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Merge "Add hacking guideline"

Jenkins authored on 2012/03/10 05:04:31
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HACKING.rst
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+Contributing to DevStack
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+========================
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+
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+
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+General
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+-------
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+
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+DevStack is written in POSIX shell script.  This choice was made because
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+it best illustrates the configuration steps that this implementation takes
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+on setting up and interacting with OpenStack components.  DevStack specifies
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+BASH and is compatible with Bash 3.
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+
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+DevStack's official repository is located on GitHub at
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+https://github.com/openstack-dev/devstack.git.  Besides the master branch that
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+tracks the OpenStack trunk branches a separate branch is maintained for all
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+OpenStack releases starting with Diablo (stable/diablo).
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+
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+The primary script in DevStack is ``stack.sh``, which performs the bulk of the
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+work for DevStack's use cases.  There is a subscript ``functions`` that contains
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+generally useful shell functions and is used by a number of the scripts in
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+DevStack.
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+
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+A number of additional scripts can be found in the ``tools`` directory that may
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+be useful in setting up special-case uses of DevStack. These include: bare metal
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+deployment, ramdisk deployment and Jenkins integration.
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+
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+
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+Scripts
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+-------
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+
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+DevStack scripts should generally begin by calling ``env(1)`` in the shebang line::
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+
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+    #!/usr/bin/env bash
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+
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+Sometimes the script needs to know the location of the DevStack install directory.
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+``TOP_DIR`` should always point there, even if the script itself is located in
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+a subdirectory::
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+
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+    # Keep track of the current devstack directory.
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+    TOP_DIR=$(cd $(dirname "$0") && pwd)
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+
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+Many scripts will utilize shared functions from the ``functions`` file.  There are
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+also rc files (``stackrc`` and ``openrc``) that are often included to set the primary
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+configuration of the user environment::
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+
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+    # Use openrc + stackrc + localrc for settings
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+    pushd $(cd $(dirname "$0")/.. && pwd) >/dev/null
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+
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+    # Import common functions
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+    source ./functions
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+
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+    # Import configuration
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+    source ./openrc
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+    popd >/dev/null
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+
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+``stack.sh`` is a rather large monolithic script that flows through from beginning
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+to end.  There is a proposal to segment it to put the OpenStack projects
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+into their own sub-scripts to better document the projects as a unit rather than
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+have it scattered throughout ``stack.sh``.  Someday.
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+
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+
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+Documentation
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+-------------
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+
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+The official DevStack repo on GitHub does not include a gh-pages branch that
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+GitHub uses to create static web sites.  That branch is maintained in the
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+`CloudBuilders DevStack repo`__ mirror that supports the
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+http://devstack.org site.  This is the primary DevStack
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+documentation along with the DevStack scripts themselves.
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+
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+__ repo_
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+.. _repo: https://github.com/cloudbuilders/devstack
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+
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+All of the scripts are processed with shocco_ to render them with the comments
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+as text describing the script below.  For this reason we tend to be a little
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+verbose in the comments _ABOVE_ the code they pertain to.  Shocco also supports
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+Markdown formatting in the comments; use it sparingly.  Specifically, ``stack.sh``
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+uses Markdown headers to divide the script into logical sections.
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+
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+.. _shocco: http://rtomayko.github.com/shocco/
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+
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+
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+Exercises
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+---------
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+
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+The scripts in the exercises directory are meant to 1) perform basic operational
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+checks on certain aspects of OpenStack; and b) document the use of the
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+OpenStack command-line clients.
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+
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+In addition to the guidelines above, exercise scripts MUST follow the structure
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+outlined here.  ``swift.sh`` is perhaps the clearest example of these guidelines.
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+These scripts are executed serially by ``exercise.sh`` in testing situations.
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+
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+* Begin and end with a banner that stands out in a sea of script logs to aid
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+  in debugging failures, particularly in automated testing situations.  If the
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+  end banner is not displayed, the script ended prematurely and can be assumed
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+  to have failed.
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+
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+  ::
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+
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+    echo "**************************************************"
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+    echo "Begin DevStack Exercise: $0"
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+    echo "**************************************************"
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+    ...
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+    set +o xtrace
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+    echo "**************************************************"
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+    echo "End DevStack Exercise: $0"
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+    echo "**************************************************"
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+
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+* The scripts will generally have the shell ``xtrace`` attribute set to display
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+  the actual commands being executed, and the ``errexit`` attribute set to exit
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+  the script on non-zero exit codes::
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+
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+    # This script exits on an error so that errors don't compound and you see
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+    # only the first error that occured.
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+    set -o errexit
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+
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+    # Print the commands being run so that we can see the command that triggers
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+    # an error.  It is also useful for following allowing as the install occurs.
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+    set -o xtrace
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+
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+* There are a couple of helper functions in the common ``functions`` sub-script
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+  that will check for non-zero exit codes and unset environment variables and
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+  print a message and exit the script.  These should be called after most client
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+  commands that are not otherwise checked to short-circuit long timeouts
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+  (instance boot failure, for example)::
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+
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+    swift post $CONTAINER
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+    die_if_error "Failure creating container $CONTAINER"
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+
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+    FLOATING_IP=`euca-allocate-address | cut -f2`
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+    die_if_not_set FLOATING_IP "Failure allocating floating IP"
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+
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+* The exercise scripts should only use the various OpenStack client binaries to
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+  interact with OpenStack.  This specifically excludes any ``*-manage`` tools
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+  as those assume direct access to configuration and databases, as well as direct
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+  database access from the exercise itself.
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+
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+* If specific configuration needs to be present for the exercise to complete,
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+  it should be staged in ``stack.sh``, or called from ``stack.sh`` (see
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+  ``files/keystone_data.sh`` for an example of this).
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+
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+* The ``OS_*`` environment variables should be the only ones used for all
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+  authentication to OpenStack clients as documented in the CLIAuth_ wiki page.
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+
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+.. _CLIAuth: http://wiki.openstack.org/CLIAuth
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+
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+* The exercise MUST clean up after itself if successful.  If it is not successful,
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+  it is assumed that state will be left behind; this allows a chance for developers
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+  to look around and attempt to debug the problem.  The exercise SHOULD clean up
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+  or graciously handle possible artifacts left over from previous runs if executed
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+  again.  It is acceptable to require a reboot or even a re-install of DevStack
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+  to restore a clean test environment.