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<div class="section" id="usage">
<h1>Usage<a class="headerlink" href="#usage" title="Permalink to this headline">¶</a></h1>
<p>To use oslo.service in a project:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">oslo_service</span>
</pre></div>
</div>
<div class="section" id="migrating-to-oslo-service">
<h2>Migrating to oslo.service<a class="headerlink" href="#migrating-to-oslo-service" title="Permalink to this headline">¶</a></h2>
<p>The <code class="docutils literal"><span class="pre">oslo.service</span></code> library no longer assumes a global configuration object is
available. Instead the following functions and classes have been
changed to expect the consuming application to pass in an <code class="docutils literal"><span class="pre">oslo.config</span></code>
configuration object:</p>
<ul class="simple">
<li><code class="xref py py-func docutils literal"><span class="pre">initialize_if_enabled()</span></code></li>
<li><a class="reference internal" href="api/periodic_task.html#oslo_service.periodic_task.PeriodicTasks" title="oslo_service.periodic_task.PeriodicTasks"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.periodic_task.PeriodicTasks</span></code></a></li>
<li><a class="reference internal" href="api/service.html#oslo_service.service.launch" title="oslo_service.service.launch"><code class="xref py py-func docutils literal"><span class="pre">launch()</span></code></a></li>
<li><a class="reference internal" href="api/service.html#oslo_service.service.ProcessLauncher" title="oslo_service.service.ProcessLauncher"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.service.ProcessLauncher</span></code></a></li>
<li><a class="reference internal" href="api/service.html#oslo_service.service.ServiceLauncher" title="oslo_service.service.ServiceLauncher"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.service.ServiceLauncher</span></code></a></li>
<li><a class="reference internal" href="api/sslutils.html#oslo_service.sslutils.is_enabled" title="oslo_service.sslutils.is_enabled"><code class="xref py py-func docutils literal"><span class="pre">is_enabled()</span></code></a></li>
<li><a class="reference internal" href="api/sslutils.html#oslo_service.sslutils.wrap" title="oslo_service.sslutils.wrap"><code class="xref py py-func docutils literal"><span class="pre">wrap()</span></code></a></li>
</ul>
<div class="section" id="when-using-service-from-oslo-incubator">
<h3>When using service from oslo-incubator<a class="headerlink" href="#when-using-service-from-oslo-incubator" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">foo.openstack.common</span> <span class="kn">import</span> <span class="n">service</span>
<span class="n">launcher</span> <span class="o">=</span> <span class="n">service</span><span class="o">.</span><span class="n">launch</span><span class="p">(</span><span class="n">service</span><span class="p">,</span> <span class="n">workers</span><span class="o">=</span><span class="mi">2</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="when-using-oslo-service">
<h3>When using oslo.service<a class="headerlink" href="#when-using-oslo-service" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">oslo_config</span> <span class="kn">import</span> <span class="n">cfg</span>
<span class="kn">from</span> <span class="nn">oslo_service</span> <span class="kn">import</span> <span class="n">service</span>
<span class="n">CONF</span> <span class="o">=</span> <span class="n">cfg</span><span class="o">.</span><span class="n">CONF</span>
<span class="n">launcher</span> <span class="o">=</span> <span class="n">service</span><span class="o">.</span><span class="n">launch</span><span class="p">(</span><span class="n">CONF</span><span class="p">,</span> <span class="n">service</span><span class="p">,</span> <span class="n">workers</span><span class="o">=</span><span class="mi">2</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="using-oslo-service-with-oslo-config-generator">
<h3>Using oslo.service with oslo-config-generator<a class="headerlink" href="#using-oslo-service-with-oslo-config-generator" title="Permalink to this headline">¶</a></h3>
<p>The <code class="docutils literal"><span class="pre">oslo.service</span></code> provides several entry points to generate a configuration
files.</p>
<ul>
<li><dl class="first docutils">
<dt><a class="reference internal" href="api/service.html#oslo_service.service.list_opts" title="oslo_service.service.list_opts"><code class="xref py py-func docutils literal"><span class="pre">oslo.service.service</span></code></a></dt>
<dd><p class="first last">The options from the service and eventlet_backdoor modules for
the [DEFAULT] section.</p>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><a class="reference internal" href="api/periodic_task.html#oslo_service.periodic_task.list_opts" title="oslo_service.periodic_task.list_opts"><code class="xref py py-func docutils literal"><span class="pre">oslo.service.periodic_task</span></code></a></dt>
