Bug 1279676 - Support --rebuild try flag to schedule tests N times. r=dustin

MozReview-Commit-ID: Lrxi8t53nwy

If a developer adds '--rebuild N' to their try syntax they will get test jobs scheduled N times.
This is useful to determine intermittency rate.

This fixes a regression due to the recent refactoring on how we schedule tasks.

--HG--
extra : rebase_source : 355ca631353015bf63461c194168d753efd6958e

taskcluster/docs/attributes.rst

@@ -19,6 +19,19 @@ kind
 A task's ``kind`` attribute gives the name of the kind that generated it, e.g.,
 ``build`` or ``legacy``.
 
+task_duplicates
+===============
+
+This is used to indicate that we want multiple copies of the task created.
+This feature is used to track down intermittent job failures.
+
+If this value is set to N, the task-creation machinery will create a total of N
+copies of the task.  Only the first copy will be included in the taskgraph
+output artifacts, although all tasks will be contained in the same taskGroup.
+
+While most attributes are considered read-only, target task methods may alter
+this attribute of tasks they include in the target set.
+
 build_platform
 ==============
 

taskcluster/taskgraph/create.py

@@ -54,6 +54,7 @@ def create_tasks(taskgraph, label_to_taskid):
         # that.
         for task_id in taskgraph.graph.visit_postorder():
             task_def = taskgraph.tasks[task_id].task
+            attributes = taskgraph.tasks[task_id].attributes
             # 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.
@@ -72,6 +73,12 @@ def create_tasks(taskgraph, label_to_taskid):
             fs[task_id] = e.submit(_create_task, session, task_id,
                                    taskid_to_label[task_id], task_def)
 
+            # Schedule tasks as many times as task_duplicates indicates
+            for i in range(1, attributes.get('task_duplicates', 1)):
+                # We use slugid() since we want a distinct task id
+                fs[task_id] = e.submit(_create_task, session, slugid(),
+                                       taskid_to_label[task_id], task_def)
+
         # Wait for all futures to complete.
         for f in futures.as_completed(fs.values()):
             f.result()

taskcluster/taskgraph/target_tasks.py

@@ -42,8 +42,17 @@ def target_tasks_try_option_syntax(full_task_graph, parameters):
     """Generate a list of target tasks based on try syntax in
     parameters['message'] and, for context, the full task graph."""
     options = try_option_syntax.TryOptionSyntax(parameters['message'], full_task_graph)
-    return [t.label for t in full_task_graph.tasks.itervalues()
-            if options.task_matches(t.attributes)]
+    target_tasks_labels = [t.label for t in full_task_graph.tasks.itervalues()
+                           if options.task_matches(t.attributes)]
+
+    # If the developer wants test jobs to be rebuilt N times we add that value here
+    if int(options.trigger_tests) > 1:
+        for l in target_tasks_labels:
+            task = full_task_graph[l]
+            if 'unittest_suite' in task.attributes:
+                task.attributes['task_duplicates'] = options.trigger_tests
+
+    return target_tasks_labels
 
 
 @_target_task('all_builds_and_tests')