You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
31 lines
1.8 KiB
31 lines
1.8 KiB
<h1>Pinging Reliability Tips</h1>
|
|
<p>Sending monitoring signals over the public internet is inherently unreliable.
|
|
HTTP requests can sometimes take excessively long or fail completely
|
|
for a variety of reasons. Here are some general tips to make your monitoring
|
|
code more robust.</p>
|
|
<h2>Specify HTTP Request Timeout</h2>
|
|
<p>Put a time limit on how long each ping is allowed to take. This is especially
|
|
important when sending a "start" signal at the start of a job: you don't want
|
|
a stuck ping to prevent the actual job from running. Another case is a continuously
|
|
running worker process that pings SITE_NAME after each completed item. A stuck
|
|
request could block the whole process. An explicit per-request time limit mitigates
|
|
this problem.</p>
|
|
<p>Specifying the timeout depends on the tool you use. curl, for example, has the
|
|
<code>--max-time</code> (shorthand: <code>-m</code>) parameter:</p>
|
|
<div class="highlight"><pre><span></span><code><span class="c1"># Send an HTTP request, 10 second timeout:</span>
|
|
curl -m <span class="m">10</span> PING_URL
|
|
</code></pre></div>
|
|
|
|
<h2>Use Retries</h2>
|
|
<p>To minimize the amount of false alerts you get from SITE_NAME, instruct your HTTP
|
|
client to retry failed requests several times.</p>
|
|
<p>Specifying the retry policy depends on the tool you use. curl, for example, has the
|
|
<code>--retry</code> parameter:</p>
|
|
<div class="highlight"><pre><span></span><code><span class="c1"># Retry up to 5 times, uses an increasing delay between each retry (1s, 2s, 4s, 8s, ...)</span>
|
|
curl --retry <span class="m">5</span> PING_URL
|
|
</code></pre></div>
|
|
|
|
<h2>Handle Exceptions</h2>
|
|
<p>Make sure you know how your HTTP client handles failed requests. For example,
|
|
if you use an HTTP library that raises exceptions, decide if you want to
|
|
catch the exceptions or let them bubble up.</p>
|