Invoking dbt as a module

[gouline]

Describe the feature

It would be nice to have a straightforward way of running dbt as a Python module.

To give some context, I use my own build tool https://github.com/gouline/molot that's written in Python and provides basic support for targets, dependencies and arguments. Something half way between Make and Gradle that helps with CI configuration. Things that can be done in Python (e.g. boto3, snowflake-connector-python) are done natively, everything else it just calls shell commands in a subprocess like a Makefile would.

So I'd like a way to invoke multiple dbt commands (e.g. run and docs generate) in one target by just importing dbt.main and calling a function multiple times. The way things are now, main() calls sys.exit(), which exists my outer build as well, and handle_and_check() requires raw command-line arguments passed manually as a list. Ideally, there should be a function of the form dbt.main.execute(command='run', profiles_dir=PROFILES_DIR, ...) that would execute a command and throw any exceptions for the caller to handle.

Describe alternatives you've considered

My current workaround is just invoking dbt command as a subprocess, but it seems like a backward way of doing it, considering that both are Python applications.

Additional context

Closest thing I could find on the issue tracker was #1488, but that sounds more complex than what I'm proposing.

Who will this benefit?

This would benefit anyone who orchestrates their builds with Python scripts.

[drewbanin]

Hey @gouline - kind of funny we didn't already have an issue for this one :)

We've kicked around the idea of providing a public API for dbt in Python a couple of times now. I'm happy for us to add a public method like dbt.main.execute(command='run', profiles_dir=PROFILES_DIR, ...) which implements logic similar to handle_and_check.

I'd still like to provide a rich Python-based interface for running dbt projects in the future. I think that would entail model selection, configuration, execution, etc, etc. In this case though, I think a top-level method like execute (or similar) gets us moving in the right direction.

Thanks for raising this!

[Dandandan]

Hello I like to help out on this issue.
Any pointers on how this should be implemented?

Should it just pass on the args to the parser?

[picousse]

This one is pretty old.
Is there any progress on this?

Is there something I/we could help with?

[mik-laj]

sys.exit() raises SystemExit exception, so we can use a try-except statement to handle this situation.
Here is example;
https://github.com/apache/airflow/blob/8505d2f0a4524313e3eff7a4f16b9a9439c7a79f/airflow/cli/commands/config_command.py#L40-L44
https://github.com/apache/airflow/blob/8505d2f0a4524313e3eff7a4f16b9a9439c7a79f/tests/cli/commands/test_config_command.py#L60-L80

To catch stdout/stderr, we can use contextlib.redirect_stdout/contextlib.redirect_stderr decorator.

with contextlib.redirect_stdout(io.StringIO()) as temp_stdout:
    __import__('dbt.main').main(argv)

[ismailsimsek]

+1 Is there any progress on this?

[WillemSFV]

+1 Is there any progress on this?

I suspect there won't be much progress on this now that DBT Cloud's a thing.

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[github-actions]

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[ismailsimsek]

Hello I like to help out on this issue. Any pointers on how this should be implemented?

Should it just pass on the args to the parser?

+1

[jtcohen6]

This is a fairly old issue. We are finally making progress in this direction, providing a programmatic API into dbt Core: #5527

The ability to invoke dbt as a module (instead of CLI script) isn't explicitly in scope for that initiative, but the big idea— providing a more sensible "main" method as entry-point to Core execution—certainly is.

[manugarri]

any updates on this? Seems like it would be easy to implement given how all of dbt-core is python already.

[jtcohen6]

@manugarri Check out:

• [CT-1581] [Epic] dbt-core as a library: first steps #6356
• [CT-1602] [Feature] a thin layer for calling dbt top level commands programatically #6381
• [CT-1770] [Feature] [Spike] Review programmatic entry point for top-level commands #6550

[joellabes]

This issue has better google results than the actual feature's docs, so I'm going to leave a pointer here: https://docs.getdbt.com/reference/programmatic-invocations