title: Why tasks are stuck in None state in Airflow 1.10.2 after a trigger_dag
body: <p>I have a dummy DAG that I want to start episodically by setting its <code>start_date</code> to <code>today</code> and letting its schedul interval to <code>daily</code></p>
  
  <p>here is the DAG code:</p>
  
  <pre class="lang-py prettyprint-override"><code>#!/usr/bin/env python
  # -*- coding: utf-8 -*-
  # -*- airflow: DAG -*-
  import logging
  
  from airflow import DAG
  from airflow.operators.dummy_operator import DummyOperator
  from airflow.operators.python_operator import PythonOperator
  from datetime import datetime
  
  logger = logging.getLogger("DummyDAG")
  
  
  def execute_python_function():
      logging.info("HEY YO !!!")
      return True
  
  
  dag = DAG(dag_id='dummy_dag',
            start_date=datetime.today())
  
  start = DummyOperator(task_id='start', dag=dag)
  end = DummyOperator(task_id='end', dag=dag)
  
  py_operator = PythonOperator(task_id='exec_function',
                               python_callable=execute_python_function,
                               dag=dag)
  
  start &gt;&gt; py_operator &gt;&gt; end
  </code></pre>
  
  <p>In Airflow 1.9.0, when I do an <code>airflow trigger_dag -e 20190701</code> the DAG Run is created, Tasks Instances are created, scheduled and executed. </p>
  
  <p>However, in Airflow 1.10.2 the DAG Run is created Task Instances too but they are stuck in <code>None</code> state. </p>
  
  <p>for both versions the depends_on_past is <code>False</code></p>
  
  <p>Here are the details of the <code>start</code> task in Airflow 1.9.0 (it is executed, with success, after some time)</p>
  
  <pre><code>Task Instance Details
  
  Dependencies Blocking Task From Getting Scheduled
  
  Dependency:         Reason
  Dagrun Running:     Task instance's dagrun was not in the 'running' state but in the state 'success'.
  Task Instance State:    Task is in the 'success' state which is not a valid state for execution. The task must be cleared in order to be run.
  Execution Date:     The execution date is 2019-07-10T00:00:00 but this is before the task's start date 2019-07-11T08:45:18.230876.
  Execution Date:     The execution date is 2019-07-10T00:00:00 but this is before the task's DAG's start date 2019-07-11T08:45:18.230876.
  
  Task instance attribute
  
  Attribute   Value
  dag_id  dummy_dag
  duration    None
  end_date    2019-07-10 16:32:10.372976
  execution_date  2019-07-10 00:00:00
  generate_command    &lt;function generate_command at 0x7fc9fcc85b90&gt;
  hostname    airflow-worker-5dc5b999b6-2l5cp
  is_premature    False
  job_id  None
  key     ('dummy_dag', 'start', datetime.datetime(2019, 7, 10, 0, 0))
  log     &lt;logging.Logger object at 0x7fca014e7f10&gt;
  log_filepath    /home/airflow/gcs/logs/dummy_dag/start/2019-07-10T00:00:00.log
  log_url     https://i39907f7014685e91-tp.appspot.com/admin/airflow/log?dag_id=dummy_dag&amp;task_id=start&amp;execution_date=2019-07-10T00:00:00
  logger  &lt;logging.Logger object at 0x7fca014e7f10&gt;
  mark_success_url    https://i39907f7014685e91-tp.appspot.com/admin/airflow/success?task_id=start&amp;dag_id=dummy_dag&amp;execution_date=2019-07-10T00:00:00&amp;upstream=false&amp;downstream=false
  max_tries   0
  metadata    MetaData(bind=None)
  next_try_number     2
  operator    None
  pid     180712
  pool    None
  previous_ti     None
  priority_weight     3
  queue   default
  queued_dttm     None
  run_as_user     None
  start_date  2019-07-10 16:32:08.483531
  state   success
  task    &lt;Task(DummyOperator): start&gt;
  task_id     start
  test_mode   False
  try_number  2
  unixname    airflow
  
  Task Attributes
  
  Attribute   Value
  adhoc   False
  dag     &lt;DAG: dummy_dag&gt;
  dag_id  dummy_dag
  depends_on_past     False
  deps    set([&lt;TIDep(Not In Retry Period)&gt;, &lt;TIDep(Previous Dagrun State)&gt;, &lt;TIDep(Trigger Rule)&gt;])
  downstream_list     [&lt;Task(PythonOperator): exec_function&gt;]
  downstream_task_ids     ['exec_function']
  email   None
  email_on_failure    True
  email_on_retry  True
  end_date    None
  execution_timeout   None
  log     &lt;logging.Logger object at 0x7fc9e2085350&gt;
  logger  &lt;logging.Logger object at 0x7fc9e2085350&gt;
  max_retry_delay     None
  on_failure_callback     None
  on_retry_callback   None
  on_success_callback     None
  owner   Airflow
  params  {}
  pool    None
  priority_weight     1
  priority_weight_total   3
  queue   default
  resources   {'disk': {'_qty': 512, '_units_str': 'MB', '_name': 'Disk'}, 'gpus': {'_qty': 0, '_units_str': 'gpu(s)', '_name': 'GPU'}, 'ram': {'_qty': 512, '_units_str': 'MB', '_name': 'RAM'}, 'cpus': {'_qty': 1, '_units_str': 'core(s)', '_name': 'CPU'}}
  retries     0
  retry_delay     0:05:00
  retry_exponential_backoff   False
  run_as_user     None
  schedule_interval   1 day, 0:00:00
  sla     None
  start_date  2019-07-11 08:45:18.230876
  task_concurrency    None
  task_id     start
  task_type   DummyOperator
  template_ext    []
  template_fields     ()
  trigger_rule    all_success
  ui_color    #e8f7e4
  ui_fgcolor  #000
  upstream_list   []
  upstream_task_ids   []
  wait_for_downstream     False
  
