Four new metrics have been added into task iteration process:
'tasks.parse_errors': count of errors when parsing the task object
'tasks.skipped': count of task objects skipped because it doesn't
belong to this expirer.
'tasks.delayed': count of objects is still within the delay
'tasks.assigned': count of assigned objects to this expirer
Co-Authored-By: Alistair Coles <alistairncoles@gmail.com>
Co-Authored-By: Clay Gerrard <clay.gerrard@gmail.com>
Change-Id: Ib151c498ba325f39570e963e5b7948080ffcd3d6