xuganyu96 commented on issue #31818:
URL: https://github.com/apache/airflow/issues/31818#issuecomment-1585827854
# How database check is performed
The `airflow.cli.commands.db_command.check` function calls the function
`airflow.utils.db.check`, which in turns uses the provided session to execute a
trivial SQL command:
```python
@provide_session
def check(session: Session = NEW_SESSION):
"""
Checks if the database works.
:param session: session of the sqlalchemy
"""
session.execute(text("select 1 as is_alive;"))
log.info("Connection successful.")
```
The DB check command will let the `execute` function call raise unhandled
exception as a "fail".
For implementing retry, one approach would be to catch the exception raised
by `execute` each time and update the retry status in the "except" clause.
Note that `airflow.utils.db.check` is not used anywhere else, so it is also
possible to refactor `db.check` in a major way, such as letting it return a
boolean indicating whether the check is successful, which avoids using (what I
think to be rather unsavory) try-catch blocks and makes the logic more straight
forward, but oh well.
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