  </code></pre>
  
  <p>Details of the start task in Airflow 1.10.2</p>
  
  <pre><code>Task Instance Details
  Dependencies Blocking Task From Getting Scheduled
  
  Dependency  Reason
  Execution Date  The execution date is 2019-07-11T00:00:00+00:00 but this is before the task's start date 2019-07-11T08:53:32.593360+00:00.
  Execution Date  The execution date is 2019-07-11T00:00:00+00:00 but this is before the task's DAG's start date 2019-07-11T08:53:32.593360+00:00.
  
  
  Task Instance Attributes
  
  Attribute   Value
  dag_id  dummy_dag
  duration    None
  end_date    None
  execution_date  2019-07-11T00:00:00+00:00
  executor_config     {}
  generate_command    &lt;function generate_command at 0x7f4621301578&gt;
  hostname    
  is_premature    False
  job_id  None
  key     ('dummy_dag', 'start', &lt;Pendulum [2019-07-11T00:00:00+00:00]&gt;, 1)
  log     &lt;logging.Logger object at 0x7f4624883350&gt;
  log_filepath    /home/airflow/gcs/logs/dummy_dag/start/2019-07-11T00:00:00+00:00.log
  log_url     https://a15d189066a5c65ee-tp.appspot.com/admin/airflow/log?dag_id=dummy_dag&amp;task_id=start&amp;execution_date=2019-07-11T00%3A00%3A00%2B00%3A00
  logger  &lt;logging.Logger object at 0x7f4624883350&gt;
  mark_success_url    https://a15d189066a5c65ee-tp.appspot.com/admin/airflow/success?task_id=start&amp;dag_id=dummy_dag&amp;execution_date=2019-07-11T00%3A00%3A00%2B00%3A00&amp;upstream=false&amp;downstream=false
  max_tries   0
  metadata    MetaData(bind=None)
  next_try_number     1
  operator    None
  pid     None
  pool    None
  previous_ti     None
  priority_weight     3
  queue   default
  queued_dttm     None
  raw     False
  run_as_user     None
  start_date  None
  state   None
  task    &lt;Task(DummyOperator): start&gt;
  task_id     start
  test_mode   False
  try_number  1
  unixname    airflow
  
  
  Task Attributes
  
  
  Attribute   Value
  adhoc   False
  dag     &lt;DAG: dummy_dag&gt;
  dag_id  dummy_dag
  depends_on_past     False
  deps    set([&lt;TIDep(Previous Dagrun State)&gt;, &lt;TIDep(Trigger Rule)&gt;, &lt;TIDep(Not In Retry Period)&gt;])
  downstream_list     [&lt;Task(PythonOperator): exec_function&gt;]
  downstream_task_ids     set(['exec_function'])
  email   None
  email_on_failure    True
  email_on_retry  True
  end_date    None
  execution_timeout   None
  executor_config     {}
  inlets  []
  lineage_data    None
  log     &lt;logging.Logger object at 0x7f460b467e10&gt;
  logger  &lt;logging.Logger object at 0x7f460b467e10&gt;
  max_retry_delay     None
  on_failure_callback     None
  on_retry_callback   None
  on_success_callback     None
  outlets     []
  owner   Airflow
  params  {}
  pool    None
  priority_weight     1
  priority_weight_total   3
  queue   default
  resources   {'disk': {'_qty': 512, '_units_str': 'MB', '_name': 'Disk'}, 'gpus': {'_qty': 0, '_units_str': 'gpu(s)', '_name': 'GPU'}, 'ram': {'_qty': 512, '_units_str': 'MB', '_name': 'RAM'}, 'cpus': {'_qty': 1, '_units_str': 'core(s)', '_name': 'CPU'}}
  retries     0
  retry_delay     0:05:00
  retry_exponential_backoff   False
  run_as_user     None
  schedule_interval   1 day, 0:00:00
  sla     None
  start_date  2019-07-11T08:53:32.593360+00:00
  task_concurrency    None
  task_id     start
  task_type   DummyOperator
  template_ext    []
  template_fields     ()
  trigger_rule    all_success
  ui_color    #e8f7e4
  ui_fgcolor  #000
  upstream_list   []
  upstream_task_ids   set([])
  wait_for_downstream     False
  weight_rule     downstream
  
  </code></pre>