Running Airflow in Docker - Tutorial dags backfill tutorial example fails with TypeError: cannot serialize '_io.TextIOWrapper' object

Hello, Apologizes in advance if this is a newbie mistake. I’m working through the tutorial using Docker Desktop for Mac locally using the docker-compose from the Running Airflow in Docker. I’m copying the tutorial code as is as except for replacing airflow with ./airflow.sh to run in docker. All the commands work as expected except for the backfill example, which fails with TypeError: cannot serialize '_io.TextIOWrapper' object. Please advise.

# start your backfill on a date range
 % ./airflow.sh dags backfill tutorial \
    --start-date 2015-06-01 \
    --end-date 2015-06-07
Creating airflow_tut_airflow-worker_run ... done
BACKEND=postgresql+psycopg2
DB_HOST=postgres
DB_PORT=5432

/home/airflow/.local/lib/python3.6/site-packages/airflow/cli/commands/dag_command.py:62 PendingDeprecationWarning: --ignore-first-depends-on-past is deprecated as the value is always set to True
[2021-02-23 08:11:03,363] {dagbag.py:448} INFO - Filling up the DagBag from /opt/airflow/dags
[2021-02-23 08:11:04,308] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-01T00:00:00+00:00', '--ignore-depends-on-past', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
[2021-02-23 08:11:04,343] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-02T00:00:00+00:00', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
[2021-02-23 08:11:04,375] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-03T00:00:00+00:00', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
[2021-02-23 08:11:04,406] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-04T00:00:00+00:00', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
[2021-02-23 08:11:04,446] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-05T00:00:00+00:00', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
[2021-02-23 08:11:04,487] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-06T00:00:00+00:00', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
[2021-02-23 08:11:04,573] {base_executor.py:82} INFO - Adding to queue: ['airflow', 'tasks', 'run', 'tutorial', 'print_date', '2015-06-07T00:00:00+00:00', '--local', '--pool', 'default_pool', '--subdir', '/home/airflow/.local/lib/python3.6/site-packages/airflow/example_dags/tutorial.py']
Traceback (most recent call last):
  File "/home/airflow/.local/bin/airflow", line 8, in <module>
    sys.exit(main())
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/__main__.py", line 40, in main
    args.func(args)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/cli/cli_parser.py", line 48, in command
    return func(*args, **kwargs)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/utils/cli.py", line 89, in wrapper
    return f(*args, **kwargs)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/cli/commands/dag_command.py", line 116, in dag_backfill
    run_backwards=args.run_backwards,
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/models/dag.py", line 1706, in run
    job.run()
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/jobs/base_job.py", line 237, in run
    self._execute()
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/jobs/backfill_job.py", line 805, in _execute
    session=session,
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/utils/session.py", line 62, in wrapper
    return func(*args, **kwargs)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/jobs/backfill_job.py", line 727, in _execute_for_run_dates
    session=session,
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/utils/session.py", line 62, in wrapper
    return func(*args, **kwargs)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/jobs/backfill_job.py", line 602, in _process_backfill_task_instances
    executor.heartbeat()
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/executors/base_executor.py", line 158, in heartbeat
    self.trigger_tasks(open_slots)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/executors/celery_executor.py", line 263, in trigger_tasks
    self._process_tasks(task_tuples_to_send)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/executors/celery_executor.py", line 272, in _process_tasks
    key_and_async_results = self._send_tasks_to_celery(task_tuples_to_send)
  File "/home/airflow/.local/lib/python3.6/site-packages/airflow/executors/celery_executor.py", line 332, in _send_tasks_to_celery
    send_task_to_executor, task_tuples_to_send, chunksize=chunksize
  File "/usr/local/lib/python3.6/multiprocessing/pool.py", line 266, in map
    return self._map_async(func, iterable, mapstar, chunksize).get()
  File "/usr/local/lib/python3.6/multiprocessing/pool.py", line 644, in get
    raise self._value
  File "/usr/local/lib/python3.6/multiprocessing/pool.py", line 424, in _handle_tasks
    put(task)
  File "/usr/local/lib/python3.6/multiprocessing/connection.py", line 206, in send
    self._send_bytes(_ForkingPickler.dumps(obj))
  File "/usr/local/lib/python3.6/multiprocessing/reduction.py", line 51, in dumps
    cls(buf, protocol).dump(obj)
TypeError: cannot serialize '_io.TextIOWrapper' object

 % docker --version
Docker version 20.10.2, build 2291f61
% docker-compose --version
docker-compose version 1.27.4, build 40524192
% docker ps
CONTAINER ID   IMAGE                  COMMAND                  CREATED          STATUS                    PORTS                              NAMES
cfb65ccd5432   apache/airflow:2.0.1   "/usr/bin/dumb-init …"   21 minutes ago   Up 21 minutes             8080/tcp                           airflow_tut_airflow-scheduler_1
46b70dfa6c90   apache/airflow:2.0.1   "/usr/bin/dumb-init …"   21 minutes ago   Up 21 minutes             8080/tcp                           airflow_tut_airflow-worker_1
37065f3e3d9b   apache/airflow:2.0.1   "/usr/bin/dumb-init …"   21 minutes ago   Up 21 minutes (healthy)   0.0.0.0:5555->5555/tcp, 8080/tcp   airflow_tut_flower_1
e498390f3c50   apache/airflow:2.0.1   "/usr/bin/dumb-init …"   21 minutes ago   Up 21 minutes (healthy)   0.0.0.0:8080->8080/tcp             airflow_tut_airflow-webserver_1
5844644d1157   postgres:13            "docker-entrypoint.s…"   23 minutes ago   Up 22 minutes (healthy)   5432/tcp                           airflow_tut_postgres_1
929c10f40745   redis:latest           "docker-entrypoint.s…"   23 minutes ago   Up 22 minutes (healthy)   0.0.0.0:6379->6379/tcp             airflow_tut_redis_1

[DougForrest]

Thanks for the response I wasn’t aware there was a large difference. I can confirm that the image apache/airflow:2.0.1-python3.8 also works in my local environment.

[DougForrest]

I updated the docker-compose.yaml default airflow image which fixed the problem.

-  image: ${AIRFLOW_IMAGE_NAME:-apache/airflow:2.0.1}
+   image: ${AIRFLOW_IMAGE_NAME:-apache/airflow:master-python3.8}

Output above shows container was running python3.6. The comments in the docker-compose.yaml state the default should be Default: apache/airflow:master-python3.8

Created pull request for v2-0-stable. Changes are consistent with master branch. https://github.com/apache/airflow/pull/14404