======
hupper
======

``hupper`` is monitor for your Python process. When files change, the process
will be restarted. It can be extended to watch arbitrary files. Reloads can
also be triggered manually from code.

Builtin file monitors (in order of preference):

- :ref:`watchman_support`

- :ref:`watchdog_support`

- :ref:`polling_support`

Installation
============

Stable release
--------------

To install hupper, run this command in your terminal:

.. code-block:: console

    $ pip install hupper

If you don't have `pip`_ installed, this `Python installation guide`_ can guide
you through the process.

.. _pip: https://pip.pypa.io
.. _Python installation guide: http://docs.python-guide.org/en/latest/starting/installation/


From sources
------------

The sources for hupper can be downloaded from the `Github repo`_.

.. code-block:: console

    $ git clone https://github.com/Pylons/hupper.git

Once you have a copy of the source, you can install it with:

.. code-block:: console

    $ pip install -e .

.. _Github repo: https://github.com/Pylons/hupper

Builtin File Monitors
=====================

.. _watchman_support:

Watchman
--------

If the `watchman <https://facebook.github.io/watchman/>`_ daemon is running,
it is the preferred mechanism for monitoring files.

On MacOS it can be installed via:

.. code-block:: console

    $ brew install watchman

Implementation: :class:`hupper.watchman.WatchmanFileMonitor`

.. _watchdog_support:

Watchdog
--------

If `watchdog <https://pypi.org/project/watchdog/>`_ is installed, it will be
used to more efficiently watch for changes to files.

.. code-block:: console

    $ pip install watchdog

This is an optional dependency and if it's not installed, then ``hupper`` will
fallback to less efficient polling of the filesystem.

Implementation: :class:`hupper.watchdog.WatchdogFileMonitor`

.. _polling_support:

Polling
-------

The least efficient but most portable approach is to use basic file polling.

The ``reload_interval`` parameter controls how often the filesystem is scanned
and defaults to once per second.

Implementation: :class:`hupper.polling.PollingFileMonitor`

Command-line Usage
==================

Hupper can load any Python code similar to ``python -m <module>`` by using the
``hupper -m <module>`` program.

.. code-block:: console

   $ hupper -m myapp
   Starting monitor for PID 23982.

API Usage
=========

The reloading mechanism is implemented by forking worker processes from a
parent monitor. Start by defining an entry point for your process. This must
be an importable path in string format. For example,
``myapp.scripts.serve.main``:

.. code-block:: python

    # myapp/scripts/serve.py

    import sys
    import hupper
    import waitress

    def wsgi_app(environ, start_response):
        start_response('200 OK', [('Content-Type', 'text/plain'])
        yield [b'hello']

    def main(args=sys.argv[1:]):
        if '--reload' in args:
            # start_reloader will only return in a monitored subprocess
            reloader = hupper.start_reloader('myapp.scripts.serve.main')

            # monitor an extra file
            reloader.watch_files(['foo.ini'])

        waitress.serve(wsgi_app)

Many applications will tend to re-use the same startup code for both the
monitor and the worker. As a convenience to support this use case, the
:func:`hupper.start_reloader` function can be invoked both from the parent
process as well as the worker. When called initially from the parent process,
it will fork a new worker, then start the monitor and never return. When
called from the worker process it will return a proxy object that can be used
to communicate back to the monitor.

Checking if the reloader is active
----------------------------------

:func:`hupper.is_active` will return ``True`` if the reloader is active and
the current process may be reloaded.

Controlling the monitor
-----------------------

The worker processes may communicate back to the monitor and notify it of
new files to watch. This can be done by acquiring a reference to the
:class:`hupper.interfaces.IReloaderProxy` instance living in the worker
process. The :func:`hupper.start_reloader` function will return the instance
or :func:`hupper.get_reloader` can be used as well.

Overriding the default file monitor
-----------------------------------

.. versionadded:: 1.2

By default, ``hupper`` will auto-select the best file monitor based on what
is available. The preferred order is ``watchdog`` then ``polling``. If
``watchdog`` is installed but you do not want to use it for any reason, you
may override the default by specifying the monitor you wish to use instead in
the ``HUPPER_DEFAULT_MONITOR`` environment variable. For example:

.. code:: bash

   $ HUPPER_DEFAULT_MONITOR=hupper.polling.PollingFileMonitor hupper -m foo

More Information
================

.. toctree::
   :maxdepth: 1

   api
   contributing
   changes

Indices and tables
==================

* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`