Branching related additions to docs

lue828 · Nov 23, 2015 · 4497b53 · 4497b53
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diff --git a/airflow/operators/python_operator.py b/airflow/operators/python_operator.py
@@ -83,6 +83,8 @@ class BranchPythonOperator(PythonOperator):
     Note that using tasks with ``depends_on_past=True`` downstream from
     ``BranchPythonOperator`` is logically unsound as ``skipped`` status
     will invariably lead to block tasks that depend on their past successes.
+    ``skipped`` states propagates where all directly upstream tasks are
+    ``skipped``.
     """
     def execute(self, context):
         branch = super(BranchPythonOperator, self).execute(context)

diff --git a/docs/concepts.rst b/docs/concepts.rst
@@ -211,6 +211,12 @@ is followed, and all of the other paths are skipped.
 The task_id returned by the Python function has to be referencing a task
 directly downstream from the BranchPythonOperator task.
 
+Note that using tasks with ``depends_on_past=True`` downstream from
+``BranchPythonOperator`` is logically unsound as ``skipped`` status
+will invariably lead to block tasks that depend on their past successes.
+``skipped`` states propagates where all directly upstream tasks are
+``skipped``.
+
 
 SLAs
 ''''