Persist start/end date and duration for DummyOperator Task Instance

[XD-DENG]

This PR is to address issue #8662

Currently, task instances of DummyOperators are always marked as SUCCESS then immediately being skipped. Other entries like start_date, end_date, and duration are not marked for it in the database (in task_instance table in DB, start_date, end_date, and duration are all NULL for DummyOperator tasks).

One of the issues resulted from this is that when we hover over task instances of DummyOperator in RBAC UI, the started and ended times are always showing the CURRENT time, instead of the the actual task started and ended time (like other operators/sensors).

For details, please refer to #8662

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[ashb]

Sounds like there's also a bug in the UI code - I would have expected it to show nothing rather than current time

[XD-DENG]

Hi @ashb , IMO as a user it's good to know when this DummyOperator task is processed by the scheduler, so showing the start/end time for DummyOperator tasks in UI is useful

[ashb]

Oh yes absolutely.

I just meant cos of the bug with the missing fields I would have expected the UI to show nothing.

[XD-DENG]

Oh yes absolutely.

I just meant cos of the bug with the missing fields I would have expected the UI to show nothing.

Ha, get what you mean. That's exactly the behaviour in the non-RBAC UI.

[XD-DENG]

@ashb you are right that the UI JS code is handling this correctly,

airflow/airflow/www_rbac/static/js/task-instances.js

Line 32 in a943d6b

function generateTooltipDateTimes(startDate, endDate, dagTZ) {

and

airflow/airflow/www_rbac/static/js/task-instances.js

Line 86 in a943d6b

tt += generateTooltipDateTimes(ti.start_date, ti.end_date, dagTZ); // dagTZ has been defined in dag.html

assumes that ti.start_date and ti.end_date are always available. While they are none, it falls back to "default" value which is current time.

However I assume this is no longer an issue/bug if this PR is merged?

[ashb]

Probably worth another pr to fix that.

(This was a bug I introduced in my UI tz work - moment.utc(unrefined) returns now, we didn't used to call moment at all.)

[XD-DENG]

Hi @kaxil mind taking a look when you have time? Need to merge this before I proceed to merge #8667 (which has been approved already). Thanks :)