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46 <section id="faq" class="span12">
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48 <div class='row pull-left'>
49 <h2>Plugins <small>Add stuff</small></h2>
50 <p>DevStack has a couple of plugin mechanisms to allow easily adding support for additional projects and features.</p>
51
52 <h3>Extras.d Hooks</h3>
53 <p>These relatively new hooks are an extension of the existing calls from <code>stack.sh</code> at the end of its run, plus <code>unstack.sh</code> and <code>clean.sh</code>. A number of the higher-layer projects are implemented in DevStack using this mechanism.</p>
54
55 <p>The script in <code>extras.d</code> is expected to be mostly a dispatcher to functions in a <code>lib/*</code> 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 <code>.sh</code>. DevSack reserves for itself the sequence numbers 00 through 09 and 90 through 99.</p>
56
57 <p>Below is a template that shows handlers for the possible command-line arguments:</p>
58
59<pre>
60# template.sh - DevStack extras.d dispatch script template
61
62# check for service enabled
63if is_service_enabled template; then
64
65 if [[ "$1" == "source" ]]; then
66 # Initial source of lib script
67 source $TOP_DIR/lib/template
68 fi
69
70 if [[ "$1" == "stack" && "$2" == "install" ]]; then
71 # Perform installation of service source
72 echo_summary "Installing Template"
73 install_template
74
75 elif [[ "$1" == "stack" && "$2" == "post-config" ]]; then
76 # Configure after the other layer 1 and 2 services have been configured
77 echo_summary "Configuring Template"
78 configure_template
79
80 elif [[ "$1" == "stack" && "$2" == "extra" ]]; then
81 # Initialize and start the template service
82 echo_summary "Initializing Template"
83 ##init_template
84 fi
85
86 if [[ "$1" == "unstack" ]]; then
87 # Shut down template services
88 # no-op
89 :
90 fi
91
92 if [[ "$1" == "clean" ]]; then
93 # Remove state and transient data
94 # Remember clean.sh first calls unstack.sh
95 # no-op
96 :
97 fi
98fi
99</pre>
100
101 <p>The arguments are:
102 <ul>
103 <li><strong>source</strong> - Called by each script that utilizes <code>extras.d</code> hooks; this replaces directly sourcing the <code>lib/*</code> script.</li>
104 <li><strong>stack</strong> - Called by <code>stack.sh</code> three times for different phases of its run:
105 <ul>
106 <li><strong>install</strong> - Called after the layer 1 and 2 projects source and their dependencies have been installed.</li>
107 <li><strong>post-config</strong> - Called after the layer 1 and 2 services have been configured. All configuration files for enabled services should exist at this point.</li>
108 <li><strong>extra</strong> - Called near the end after layer 1 and 2 services have been started. This is the existing hook and has not otherwise changed.</li>
109 </ul></li>
110 <li><strong>unstack</strong> - Called by <code>unstack.sh</code> before other services are shut down.</li>
111 <li><strong>clean</strong> - Called by <code>clean.sh</code> before other services are cleaned, but after <code>unstack.sh</code> has been called.
112 </ul></p>
113
114
115 <h3>Hypervisor</h3>
116 <p>Hypervisor plugins are fairly new and condense most hypervisor configuration into one place.</p>
117
118 <p>The initial plugin implemented was for Docker support and is a useful template for the required support. Plugins are placed in <code>lib/nova_plugins</code> and named <code>hypervisor-&lt;name&gt;</code> where <code>&lt;name&gt;</code> is the value of <code>VIRT_DRIVER</code>. Plugins must define the following functions:</p>
119 <ul>
120 <li><code>install_nova_hypervisor</code> - install any external requirements</li>
121 <li><code>configure_nova_hypervisor</code> - make configuration changes, including those to other services</li>
122 <li><code>start_nova_hypervisor</code> - start any external services</li>
123 <li><code>stop_nova_hypervisor</code> - stop any external services</li>
124 <li><code>cleanup_nova_hypervisor</code> - remove transient data and cache</li>
125 </ul>
126 </div>
127
128 </section>
129
130 <footer>
131 <p>&copy; Openstack Foundation 2011-2013 &mdash; An <a href="https://wiki.openstack.org/wiki/Programs">OpenStack program</a> created by <a href="http://www.rackspace.com/cloud/private_edition/">Rackspace Cloud Builders</a></p>
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