113 lines
3.9 KiB
ReStructuredText
113 lines
3.9 KiB
ReStructuredText
=======
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Plugins
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=======
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DevStack has a couple of plugin mechanisms to allow easily adding
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support for additional projects and features.
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Extras.d Hooks
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~~~~~~~~~~~~~~
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These relatively new hooks are an extension of the existing calls from
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``stack.sh`` at the end of its run, plus ``unstack.sh`` and
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``clean.sh``. A number of the higher-layer projects are implemented in
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DevStack using this mechanism.
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The script in ``extras.d`` is expected to be mostly a dispatcher to
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functions in a ``lib/*`` script. The scripts are named with a
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zero-padded two digits sequence number prefix to control the order that
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the scripts are called, and with a suffix of ``.sh``. DevSack reserves
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for itself the sequence numbers 00 through 09 and 90 through 99.
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Below is a template that shows handlers for the possible command-line
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arguments:
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::
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# template.sh - DevStack extras.d dispatch script template
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# check for service enabled
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if is_service_enabled template; then
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if [[ "$1" == "source" ]]; then
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# Initial source of lib script
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source $TOP_DIR/lib/template
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fi
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if [[ "$1" == "stack" && "$2" == "pre-install" ]]; then
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# Set up system services
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echo_summary "Configuring system services Template"
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install_package cowsay
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elif [[ "$1" == "stack" && "$2" == "install" ]]; then
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# Perform installation of service source
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echo_summary "Installing Template"
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install_template
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elif [[ "$1" == "stack" && "$2" == "post-config" ]]; then
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# Configure after the other layer 1 and 2 services have been configured
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echo_summary "Configuring Template"
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configure_template
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elif [[ "$1" == "stack" && "$2" == "extra" ]]; then
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# Initialize and start the template service
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echo_summary "Initializing Template"
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##init_template
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fi
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if [[ "$1" == "unstack" ]]; then
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# Shut down template services
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# no-op
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:
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fi
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if [[ "$1" == "clean" ]]; then
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# Remove state and transient data
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# Remember clean.sh first calls unstack.sh
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# no-op
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:
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fi
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fi
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The arguments are:
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- **source** - Called by each script that utilizes ``extras.d`` hooks;
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this replaces directly sourcing the ``lib/*`` script.
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- **stack** - Called by ``stack.sh`` three times for different phases
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of its run:
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- **pre-install** - Called after system (OS) setup is complete and
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before project source is installed.
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- **install** - Called after the layer 1 and 2 projects source and
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their dependencies have been installed.
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- **post-config** - Called after the layer 1 and 2 services have
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been configured. All configuration files for enabled services
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should exist at this point.
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- **extra** - Called near the end after layer 1 and 2 services have
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been started. This is the existing hook and has not otherwise
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changed.
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- **unstack** - Called by ``unstack.sh`` before other services are shut
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down.
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- **clean** - Called by ``clean.sh`` before other services are cleaned,
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but after ``unstack.sh`` has been called.
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Hypervisor
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~~~~~~~~~~
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Hypervisor plugins are fairly new and condense most hypervisor
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configuration into one place.
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The initial plugin implemented was for Docker support and is a useful
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template for the required support. Plugins are placed in
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``lib/nova_plugins`` and named ``hypervisor-<name>`` where ``<name>`` is
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the value of ``VIRT_DRIVER``. Plugins must define the following
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functions:
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- ``install_nova_hypervisor`` - install any external requirements
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- ``configure_nova_hypervisor`` - make configuration changes, including
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those to other services
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- ``start_nova_hypervisor`` - start any external services
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- ``stop_nova_hypervisor`` - stop any external services
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- ``cleanup_nova_hypervisor`` - remove transient data and cache
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