Make sure you have checked _all_ steps below. ### Jira
- [X] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR" - https://issues.apache.org/jira/browse/AIRFLOW-XXX - In case you are fixing a typo in the documentation you can prepend your commit with \[AIRFLOW-XXX\], code changes always need a Jira issue. ### Description The front page loads very slowly when the DB has latency because one blocking query is made per DAG against the DB. Even if we were to add indexes, the queries should still be batched to avoid an overhead of RTT * # of DAGs. The latest dagruns should be loaded asynchronously and in batch like the other UI elements that query the database. - [X] Here are some details about my PR, including screenshots of any UI changes: ### Tests - [X] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason: UI changes only. ### Commits - [X] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)": 1. Subject is separated from body by a blank line 1. Subject is limited to 50 characters (not including Jira issue reference) 1. Subject does not end with a period 1. Subject uses the imperative mood ("add", not "adding") 1. Body wraps at 72 characters 1. Body explains "what" and "why", not "how" ### Documentation - [X] In case of new functionality, my PR adds documentation that describes how to use it. - When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added. ### Code Quality - [X] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff` cc @ashb [ Full content available at: https://github.com/apache/incubator-airflow/pull/4005 ] This message was relayed via gitbox.apache.org for devnull@infra.apache.org
