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39 lines
2.5 KiB
39 lines
2.5 KiB
<h1>Signalling failures</h1>
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<p>Append <code>/fail</code> to a ping URL and use it to actively signal a failure.
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Requesting the <code>/fail</code> URL will immediately mark the check as "down".
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You can use this feature to minimize the delay from your monitored service failing
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to you getting a notification.</p>
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<h2>Shell Scripts</h2>
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<p>The below shell script sends either a "success" or "failure" ping depending on
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command's (certbot in this example) exit code:</p>
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<div class="highlight"><pre><span></span><code><span class="ch">#!/bin/sh</span>
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<span class="nv">url</span><span class="o">=</span>PING_URL
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/usr/bin/certbot renew
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<span class="k">if</span> <span class="o">[</span> <span class="nv">$?</span> -ne <span class="m">0</span> <span class="o">]</span><span class="p">;</span> <span class="k">then</span> <span class="nv">url</span><span class="o">=</span><span class="nv">$url</span>/fail<span class="p">;</span> <span class="k">fi</span>
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curl --retry <span class="m">3</span> <span class="nv">$url</span>
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</code></pre></div>
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<h2>Python</h2>
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<p>Below is a skeleton code example in Python which signals a failure when the
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work function returns an unexpected value or throws an exception:</p>
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<div class="highlight"><pre><span></span><code><span class="kn">import</span> <span class="nn">requests</span>
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<span class="n">URL</span> <span class="o">=</span> <span class="s2">"PING_URL"</span>
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<span class="k">def</span> <span class="nf">do_work</span><span class="p">():</span>
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<span class="c1"># Do your number crunching, backup dumping, newsletter sending work here.</span>
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<span class="c1"># Return a truthy value on success.</span>
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<span class="c1"># Return a falsy value or throw an exception on failure.</span>
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<span class="k">return</span> <span class="kc">True</span>
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<span class="n">success</span> <span class="o">=</span> <span class="kc">False</span>
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<span class="k">try</span><span class="p">:</span>
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<span class="n">success</span> <span class="o">=</span> <span class="n">do_work</span><span class="p">()</span>
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<span class="k">finally</span><span class="p">:</span>
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<span class="c1"># On success, requests PING_URL</span>
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<span class="c1"># On failure, requests PING_URL/fail</span>
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<span class="n">requests</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">URL</span> <span class="k">if</span> <span class="n">success</span> <span class="k">else</span> <span class="n">URL</span> <span class="o">+</span> <span class="s2">"/fail"</span><span class="p">)</span>
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</code></pre></div>
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