Triggerer Process Do Not create new trigger instance to run

[Greetlist]

Apache Airflow version

2.2.1

What happened

When a Deferrable Task which is cleared or generated. This Trigger's TriggererId is NULL,and never change, which cause this trigger is never init and run by triggerer process.

What you expected to happen

When a Deferrable Task is generated, It will init and run correctly.

How to reproduce

Clear a Deferrable Task.
I add some log to source code and find out the reason of this problem:

First Query:
is None has a strange behavior, It does not work.
Second Query:
when the trigerer_id has a NULL value in database, it can not query correctly.

I fix both problems by:

Operating System

Ubuntu 16.04

Versions of Apache Airflow Providers

No response

Deployment

Other

Deployment details

1.One Triggerer Process
2. Three Scheduler
3. Pecona Mysql 8.0

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[potiuk]

Assigned you to it @Greetlist - can you please make a PR for that one with "Fixes: #21005" in the message (and cc: @andrewgodwin best to review it ), I thin you wil have to add a test case for that one but we can guide you.

[Greetlist]

I'm willing to make a PR for it, but I don't know how to add a test case. By the way, there is a test_trigger.py file in tests, Can I just use the file to test this case?

[potiuk]

I believe so - but do not know too much about it - I think you can start with PR even without tests and the right people will comment there on how to add tests!

[Greetlist]

I have another PR #19640 which has not been Merged yet.I should wait until it is finished so I can start a new PR for this.