Contributing to DevStack
 ========================
 
 
 General
 -------
 

 DevStack is written in UNIX shell script.  It uses a number of bash-isms
 and so is limited to Bash (version 3 and up) and compatible shells.
 Shell script was chosen because it best illustrates the steps used to
 set up and interact with OpenStack components.

 
 DevStack's official repository is located on GitHub at
 https://github.com/openstack-dev/devstack.git.  Besides the master branch that
 tracks the OpenStack trunk branches a separate branch is maintained for all
 OpenStack releases starting with Diablo (stable/diablo).
 

 Contributing code to DevStack follows the usual OpenStack process as described
 in `How To Contribute`__ in the OpenStack wiki.  `DevStack's LaunchPad project`__
 contains the usual links for blueprints, bugs, tec.
 
 __ contribute_
 .. _contribute: http://wiki.openstack.org/HowToContribute.
 
 __ lp_
 .. _lp: https://launchpad.net/~devstack
 

 The primary script in DevStack is ``stack.sh``, which performs the bulk of the
 work for DevStack's use cases.  There is a subscript ``functions`` that contains
 generally useful shell functions and is used by a number of the scripts in
 DevStack.
 

 The ``lib`` directory contains sub-scripts for projects or packages that ``stack.sh``
 sources to perform much of the work related to those projects.  These sub-scripts
 contain configuration defaults and functions to configure, start and stop the project
 or package.  These variables and functions are also used by related projects,
 such as Grenade, to manage a DevStack installation.
 

 A number of additional scripts can be found in the ``tools`` directory that may

 be useful in supporting DevStack installations.  Of particular note are ``info.sh``

 to collect and report information about the installed system, and ``install_prereqs.sh``

 that handles installation of the prerequisite packages for DevStack.  It is
 suitable, for example, to pre-load a system for making a snapshot.

 
 
 Scripts
 -------
 
 DevStack scripts should generally begin by calling ``env(1)`` in the shebang line::
 
     #!/usr/bin/env bash
 
 Sometimes the script needs to know the location of the DevStack install directory.
 ``TOP_DIR`` should always point there, even if the script itself is located in
 a subdirectory::
 

     # Keep track of the current DevStack directory.

     TOP_DIR=$(cd $(dirname "$0") && pwd)
 
 Many scripts will utilize shared functions from the ``functions`` file.  There are
 also rc files (``stackrc`` and ``openrc``) that are often included to set the primary
 configuration of the user environment::
 

     # Keep track of the current DevStack directory.

     TOP_DIR=$(cd $(dirname "$0") && pwd)

 
     # Import common functions

     source $TOP_DIR/functions

 
     # Import configuration

     source $TOP_DIR/openrc

 
 ``stack.sh`` is a rather large monolithic script that flows through from beginning

 to end.  It has been broken down into project-specific subscripts (as noted above)
 located in ``lib`` to make ``stack.sh`` more manageable and to promote code reuse.

 
 These library sub-scripts have a number of fixed entry points, some of which may
 just be stubs.  These entry points will be called by ``stack.sh`` in the
 following order::
 
     install_XXXX
     configure_XXXX
     init_XXXX
     start_XXXX
     stop_XXXX
     cleanup_XXXX
 
 There is a sub-script template in ``lib/templates`` to be used in creating new
 service sub-scripts.  The comments in ``<>`` are meta comments describing
 how to use the template and should be removed.

 In order to show the dependencies and conditions under which project functions
 are executed the top-level conditional testing for things like ``is_service_enabled``
 should be done in ``stack.sh``.  There may be nested conditionals that need
 to be in the sub-script, such as testing for keystone being enabled in
 ``configure_swift()``.
 

 stackrc
 -------
 
 ``stackrc`` is the global configuration file for DevStack.  It is responsible for

 calling ``local.conf`` (or ``localrc`` if it exists) so local user configuration
 is recognized.

 
 The criteria for what belongs in ``stackrc`` can be vaguely summarized as
 follows:
 

 * All project repositories and branches handled directly in ``stack.sh``
 * Global configuration that may be referenced in ``local.conf``, i.e. ``DEST``, ``DATA_DIR``

 * Global service configuration like ``ENABLED_SERVICES``
 * Variables used by multiple services that do not have a clear owner, i.e.
   ``VOLUME_BACKING_FILE_SIZE`` (nova-volumes and cinder) or ``PUBLIC_NETWORK_NAME``

   (nova-network and neutron)

 * Variables that can not be cleanly declared in a project file due to
   dependency ordering, i.e. the order of sourcing the project files can
   not be changed for other reasons but the earlier file needs to dereference a
   variable set in the later file.  This should be rare.
 

