Random failed tasks with no operator and no hostname?

[7yl4r]

I can't see any pattern here, and I have seen this in multiple DAGs since upgrading to v1.9.0.

---

Here are some "Task Instance Attributes" from the "task instance details view" that may be relevant:

attribute	value
Dagrun Running	Task instance's dagrun was not in the 'running' state but in the state 'failed'.
Execution Date	The execution date is 2002-07-13T19:05:00 but this is before the task's start date 2018-05-25T16:45:25.575395.
is_premature	False
max_tries	10
metadata	MetaData(bind=None)
next_try_number	1
operator	None
pid	None
pool	None
previous_ti	None
queue	default
queued_dttm	None
start_date	None
unixname	root

---

Here is a list of the ones I am clearing from the myd01 proc DAG:

[7yl4r]

Potentially relevant issue: AIRFLOW-695 (fix was merged 2017-01)... so we shouldn't be seeing this in v1.9 (released 2017-12)