======= Plugins ======= DevStack has a couple of plugin mechanisms to allow easily adding support for additional projects and features. Extras.d Hooks ============== These hooks are an extension of the service calls in ``stack.sh`` at specific points in its run, plus ``unstack.sh`` and ``clean.sh``. A number of the higher-layer projects are implemented in DevStack using this mechanism. The script in ``extras.d`` is expected to be mostly a dispatcher to functions in a ``lib/*`` script. The scripts are named with a zero-padded two digits sequence number prefix to control the order that the scripts are called, and with a suffix of ``.sh``. DevStack reserves for itself the sequence numbers 00 through 09 and 90 through 99. Below is a template that shows handlers for the possible command-line arguments: :: # template.sh - DevStack extras.d dispatch script template # check for service enabled if is_service_enabled template; then if [[ "$1" == "source" ]]; then # Initial source of lib script source $TOP_DIR/lib/template fi if [[ "$1" == "stack" && "$2" == "pre-install" ]]; then # Set up system services echo_summary "Configuring system services Template" install_package cowsay elif [[ "$1" == "stack" && "$2" == "install" ]]; then # Perform installation of service source echo_summary "Installing Template" install_template elif [[ "$1" == "stack" && "$2" == "post-config" ]]; then # Configure after the other layer 1 and 2 services have been configured echo_summary "Configuring Template" configure_template elif [[ "$1" == "stack" && "$2" == "extra" ]]; then # Initialize and start the template service echo_summary "Initializing Template" ##init_template fi if [[ "$1" == "unstack" ]]; then # Shut down template services # no-op : fi if [[ "$1" == "clean" ]]; then # Remove state and transient data # Remember clean.sh first calls unstack.sh # no-op : fi fi The arguments are: - **source** - Called by each script that utilizes ``extras.d`` hooks; this replaces directly sourcing the ``lib/*`` script. - **stack** - Called by ``stack.sh`` three times for different phases of its run: - **pre-install** - Called after system (OS) setup is complete and before project source is installed. - **install** - Called after the layer 1 and 2 projects source and their dependencies have been installed. - **post-config** - Called after the layer 1 and 2 services have been configured. All configuration files for enabled services should exist at this point. - **extra** - Called near the end after layer 1 and 2 services have been started. This is the existing hook and has not otherwise changed. - **unstack** - Called by ``unstack.sh`` before other services are shut down. - **clean** - Called by ``clean.sh`` before other services are cleaned, but after ``unstack.sh`` has been called. Externally Hosted Plugins ========================= Based on the extras.d hooks, DevStack supports a standard mechansim for including plugins from external repositories. The plugin interface assumes the following: An external git repository that includes a ``devstack/`` top level directory. Inside this directory there can be 2 files. - ``settings`` - a file containing global variables that will be sourced very early in the process. This is helpful if other plugins might depend on this one, and need access to global variables to do their work. Your settings should include any ``enable_service`` lines required by your plugin. This is especially important if you are kicking off services using ``run_process`` as it only works with enabled services. Be careful to allow users to override global-variables for customizing their environment. Usually it is best to provide a default value only if the variable is unset or empty; e.g. in bash syntax ``FOO=${FOO:-default}``. - ``plugin.sh`` - the actual plugin. It will be executed by devstack during it's run. The run order will be done in the registration order for these plugins, and will occur immediately after all in tree extras.d dispatch at the phase in question. The plugin.sh looks like the extras.d dispatcher above. Plugins are registered by adding the following to the localrc section of ``local.conf``. They are added in the following format:: [[local|localrc]] enable_plugin [GITREF] - ``name`` - an arbitrary name. (ex: glustfs, docker, zaqar, congress) - ``giturl`` - a valid git url that can be cloned - ``gitref`` - an optional git ref (branch / ref / tag) that will be cloned. Defaults to master. An example would be as follows:: enable_plugin ec2api git://git.openstack.org/stackforge/ec2api Plugins for gate jobs --------------------- All OpenStack plugins that wish to be used as gate jobs need to exist in OpenStack's gerrit. Both ``openstack`` namespace and ``stackforge`` namespace are fine. This allows testing of the plugin as well as provides network isolation against upstream git repository failures (which we see often enough to be an issue). Ideally plugins will be implemented as ``devstack`` directory inside the project they are testing. For example, the stackforge/ec2-api project has it's pluggin support in it's tree. In the cases where there is no "project tree" per say (like integrating a backend storage configuration such as ceph or glusterfs) it's also allowed to build a dedicated ``stackforge/devstack-plugin-FOO`` project to house the plugin. Note jobs must not require cloning of repositories during tests. Tests must list their repository in the ``PROJECTS`` variable for `devstack-gate `_ for the repository to be available to the test. Further information is provided in the project creator's guide. Hypervisor ========== Hypervisor plugins are fairly new and condense most hypervisor configuration into one place. The initial plugin implemented was for Docker support and is a useful template for the required support. Plugins are placed in ``lib/nova_plugins`` and named ``hypervisor-`` where ```` is the value of ``VIRT_DRIVER``. Plugins must define the following functions: - ``install_nova_hypervisor`` - install any external requirements - ``configure_nova_hypervisor`` - make configuration changes, including those to other services - ``start_nova_hypervisor`` - start any external services - ``stop_nova_hypervisor`` - stop any external services - ``cleanup_nova_hypervisor`` - remove transient data and cache System Packages =============== Devstack provides a framework for getting packages installed at an early phase of its execution. This packages may be defined in a plugin as files that contain new-line separated lists of packages required by the plugin Supported packaging systems include apt and yum across multiple distributions. To enable a plugin to hook into this and install package dependencies, packages may be listed at the following locations in the top-level of the plugin repository: - ``./devstack/files/debs/$plugin_name`` - Packages to install when running on Ubuntu, Debian or Linux Mint. - ``./devstack/files/rpms/$plugin_name`` - Packages to install when running on Red Hat, Fedora, CentOS or XenServer. - ``./devstack/files/rpms-suse/$plugin_name`` - Packages to install when running on SUSE Linux or openSUSE.