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44 lines
2.7 KiB
44 lines
2.7 KiB
<h1>Signaling failures</h1>
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<p>You can actively signal a failure to SITE_NAME by slightly changing the
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ping URL: append either <code>/fail</code> or <code>/{exit-status}</code> to your normal ping URL.
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The exit status should be a 0-255 integer. SITE_NAME will interpret
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exit status 0 as success and all non-zero values as failures.</p>
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<p>Examples:</p>
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<div class="highlight"><pre><span></span><code><span class="c1"># Reports failure by appending the /fail suffix:</span>
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curl --retry <span class="m">3</span> PING_URL/fail
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<span class="c1"># Reports failure by appending a non-zero exit status:</span>
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curl --retry <span class="m">3</span> PING_URL/1
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</code></pre></div>
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<p>By actively signaling failures to SITE_NAME, you can minimize the delay from your
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monitored service encountering a problem to you getting notified about it.</p>
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<h2>Shell Scripts</h2>
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<p>The below shell script appends <code>$?</code> (a special variable which contains the
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exit status of the last executed command) to the ping URL:</p>
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<div class="highlight"><pre><span></span><code><span class="ch">#!/bin/sh</span>
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/usr/bin/certbot renew
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curl --retry <span class="m">3</span> PING_URL/<span class="nv">$?</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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