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www.nico.schottelius.org/software/cdist/man/4.4.3/cdist-messaging.html
Darko Poljak bec13a88c0 cdist manpages update: 4.4.3
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<li class="toctree-l1 current"><a class="current reference internal" href="#">15. Messaging</a><ul>
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<div class="section" id="messaging">
<h1>15. Messaging<a class="headerlink" href="#messaging" title="Permalink to this headline"></a></h1>
<div class="section" id="description">
<h2>15.1. Description<a class="headerlink" href="#description" title="Permalink to this headline"></a></h2>
<p>cdist has a simple but powerful way of allowing communication between
the initial manifest and types as well as types and types.</p>
<p>Whenever execution is passed from cdist to one of the
scripts described below, cdist generate 2 new temporary files
and exports the environment variables <strong>__messages_in</strong> and
<strong>__messages_out</strong> to point to them.</p>
<p>Before handing over the control, the content of the global message
file is copied into the file referenced by <strong>$__messages_in</strong>.</p>
<p>After cdist gained control back, the content of the file referenced
by <strong>$__messages_out</strong> is appended to the global message file.</p>
<p>This way overwriting any of the two files by accident does not
interfere with other types.</p>
<p>The order of execution is not defined unless you create dependencies
between the different objects (see <a class="reference external" href="cdist-manifest.html">cdist manifest</a>) and thus you
can only react reliably on messages by objects that you depend on.</p>
</div>
<div class="section" id="availability">
<h2>15.2. Availability<a class="headerlink" href="#availability" title="Permalink to this headline"></a></h2>
<p>Messaging is possible between all <strong>local</strong> scripts:</p>
<ul class="simple">
<li>initial manifest</li>
<li>type/manifest</li>
<li>type/gencode-local</li>
<li>type/gencode-remote</li>
</ul>
</div>
<div class="section" id="examples">
<h2>15.3. Examples<a class="headerlink" href="#examples" title="Permalink to this headline"></a></h2>
<p>When you want to emit a message use:</p>
<div class="highlight-sh"><div class="highlight"><pre><span></span><span class="nb">echo</span> <span class="s2">&quot;something&quot;</span> &gt;&gt; <span class="s2">&quot;</span><span class="nv">$__messages_out</span><span class="s2">&quot;</span>
</pre></div>
</div>
<p>When you want to react on a message use:</p>
<div class="highlight-sh"><div class="highlight"><pre><span></span><span class="k">if</span> grep -q <span class="s2">&quot;^__your_type/object/id:something&quot;</span> <span class="s2">&quot;</span><span class="nv">$__messages_in</span><span class="s2">&quot;</span><span class="p">;</span> <span class="k">then</span>
<span class="nb">echo</span> <span class="s2">&quot;I do something else&quot;</span>
<span class="k">fi</span>
</pre></div>
</div>
<p>Some real life examples:</p>
<div class="highlight-sh"><div class="highlight"><pre><span></span><span class="c1"># Reacting on changes from block for keepalive</span>
<span class="k">if</span> grep -q <span class="s2">&quot;^__block/keepalive-vrrp&quot;</span> <span class="s2">&quot;</span><span class="nv">$__messages_in</span><span class="s2">&quot;</span><span class="p">;</span> <span class="k">then</span>
<span class="nb">echo</span> /etc/init.d/keepalived restart
<span class="k">fi</span>
<span class="c1"># Reacting on changes of configuration files</span>
<span class="k">if</span> grep -q <span class="s2">&quot;^__file/etc/one&quot;</span> <span class="nv">$__messages_in</span><span class="p">;</span> <span class="k">then</span>
<span class="nb">echo</span> <span class="s1">&#39;for init in /etc/init.d/opennebula*; do $init restart; done&#39;</span>
<span class="k">fi</span>
</pre></div>
</div>
<p>Restart sshd on changes</p>
<div class="highlight-sh"><div class="highlight"><pre><span></span><span class="nv">os</span><span class="o">=</span><span class="s2">&quot;</span><span class="k">$(</span>cat <span class="s2">&quot;</span><span class="nv">$__global</span><span class="s2">/explorer/os&quot;</span><span class="k">)</span><span class="s2">&quot;</span>
<span class="k">case</span> <span class="s2">&quot;</span><span class="nv">$os</span><span class="s2">&quot;</span> in
centos<span class="p">|</span>redhat<span class="p">|</span>suse<span class="o">)</span>
<span class="nv">restart</span><span class="o">=</span><span class="s2">&quot;/etc/init.d/sshd restart&quot;</span>
<span class="p">;;</span>
debian<span class="p">|</span>ubuntu<span class="o">)</span>
<span class="nv">restart</span><span class="o">=</span><span class="s2">&quot;/etc/init.d/ssh restart&quot;</span>
<span class="p">;;</span>
*<span class="o">)</span>
cat <span class="s">&lt;&lt; eof &gt;&amp;2</span>
<span class="s">Unsupported os $os.</span>
<span class="s">If you would like to have this type running on $os,</span>
<span class="s">you can either develop the changes and send a pull</span>
<span class="s">request or ask for a quote at www.ungleich.ch</span>
<span class="s">eof</span>
<span class="nb">exit</span> <span class="m">1</span>
<span class="p">;;</span>
<span class="k">esac</span>
<span class="k">if</span> grep -q <span class="s2">&quot;^__key_value/PermitRootLogin&quot;</span> <span class="s2">&quot;</span><span class="nv">$__messages_in</span><span class="s2">&quot;</span><span class="p">;</span> <span class="k">then</span>
<span class="nb">echo</span> <span class="nv">$restart</span>
<span class="k">fi</span>
</pre></div>
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