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Docs: Fix FAQ on scheduler latency #13969

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Jan 29, 2021
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7 changes: 2 additions & 5 deletions docs/apache-airflow/faq.rst
Original file line number Diff line number Diff line change
Expand Up @@ -205,11 +205,8 @@ This means ``explicit_defaults_for_timestamp`` is disabled in your mysql server
How to reduce airflow dag scheduling latency in production?
-----------------------------------------------------------

- ``parsing_processes``: Scheduler will spawn multiple threads in parallel to parse dags.
This is controlled by ``parsing_processes`` with default value of 2.
User should increase this value to a larger value (e.g numbers of cpus where scheduler runs + 1) in production.
- If you're using Airflow 1.10.x, consider moving to Airflow 2, which has reduced dag scheduling latency dramatically,
and allows for running multiple schedulers.
Airflow 2 has low DAG scheduling latency out of the box (particularly when compared with Airflow 1.10.x),
however if you need more throughput you can :ref:`start multiple schedulers<scheduler:ha>`.

Why next_ds or prev_ds might not contain expected values?
---------------------------------------------------------
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4 changes: 2 additions & 2 deletions docs/apache-airflow/scheduler.rst
Original file line number Diff line number Diff line change
Expand Up @@ -66,11 +66,11 @@ This only has effect if your DAG has no ``schedule_interval``.
If you keep default ``allow_trigger_in_future = False`` and try 'external trigger' to run future-dated execution dates,
the scheduler won't execute it now but the scheduler will execute it in the future once the current date rolls over to the execution date.

.. _scheduler:ha:

Running More Than One Scheduler
-------------------------------

.. _scheduler:ha:

.. versionadded: 2.0.0
Airflow supports running more than one scheduler concurrently -- both for performance reasons and for
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2 changes: 1 addition & 1 deletion docs/build_docs.py
Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ def _promote_new_flags():
print("Still too slow?")
print()
print("You can only build one documentation package:")
print(" ./breeze build-docs --package-filter <PACKAGE-NAME>")
print(" ./breeze build-docs -- --package-filter <PACKAGE-NAME>")
print()
print("This usually takes from 20 seconds to 2 minutes.")
print()
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