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Setting Up and Using a Development Environment

This page describes how to setup and use a working Python development environment that can be used in developing nova on Ubuntu, Fedora or Mac OS X. These instructions assume you're already familiar with git.

Following these instructions will allow you to build the documentation and run the nova unit tests. If you want to be able to run nova (i.e., launch VM instances), you will also need to --- either manually or by letting DevStack do it for you --- install libvirt and at least one of the supported hypervisors. Running nova is currently only supported on Linux, although you can run the unit tests on Mac OS X.

Setup

There are two ways to create a development environment: using DevStack, or explicitly installing and cloning just what you need.

Using DevStack

The easiest way to build a fully functional development environment is with DevStack. DevStack will hack your machine pretty hard, and so we recommend that you create a machine (such as a VM or Vagrant box) running a distribution supported by DevStack and run DevStack there. For example, there is a Vagrant script for DevStack at http://git.openstack.org/cgit/openstack-dev/devstack-vagrant/ .

Include the line

INSTALL_TESTONLY_PACKAGES=True

in the localrc file you use to control DevStack. This will cause DevStack to install what you need for testing and documentation building as well as running the system.

Explicit Install/Clone

DevStack installs a complete OpenStack environment. Alternatively, you can explicitly install and clone just what you need for Nova development.

The first step of this process is to install the system (not Python) packages that are required. Following are instructions on how to do this on Linux and on the Mac.

Linux Systems

Note

This section is tested for Nova on Ubuntu (14.04-64) and Fedora-based (RHEL 6.1) distributions. Feel free to add notes and change according to your experiences or operating system.

Install the prerequisite packages.

On Ubuntu:

sudo apt-get install python-dev libssl-dev python-pip git-core libxml2-dev libxslt-dev pkg-config libffi-dev libpq-dev libmysqlclient-dev libvirt-dev graphviz libsqlite3-dev python-tox

On Ubuntu Precise (12.04) you may also need to add the following packages:

sudo apt-get build-dep python-mysqldb
# enable cloud-archive to get the latest libvirt
sudo apt-get install python-software-properties
sudo add-apt-repository cloud-archive:icehouse
sudo apt-get install libvirt-dev

On Fedora-based distributions (e.g., Fedora/RHEL/CentOS/Scientific Linux):

sudo yum install python-devel openssl-devel python-pip git gcc libxslt-devel mysql-devel postgresql-devel libffi-devel libvirt-devel graphviz sqlite-devel
sudo pip-python install tox

On openSUSE-based distributions (SLES 12, openSUSE 13.1, Factory or Tumbleweed):

sudo zypper in gcc git libffi-devel libmysqlclient-devel libvirt-devel libxslt-devel postgresql-devel python-devel python-pip python-tox python-virtualenv

Mac OS X Systems

Install virtualenv:

sudo easy_install virtualenv

Check the version of OpenSSL you have installed:

openssl version

The stock version of OpenSSL that ships with Mac OS X 10.6 (OpenSSL 0.9.8l) or Mac OS X 10.7 (OpenSSL 0.9.8r) or Mac OS X 10.10.3 (OpenSSL 0.9.8zc) works fine with nova. OpenSSL versions from brew like OpenSSL 1.0.1k work fine as well.

Getting the code

Once you have the prerequisite system packages installed, the next step is to clone the code.

Grab the code from git:

git clone https://git.openstack.org/openstack/nova
cd nova

Building the Documentation

To do a full documentation build, issue the following command while the nova directory is current.

tox -edocs

That will create a Python virtual environment, install the needed Python prerequisites in that environment, and build all the documentation in that environment.

The following variant will do the first two steps but not build any documentation.

tox --notest -edocs

The virtual environment built by tox for documentation building will be found in .tox/docs. You can enter that virtual environment in the usual way, as follows.

source .tox/docs/bin/activate

To build just the man pages, enter that virtual environment and issue the following command while the nova directory is current.

python setup.py build_sphinx -b man

After building the man pages, they can be found in doc/build/man/. A sufficiently authorized user can install the man page onto the system by following steps like the following, which are for the nova-scheduler man page.

mkdir /usr/local/man/man1
install -g 0 -o 0 -m 0644 doc/build/man/nova-scheduler.1  /usr/local/man/man1/nova-scheduler.1
gzip /usr/local/man/man1/nova-scheduler.1
man nova-scheduler

Running unit tests

See unit_tests for details.

Using a remote debugger

Some modern IDE such as pycharm (commercial) or Eclipse (open source) support remote debugging. In order to run nova with remote debugging, start the nova process with the following parameters --remote_debug-host <host IP where the debugger is running> --remote_debug-port <port it is listening on>

Before you start your nova process, start the remote debugger using the instructions for that debugger. For pycharm - http://blog.jetbrains.com/pycharm/2010/12/python-remote-debug-with-pycharm/ For Eclipse - http://pydev.org/manual_adv_remote_debugger.html

More detailed instructions are located here - http://novaremotedebug.blogspot.com

Using fake computes for tests

The number of instances supported by fake computes is not limited by physical constraints. It allows you to perform stress tests on a deployment with few resources (typically a laptop). But you must avoid using scheduler filters limiting the number of instances per compute (like RamFilter, DiskFilter, AggregateCoreFilter), otherwise they will limit the number of instances per compute.

Fake computes can also be used in multi hypervisor-type deployments in order to take advantage of fake and "real" computes during tests:

  • create many fake instances for stress tests
  • create some "real" instances for functional tests

Fake computes can be used for testing Nova itself but also applications on top of it.

Contributing Your Work

Once your work is complete you may wish to contribute it to the project. Refer to HowToContribute for information. Nova uses the Gerrit code review system. For information on how to submit your branch to Gerrit, see GerritWorkflow.