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  1. Apache Airflow
  2. AIRFLOW-4961

SQL Error when writing Task Failure (using CockroachDB)

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: 1.10.3
    • Fix Version/s: 1.10.4
    • Component/s: database
    • Labels:
      None

      Description

      We're running Airflow against CockroachDB (which is designed to be "compatible" with PostgresSQL https://www.cockroachlabs.com/blog/why-postgres/), but with a few subtle differences https://www.cockroachlabs.com/docs/stable/porting-postgres.html).

       

      It's been fairly painless so far (we've got a few minor tweaks of SQL grammar in our fork, especially around DB migrations), but we've come across something we think is worth merging back to Airflow trunk. It's both not quite correct behaviour in normal operation anyway, and it's a 4 character fix.

      When a task has failed, we get this error writing to the task_fail table in (taskfail.py): 

      value type decimal doesn't match type INT8 of column "duration"

      This is because total_seconds() returns a decimal, but it's assigned to the variable duration, bound to an integer database column here:

       

      self.duration = (self.end_date - self.start_date).total_seconds()
      

       

      https://github.com/apache/airflow/blob/b33b9898677e70ef3fcb4bf03cd28b4077681224/airflow/models/taskfail.py#L53

      A fix looks like:

      self.duration = int((self.end_date - self.start_date).total_seconds())

      which means we're no longer reliant on the database to truncate and cast this correctly,

      The flipside of this argument is documented here: 
      https://www.postgresql.org/message-id/8750.1188249597@sss.pgh.pa.us - postgres made a conscious decision to not throw errors in this situation. I'll ping a copy of this ticket over to Cockroach labs too, to see if they have any thoughts (it's not listed as a current incompatibility, but probably should be). 

       

       From the stacktrace:

      [2019-07-03 09:06:33,402] {{base_task_runner.py:101}} INFO - Job 465548343190323206: Subtask update_snapshot     cursor.execute(statement, parameters)
      [2019-07-03 09:06:33,402] {{base_task_runner.py:101}} INFO - Job 465548343190323206: Subtask update_snapshot sqlalchemy.exc.ProgrammingError: (psycopg2.errors.DatatypeMismatch) value type decimal doesn't match type INT8 of column "duration"
      [2019-07-03 09:06:33,402] {{base_task_runner.py:101}} INFO - Job 465548343190323206: Subtask update_snapshot  [SQL: 'INSERT INTO task_fail (task_id, dag_id, execution_date, start_date, end_date, duration) VALUES (%(task_id)s, %(dag_id)s, %(execution_date)s, %(start_date)s, %(end_date)s, %(duration)s) RETURNING task_fail.id'] [parameters: {'task_id': 'update_snapshot', 'dag_id': 'snapshot_table_update', 'execution_date': <Pendulum [2019-07-03T08:30:46.221467+00:00]>, 'start_date': datetime.datetime(2019, 7, 3, 9, 1, 19, 436714, tzinfo=<TimezoneInfo [UTC, GMT, +00:00:00, STD]>), 'end_date': datetime.datetime(2019, 7, 3, 9, 6, 33, 337921, tzinfo=<Timezone [UTC]>), 'duration': 313.901207}] (Background on this error at: http://sqlalche.me/e/f405)
      

      I'll attach a PR to this ticket in a sec. 

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              • Assignee:
                Unassigned
                Reporter:
                fahran Fahran Wallace
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