title: Prometheus + blackbox component -> How to monitoring HTTP content without seperate checks
body: <p>I have prometheus working with blackbox component, and wish to pass parameters to the blackbox component - Apart from module and target which already work quite well.</p>
  
  <p>I am looking for a way to pass in keys like 'fail_if_not_matches_regexp' and other parameters which can be set in the blackbox component, and for the pass in values to override the existing ones. Do I need to be writing relabel_configs for blackbox component?</p>
  
  <p>Currently I have prometheus passing in key/value pairs to the URL, however I'm not sure what the key should be in the URL.</p>
  
  <p><a href="http://localhost:9115/probe?module=http_2xx&amp;modules_fail_if_not_matches_regexp=1234&amp;target=https%3A%2F%2Fwww.xyz.com" rel="nofollow noreferrer">http://localhost:9115/probe?module=http_2xx&amp;modules_fail_if_not_matches_regexp=1234&amp;target=https%3A%2F%2Fwww.xyz.com</a></p>
  
  <p>This leads to the question of which blackbox component variables can I set using the URL key/value pairs?</p>
  
  <p>Also, I could create seperate blackbox configurations which contain the static text and options to check for each target, however I would rather something dynamic which using the discovery JSON file method (which current works for setting target params).</p>
  
  <pre><code>    {
        "targets": [ "https://yyy" ],
        "labels": {
          "fail_if_not_matches_regexp": "web services under your control",
        }
      },
  </code></pre>