Making some refactors to make it easier to cancel the build at any time.

data/model/build.py

@@ -143,24 +143,47 @@ def get_pull_robot_name(trigger):
   return trigger.pull_robot.username
 
 
-def cancel_repository_build(build, work_queue):
+def update_phase(build_uuid, phase):
+  """ A function to change the phase of a build """
+  with db_transaction():
+    try:
+      build = get_repository_build(build_uuid)
+      build.phase = phase
+      build.save()
+      return True
+    except InvalidRepositoryBuildException:
+      return False
+
+
+def create_cancel_build_in_queue(build, build_queue):
+  """ A function to cancel a build before it leaves the queue """
+  def cancel_build():
+    if build.phase != BUILD_PHASE.WAITING or not build.queue_id:
+      return False
+
+    return build_queue.cancel(build.queue_id)
+
+  return cancel_build
+
+
+def cancel_repository_build(build, build_queue):
+  """ This tries to cancel the build returns true if request is successful false if it can't be cancelled """
   with db_transaction():
     # Reload the build for update.
+    # We are loading the build for update so checks should be as quick as possible.
     try:
       build = db_for_update(RepositoryBuild.select().where(RepositoryBuild.id == build.id)).get()
     except RepositoryBuild.DoesNotExist:
       return False
 
-    if build.phase != BUILD_PHASE.WAITING or not build.queue_id:
-      return False
+    cancel_builds = [create_cancel_build_in_queue(build, build_queue), ]
+    for cancelled in cancel_builds:
+      if cancelled():
+        # Delete the build row.
+        build.delete_instance()
+        return True
 
-    # Try to cancel the queue item.
-    if not work_queue.cancel(build.queue_id):
-      return False
-
-    # Delete the build row.
-    build.delete_instance()
-    return True
+    return False
 
 
 def get_archivable_build():