<dd><p class="first last">The options from the periodic_task module for the [DEFAULT] section.</p>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><a class="reference internal" href="api/sslutils.html#oslo_service.sslutils.list_opts" title="oslo_service.sslutils.list_opts"><code class="xref py py-func docutils literal"><span class="pre">oslo.service.sslutils</span></code></a></dt>
<dd><p class="first last">The options from the sslutils module for the [ssl] section.</p>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><code class="xref py py-func docutils literal"><span class="pre">oslo.service.wsgi</span></code></dt>
<dd><p class="first last">The options from the wsgi module for the [DEFAULT] section.</p>
</dd>
</dl>
</li>
</ul>
<p><strong>ATTENTION:</strong> The library doesn’t provide an oslo.service entry point.</p>
<div class="highlight-bash"><div class="highlight"><pre>$ oslo-config-generator --namespace oslo.service.service <span class="se">\</span>
--namespace oslo.service.periodic_task <span class="se">\</span>
--namespace oslo.service.sslutils
</pre></div>
</div>
</div>
</div>
<div class="section" id="launching-and-controlling-services">
<h2>Launching and controlling services<a class="headerlink" href="#launching-and-controlling-services" title="Permalink to this headline">¶</a></h2>
<p>oslo_service.service module provides tools for launching OpenStack
services and controlling their lifecycles.</p>
<p>A service is an instance of any class that
subclasses <a class="reference internal" href="api/service.html#oslo_service.service.ServiceBase" title="oslo_service.service.ServiceBase"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.service.ServiceBase</span></code></a>.
<a class="reference internal" href="api/service.html#oslo_service.service.ServiceBase" title="oslo_service.service.ServiceBase"><code class="xref py py-class docutils literal"><span class="pre">ServiceBase</span></code></a> is an
abstract class that defines an interface every
service should implement. <a class="reference internal" href="api/service.html#oslo_service.service.Service" title="oslo_service.service.Service"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.service.Service</span></code></a> can
serve as a base for constructing new services.</p>
<div class="section" id="launchers">
<h3>Launchers<a class="headerlink" href="#launchers" title="Permalink to this headline">¶</a></h3>
<p>oslo_service.service module provides two launchers for running services:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="api/service.html#oslo_service.service.ServiceLauncher" title="oslo_service.service.ServiceLauncher"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.service.ServiceLauncher</span></code></a> - used for
running one or more service in a parent process.</li>
<li><a class="reference internal" href="api/service.html#oslo_service.service.ProcessLauncher" title="oslo_service.service.ProcessLauncher"><code class="xref py py-class docutils literal"><span class="pre">oslo_service.service.ProcessLauncher</span></code></a> - forks a given
number of workers in which service(s) are then started.</li>
</ul>
</div></blockquote>
<p>It is possible to initialize whatever launcher is needed and then
launch a service using it.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">oslo_config</span> <span class="kn">import</span> <span class="n">cfg</span>
<span class="kn">from</span> <span class="nn">oslo_service</span> <span class="kn">import</span> <span class="n">service</span>
<span class="n">CONF</span> <span class="o">=</span> <span class="n">cfg</span><span class="o">.</span><span class="n">CONF</span>
<span class="n">service_launcher</span> <span class="o">=</span> <span class="n">service</span><span class="o">.</span><span class="n">ServiceLauncher</span><span class="p">(</span><span class="n">CONF</span><span class="p">)</span>
<span class="n">service_launcher</span><span class="o">.</span><span class="n">launch_service</span><span class="p">(</span><span class="n">service</span><span class="o">.</span><span class="n">Service</span><span class="p">())</span>
<span class="n">process_launcher</span> <span class="o">=</span> <span class="n">service</span><span class="o">.</span><span class="n">ProcessLauncher</span><span class="p">(</span><span class="n">CONF</span><span class="p">,</span> <span class="n">wait_interval</span><span class="o">=</span><span class="mf">1.0</span><span class="p">)</span>
<span class="n">process_launcher</span><span class="o">.</span><span class="n">launch_service</span><span class="p">(</span><span class="n">service</span><span class="o">.</span><span class="n">Service</span><span class="p">(),</span> <span class="n">workers</span><span class="o">=</span><span class="mi">2</span><span class="p">)</span>
</pre></div>
</div>
<p>Or one can simply call <a class="reference internal" href="api/service.html#oslo_service.service.launch" title="oslo_service.service.launch"><code class="xref py py-func docutils literal"><span class="pre">oslo_service.service.launch()</span></code></a> which will
automatically pick an appropriate launcher based on a number of workers that
