:title: Installation

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

Nodepool consists of a long-running daemon which uses ZooKeeper
for coordination with Zuul.

External Requirements
---------------------

ZooKeeper
~~~~~~~~~

Nodepool uses ZooKeeper to coordinate image builds with its separate
image builder component.  A single ZooKeeper instance running on the
Nodepool server is fine.  Larger installations may wish to use a
multi-node ZooKeeper installation, in which case three nodes are
usually recommended.

Nodepool only needs to be told how to contact the ZooKeeper cluster;
it will automatically populate the ZNode structure as needed.

Statsd and Graphite
~~~~~~~~~~~~~~~~~~~

If you have a Graphite system with ``statsd``, Nodepool can be
configured to send information to it.  Set the environment variable
``STATSD_HOST`` to the ``statsd`` hostname (and optionally
``STATSD_PORT`` if this should be different to the default ``8125``)
for the Nodepool daemon to enable this support.

Install Nodepool
----------------

Install Nodepool prerequisites.

Nodepool requires Python 3.5 or newer.

RHEL 7 / CentOS 7::

  yum install libffi libffi-devel @development python python-devel

You may install Nodepool directly from PyPI with pip::

  pip install nodepool

Or install directly from a git checkout with::

  pip install .

Configuration
-------------

Nodepool has one required configuration file, which defaults to
``/etc/nodepool/nodepool.yaml``. This can be changed with the ``-c`` option.
The Nodepool configuration file is described in :ref:`configuration`.

There is support for a secure file that is used to store nodepool
configurations that contain sensitive data. It currently only supports
specifying ZooKeeper credentials. If ZooKeeper credentials are defined in
both configuration files, the data in the secure file takes precedence.
The secure file location can be changed with the ``-s`` option and follows
the same file format as the Nodepool configuration file.

There is an optional logging configuration file, specified with the ``-l``
option. The logging configuration file can accept either:

* the traditional ini python logging `configuration file format
  <https://docs.python.org/2/library/logging.config.html#configuration-file-format>`_.

* a `.yml` or `.yaml` suffixed file that will be parsed and loaded as the newer
  `dictConfig format
  <https://docs.python.org/2/library/logging.config.html#configuration-dictionary-schema>`_.

The Nodepool configuration file is described in :ref:`configuration`.