Manually triggered dags should have default logical_date and run_after of "right now"

[dstandish]

Body

As part of the AIP-83 amendment process we decided to make logical_date nullable, and to make it default null for manually triggered dags.

We got some feedback that this will suck for users.

So we want to keep the airlfow 2 behavior where logical_date is now() by default, but the users can optionally select null.

NOTE: This will have a UI component!!!

We will need to update the UI date picker so that user can optionally choose null.

1. Manually triggering DAG Run via UI

• date picker will default to the time when modal opened
• user can null it out somehow
• bonus if there's a button to clear the date

2. Triggering Dag Run via API

• try to make it so if not supplied then it will be timezone.now() but if supplied we respect it. if this causes trouble and is more or less impossible to support (1), then we can keep it required

4. Trigger Dag Run Operator usage* if unset, it should take the logical date (yes, even if nullable) from the triggering dag run

• if set, respect it no matter what

Committer

• I acknowledge that I am a maintainer/committer of the Apache Airflow project.

[cmarteepants]

Three scenarios we need to account for are:

1. Manually triggering DAG Run via UI
2. Triggering Dag Run via API
3. Trigger Dag Run Operator usage

[dstandish]

@vatsrahul1001 talk to me / constance to confirm requirements i was going to review the slack thread again

[vatsrahul1001]

@dstandish / @cmarteepants Currently, logical_date is a required field in the API request; however, the user can pass it as null.

Do we want to make logical_date optional, defaulting to datetime.now() if not provided, while respecting any value explicitly passed?

Triggering Dag Run via API
try to make it so if not supplied then it will be timezone.now() but if supplied we respect it. if this causes trouble and is more or less impossible to support (1), then we can keep it required

[vatsrahul1001]

Currently, for TriggerDagRunOperator, logical_date defaults to None if not provided. Do we want to change this to datetime.now() as the default?

[cmarteepants]

Just started a lazy consensus vote: https://lists.apache.org/list.html?dev@airflow.apache.org