): Should we retry the check_run creation?
-                    log.error(
-                        "Failed to create check run %s for %s#%s on sha %s: "
-                        "%s",
-                        context, project, pr_number, sha, str(exc)
-                    )
-                    errors.append(
-                        "Failed to create check run {}: {}".format(
-                            context, str(exc)
-                        )
-                    )
             else:
-                check_run = check_runs[0]
-                log.debug(
-                    "Updating existing check run %s for %s#%s on sha %s "
-                    "with status %s",
-                    context, project, pr_number, sha, status,
+                log.debug("Updating existing check run %s for %s#%s on sha %s "
+                          "with status %s", context, project, pr_number, sha,
+                          status)
+                action = 'update'
+                arguments = dict(
+                    conclusion=conclusion,
+                    completed_at=completed_at,
+                    output=output,
+                    details_url=details_url,
+                    external_id=external_id,
+                    actions=actions,
                 )
-
-                try:
-                    check_run.update(
-                        conclusion=conclusion,
-                        completed_at=completed_at,
-                        output=output,
-                        details_url=details_url,
-                        external_id=external_id,
-                        actions=actions,
-                    )
-                except github3.exceptions.GitHubException as exc:
-                    log.error(
-                        "Failed to update check run %s for %s#%s on sha %s: "
-                        "%s",
-                        context, project, pr_number, sha, str(exc),
-                    )
-                    errors.append(
-                        "Failed to update check run {}: {}".format(
-                            context, str(exc)
-                        )
-                    )
-
         else:
             # Add an abort/dequeue action to running check runs
             actions.append(
@@ -2132,35 +2097,33 @@ class GithubConnection(BaseConnection):
                 }
             )
 
-            # Report the start of a check run
-            try:
-                data = dict(
-                    name=context,
-                    head_sha=sha,
-                    status=status,
-                    output=output,
-                    details_url=details_url,
-                    external_id=external_id,
-                    actions=actions,
-                )
+            action = 'create'
+            arguments = dict(
+                name=context,
+                head_sha=sha,
+                status=status,
+                output=output,
+                details_url=details_url,
+                external_id=external_id,
+                actions=actions,
+            )
 
-                url = github.session.build_url('repos', project,
-                                               'check-runs')
-                resp = github.session.post(url, json=data)
-                resp.raise_for_status()
+        # Create/update the check run
+        try:
+            check_run_id = self._create_or_update_check(
+                github,
+                project,
+                check_run_id,
+                **arguments,
+            )
 
-            except requests.exceptions.HTTPError as exc:
-                log.error(
-                    "Failed to create check run %s for %s#%s on sha %s: %s",
-                    context, project, pr_number, sha, str(exc),
-                )
-                errors.append(
-                    "Failed to update check run {}: {}".format(
-                        context, str(exc)
-                    )
-                )
+        except requests.exceptions.HTTPError as exc:
+            log.error("Failed to %s check run %s for %s#%s on sha %s: %s",
+                      action, context, project, pr_number, sha, str(exc))
+            errors.append("Failed to {} check run {}: {}".format(
+                action, context, str(exc)))
 
-        return errors
+        return check_run_id, errors
 
     def _buildAnnotationsFromComments(self, file_comments):
         annotations = []
diff --git a/zuul/driver/github/githubreporter.py b/zuul/driver/github/githubreporter.py
index b2487d61e..0925b50d7 100644
--- a/zuul/driver/github/githubreporter.py
+++ b/zuul/driver/github/githubreporter.py
@@ -245,7 +245,8 @@ class GithubReporter(BaseReporter):
             }
         )
 
-        return self.connection.updateCheck(
+        state = item.dynamic_state[self.connection.connection_name]
+        check_run_id, errors = self.connection.updateCheck(
             project,
             pr_number,
             sha,
@@ -257,8 +258,14 @@ class GithubReporter(BaseReporter):
             file_comments,
             external_id,
             zuul_event_id=item.event,
+            check_run_id=state.get('check_run_id')
         )
 
+        if check_run_id:
+            state['check_run_id'] = check_run_id
+
+        return errors
+
     def setLabels(self, item):
         log = get_annotated_logger(self.log, item.event)
         project = item.change.project.name