are passed to it (ServiceLauncher in case workers=1 or None and
ProcessLauncher in other case).</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">oslo_config</span> <span class="kn">import</span> <span class="n">cfg</span>
<span class="kn">from</span> <span class="nn">oslo_service</span> <span class="kn">import</span> <span class="n">service</span>
<span class="n">CONF</span> <span class="o">=</span> <span class="n">cfg</span><span class="o">.</span><span class="n">CONF</span>
<span class="n">launcher</span> <span class="o">=</span> <span class="n">service</span><span class="o">.</span><span class="n">launch</span><span class="p">(</span><span class="n">CONF</span><span class="p">,</span> <span class="n">service</span><span class="o">.</span><span class="n">Service</span><span class="p">(),</span> <span class="n">workers</span><span class="o">=</span><span class="mi">3</span><span class="p">)</span>
</pre></div>
</div>
<p><em>NOTE:</em> Please be informed that it is highly recommended to use no
more than one instance of ServiceLauncher and ProcessLauncher classes
per process.</p>
</div>
<div class="section" id="signal-handling">
<h3>Signal handling<a class="headerlink" href="#signal-handling" title="Permalink to this headline">¶</a></h3>
<p>oslo_service.service provides handlers for such signals as SIGTERM, SIGINT
and SIGHUP.</p>
<p>SIGTERM is used for graceful termination of services. This can allow a
server to wait for all clients to close connections while rejecting new
incoming requests. Config option graceful_shutdown_timeout specifies how
many seconds after receiving a SIGTERM signal, a server should continue
to run, handling the existing connections. Setting graceful_shutdown_timeout
to zero means that the server will wait indefinitely until all remaining
requests have been fully served.</p>
<p>To force instantaneous termination SIGINT signal must be sent.</p>
<p>On receiving SIGHUP configuration files are reloaded and a service
is being reset and started again. Then all child workers are gracefully
stopped using SIGTERM and workers with new configuration are
spawned. Thus, SIGHUP can be used for changing config options on the go.</p>
<p><em>NOTE:</em> SIGHUP is not supported on Windows.
<em>NOTE:</em> Config option graceful_shutdown_timeout is not supported on Windows.</p>
<p>Below is the example of a service with a reset method that allows reloading
logging options by sending a SIGHUP.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">oslo_config</span> <span class="kn">import</span> <span class="n">cfg</span>
<span class="kn">from</span> <span class="nn">oslo_log</span> <span class="kn">import</span> <span class="n">log</span> <span class="k">as</span> <span class="n">logging</span>
<span class="kn">from</span> <span class="nn">oslo_service</span> <span class="kn">import</span> <span class="n">service</span>
<span class="n">CONF</span> <span class="o">=</span> <span class="n">cfg</span><span class="o">.</span><span class="n">CONF</span>
<span class="n">LOG</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">FooService</span><span class="p">(</span><span class="n">service</span><span class="o">.</span><span class="n">ServiceBase</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">start</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">pass</span>
<span class="k">def</span> <span class="nf">wait</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">pass</span>
<span class="k">def</span> <span class="nf">stop</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">pass</span>
<span class="k">def</span> <span class="nf">reset</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">logging</span><span class="o">.</span><span class="n">setup</span><span class="p">(</span><span class="n">cfg</span><span class="o">.</span><span class="n">CONF</span><span class="p">,</span> <span class="s1">'foo'</span><span class="p">)</span>
</pre></div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Usage</a><ul>
<li><a class="reference internal" href="#migrating-to-oslo-service">Migrating to oslo.service</a><ul>
<li><a class="reference internal" href="#when-using-service-from-oslo-incubator">When using service from oslo-incubator</a></li>
<li><a class="reference internal" href="#when-using-oslo-service">When using oslo.service</a></li>
<li><a class="reference internal" href="#using-oslo-service-with-oslo-config-generator">Using oslo.service with oslo-config-generator</a></li>
</ul>
</li>
<li><a class="reference internal" href="#launching-and-controlling-services">Launching and controlling services</a><ul>
<li><a class="reference internal" href="#launchers">Launchers</a></li>
<li><a class="reference internal" href="#signal-handling">Signal handling</a></li>
</ul>
</li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="installation.html"
title="previous chapter">Installation</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="opts.html"
title="next chapter">Configuration Options</a></p>
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