 Also, variable declarations in ``stackrc`` before ``local.conf`` is sourced
 do NOT allow overriding (the form
 ``FOO=${FOO:-baz}``); if they did then they can already be changed in ``local.conf``

 and can stay in the project file.
 

 Documentation
 -------------
 
 The official DevStack repo on GitHub does not include a gh-pages branch that
 GitHub uses to create static web sites.  That branch is maintained in the
 `CloudBuilders DevStack repo`__ mirror that supports the
 http://devstack.org site.  This is the primary DevStack
 documentation along with the DevStack scripts themselves.
 
 __ repo_
 .. _repo: https://github.com/cloudbuilders/devstack
 
 All of the scripts are processed with shocco_ to render them with the comments
 as text describing the script below.  For this reason we tend to be a little
 verbose in the comments _ABOVE_ the code they pertain to.  Shocco also supports
 Markdown formatting in the comments; use it sparingly.  Specifically, ``stack.sh``
 uses Markdown headers to divide the script into logical sections.
 

 .. _shocco: https://github.com/dtroyer/shocco/tree/rst_support
 
 The script used to drive <code>shocco</code> is <code>tools/build_docs.sh</code>.

 
 
 Exercises
 ---------
 
 The scripts in the exercises directory are meant to 1) perform basic operational
 checks on certain aspects of OpenStack; and b) document the use of the
 OpenStack command-line clients.
 
 In addition to the guidelines above, exercise scripts MUST follow the structure
 outlined here.  ``swift.sh`` is perhaps the clearest example of these guidelines.
 These scripts are executed serially by ``exercise.sh`` in testing situations.
 
 * Begin and end with a banner that stands out in a sea of script logs to aid
   in debugging failures, particularly in automated testing situations.  If the
   end banner is not displayed, the script ended prematurely and can be assumed
   to have failed.
 
   ::
 
     echo "**************************************************"
     echo "Begin DevStack Exercise: $0"
     echo "**************************************************"
     ...
     set +o xtrace
     echo "**************************************************"
     echo "End DevStack Exercise: $0"
     echo "**************************************************"
 
 * The scripts will generally have the shell ``xtrace`` attribute set to display
   the actual commands being executed, and the ``errexit`` attribute set to exit
   the script on non-zero exit codes::
 
     # This script exits on an error so that errors don't compound and you see

     # only the first error that occurred.

     set -o errexit
 
     # Print the commands being run so that we can see the command that triggers
     # an error.  It is also useful for following allowing as the install occurs.
     set -o xtrace
 

 * Settings and configuration are stored in ``exerciserc``, which must be
   sourced after ``openrc`` or ``stackrc``::
 
     # Import exercise configuration
     source $TOP_DIR/exerciserc
 

 * There are a couple of helper functions in the common ``functions`` sub-script
   that will check for non-zero exit codes and unset environment variables and
   print a message and exit the script.  These should be called after most client
   commands that are not otherwise checked to short-circuit long timeouts
   (instance boot failure, for example)::
 
     swift post $CONTAINER
     die_if_error "Failure creating container $CONTAINER"
 
     FLOATING_IP=`euca-allocate-address | cut -f2`
     die_if_not_set FLOATING_IP "Failure allocating floating IP"
 

 * If you want an exercise to be skipped when for example a service wasn't
   enabled for the exercise to be run, you can exit your exercise with the
   special exitcode 55 and it will be detected as skipped.
 

 * The exercise scripts should only use the various OpenStack client binaries to
   interact with OpenStack.  This specifically excludes any ``*-manage`` tools
   as those assume direct access to configuration and databases, as well as direct
   database access from the exercise itself.
 
 * If specific configuration needs to be present for the exercise to complete,
   it should be staged in ``stack.sh``, or called from ``stack.sh`` (see
   ``files/keystone_data.sh`` for an example of this).
 
 * The ``OS_*`` environment variables should be the only ones used for all
   authentication to OpenStack clients as documented in the CLIAuth_ wiki page.
 
 .. _CLIAuth: http://wiki.openstack.org/CLIAuth
 
 * The exercise MUST clean up after itself if successful.  If it is not successful,
   it is assumed that state will be left behind; this allows a chance for developers
   to look around and attempt to debug the problem.  The exercise SHOULD clean up
   or graciously handle possible artifacts left over from previous runs if executed
   again.  It is acceptable to require a reboot or even a re-install of DevStack
   to restore a clean test environment.