.. _chapter_developers:

***********************
Developer Documentation
***********************

Installation from Source
========================

If you are planning to contribute to the RADICAL-Pilot codebase, or if you
want to use the latest and greatest development features, you can download and
install RADICAL-Pilot directly from the source code.

First, you need to check out the source code from GitHub.

.. code-block:: bash

    git clone https://github.com/radical-cybertools/radical.pilot.git

Next, set up a virtualenv and run the installer directly from the root
directory of the repository you just cloned:

.. code-block:: bash

    pip install --upgrade .


License
=======

RADICAL-Pilot uses the MIT License
(https://github.com/radical-cybertools/radical.pilot/blob/devel/LICENSE.md).


Style Guide
===========

To maintain consistency and uniformity we request people to follow our coding
style guidelines.

We generally follow PEP 8 (http://legacy.python.org/dev/peps/pep-0008/), with
one explicit exception:

  - When alignment of assignments improves readability.


Debugging
=========

The `RADICAL_PILOT_LOG_LVL` environment variable controls the debug output of
a RADICAL-Pilot application. Possible values are:

  * `DEBUG`
  * `INFO`
  * `WARNING`
  * `ERROR`
  * `CRITICAL`

The environment variable `RADICAL_LOG_LVL` controls the log output from the
lower levels of the software stack.  The variable `RADICAL_LOG_TGT` and
`RADICAL_PILOT_LOG_TGT` can be used to specify a filename in which the log
messages will be stored (default target is STDERR).


RADICAL-Pilot Architecture
==========================

RADICAL-Pilot is a distributed system that executes both a client and an agent
component. The client component executes on the same machine and the same
Python interpreter on which the application written against the RADICAL-Pilot
API executes. The agent executes either locally into a separate Python
interpreter or, most often, on a remote HPC machine into a dedicated Python
interpreter.


PilotManager and PilotManager Worker
------------------------------------

.. image:: images/architecture_pilotmanager.png

Download :download:`PDF version <images/architecture_pilotmanager.pdf>`.

TaskManager and TaskManager Worker
----------------------------------

.. image:: images/architecture_taskmanager.png

Download :download:`PDF version <images/architecture_taskmanager.pdf>`.