b2luigi
=======

``b2luigi`` — bringing batch 2 luigi!


``b2luigi`` is a helper package for ``luigi`` for scheduling large ``luigi`` workflows on a batch system.
It is as simple as

.. code-block:: python

    import b2luigi


    class MyTask(b2luigi.Task):
        def output(self):
            return b2luigi.LocalTarget("output_file.txt")

        def run(self):
            with self.output().open("w") as f:
                f.write("This is a test\n")


    if __name__ == "__main__":
        b2luigi.process(MyTask(), batch=True)

Jump right into it with out :ref:`quick-start-label`.

If you have never worked with ``luigi`` before, you may want to have a look into the `luigi documentation`_.
But you can learn most of the nice features also from this documentation!

.. attention::

    The API of ``b2luigi`` is still under construction.
    Please remember this when using the package in production!


Why not use the already created batch tasks?
--------------------------------------------

``luigi`` already contains a large set of tasks for scheduling and monitoring batch jobs [1]_.
But for thousands of tasks in very large projects with different task-defining libraries, you have some problems:

*   **You want to run many (many many!) batch jobs in parallel**
    In other ``luigi`` batch implementations, for every running batch job you also need a running task that monitors it.
    On most of the systems, the maximal number of processes is limited per user, so you will not be able to run more
    batch jobs than this.
    But what do you do if you have thousands of tasks to do?
*   **You have already a large set of luigi tasks in your project**
    In other implementations you either have to override a ``work`` function (and you are not allowed to touch
    the ``run`` function) or they can only run an external command, which you need to define.
    The first approach plays not well when mixing non-batch and batch task libraries and the second
    has problems when you need to pass complex arguments to the external command (via command line).
*   **You do not know which batch system you will run on**
    Currently, the batch tasks are mostly defined for a specific batch system. But what if you want to
    switch from AWS to Azure? From LSF to SGE?

Entering ``b2luigi``, which tries to solve all this (but was heavily inspired by the previous implementations):

*   You can run as many tasks as your batch system can handle in parallel! There will only be a single process running
    on your submission machine.
*   No need to rewrite your tasks! Just call them with ``b2luigi.process(.., batch=True)`` or with
    ``python file.py --batch`` and you are ready to go!
*   Switching the batch system is just a single change in a config file or one line in python.
    In the future, there will even be an automatic discovery of the batch system to use.


Is this the only thing I can do with ``b2luigi``?
-------------------------------------------------

As ``b2luigi`` should help you with large ``luigi`` projects, we have also included some helper functionalities for
``luigi`` tasks and task handling.
``b2luigi`` task is a super-hero version of ``luigi`` task, with simpler handling for output and input files.
Also, we give you working examples and best-practices for better data management and how to accomplish your goals,
that we have learned with time.


Why are you still talking, lets use it!
---------------------------------------

Have a look into the :ref:`quick-start-label`.

You can also start reading the :ref:`api-documentation-label` or the code on GitHub_.

If you find any bugs or want to improve the documentation, please send me a pull request.

This project is in beta. Please be extra cautious when using in production mode.
You can help me by working with one of the todo items described in :ref:`development-label`.

Content
-------

.. toctree::
    :maxdepth: 2

    usage/installation
    usage/quickstart
    usage/batch
    advanced/basf2-examples
    documentation/api
    documentation/run_modes
    advanced/faq
    advanced/development


The name
--------

``b2luigi`` stands for multiple things at the same time:

*   It brings **b**\ atch to (**2**\ ) ``luigi``.
*   It helps you with the **b**\ read and **b**\ utter work in ``luigi`` (e.g. proper data management)
*   It was developed for the `Belle II`_ experiment.


The team
--------

Current developer and maintainer
    The Belle II Collaboration (`belle2`_)

Original author
    Nils Braun (`nils-braun`_)

Former developer and maintainer
    Michael Eliachevitch (`meliache`_)

Features, fixing, help and testing
    * Felix Metzner (`FelixMetzner`_)
    * Patrick Ecker (`eckerpatrick`_)
    * Jochen Gemmler
    * Maximilian Welsch (`welschma`_)
    * Kilian Lieret (`klieret`_)
    * Sviatoslav Bilokin (`bilokin`_)
    * Phil Grace (`philiptgrace`_)
    * Anselm Baur (`anselmbaur`_)
    * Moritz Bauer (`sognetic`_)
    * Matthias Schnepf  (`mschnepf`_)
    * Artur Gottmann (`ArturAkh`_)
    * Caspar Schmitt (`schmitca`_)
    * Marcel Hohmann (`MarcelHoh`_)
    * Giacomo De Pietro (`GiacomoXT`_)
    * Alex Heidelbach (`AlexanderHeidelbach`_)
    * Tristan Fillinger (`0ctagon`_)
    * Jonas Eppelt (`JonasEppelt`_)

Stolen ideas
    * Implementation of SGE batch system (`sge`_).
    * Implementation of LSF batch system (`lsf`_).


.. _github: https://github.com/belle2/b2luigi
.. _`luigi documentation`: https://luigi.readthedocs.io/en/stable
.. _`Belle II`: https://www.belle2.org
.. _`belle2`: https://github.com/belle2
.. _`nils-braun`: https://github.com/nils-braun
.. _`meliache`: https://github.com/meliache
.. _`welschma`: https://github.com/welschma
.. _`FelixMetzner`: https://github.com/FelixMetzner
.. _`eckerpatrick`: https://github.com/eckerpatrick
.. _`klieret`: https://github.com/klieret
.. _`bilokin`: https://github.com/bilokin
.. _`philiptgrace`: https://github.com/philiptgrace
.. _`anselmbaur`: https://github.com/anselm-baur
.. _`sognetic`: https://github.com/sognetic
.. _`ArturAkh`: https://github.com/ArturAkh
.. _`mschnepf`: https://github.com/mschnepf
.. _`schmitca`: https://github.com/schmitca
.. _`MarcelHoh`: https://github.com/MarcelHoh
.. _`GiacomoXT`: https://github.com/GiacomoXT
.. _`AlexanderHeidelbach`: https://github.com/AlexanderHeidelbach
.. _`JonasEppelt`: https://github.com/JonasEppelt
.. _`0ctagon`: https://github.com/0ctagon
.. _`sge`: https://github.com/spotify/luigi/blob/master/luigi/contrib/sge.py
.. _`lsf`: https://github.com/spotify/luigi/pull/2373/files



.. [1] https://github.com/spotify/luigi/blob/master/luigi/contrib/sge.py