ashb commented on a change in pull request #11467:
URL: https://github.com/apache/airflow/pull/11467#discussion_r512588189
##########
File path: docs/scheduler.rst
##########
@@ -65,3 +65,72 @@ If you want to use 'external trigger' to run future-dated
execution dates, set `
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.
+
+Running more than one scheduler
+-------------------------------
+
+Airflow 2.0 is the first release that officially supports running more one
scheduler concurrently -- both for
+performance reasons and for resiliency.
+
+Overview
+""""""""
+
+The HA scheduler is written to take advantage of the existing metadata
database. This was primarily done for
+operational simplicity: every component already has to speak to this DB, and
by not using direct communication
+or consensus algorithm between schedulers (Raft, Paxos, etc.) nor another
consensus tool (Apache Zookeeper, or
+Consul for instance) we have kept the "operational surface area" to a minimum.
Review comment:
Hmmm, not sure about this one -- I like the idea, but I think I'd rather
the docs be the source of truth rather than linking to the AIP.
I might link to the AIP for now though.
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