title: how to solve the promethesus blackbox_exporter 401 error
body: <p>I want to use "fail_if_body_not_matches_regexp" in blackbox_exporter to detect whether a string is returned in an HTTP interface (this interface is a url of type GET), but the result of blackbox_exporter page is always 401. by the way, I can normally access this interface through the browser and get the results</p>
  
  <p>I wanted to detect rabbitMQ for split brain, but rabbitmq_exporter could not detect split brain.So I use HTTP probe in blackbox_exporter to do regexp match the results of the interface.But when I configured everything done. I visit 
   the url "<a href="http://10.201.5.197:9115/probe?module=http_2rabbitmq_brainSplit&amp;target=10.201.7.209%3A15672%2Fapi%2Fnodes" rel="nofollow noreferrer">http://10.201.5.197:9115/probe?module=http_2rabbitmq_brainSplit&amp;target=10.201.7.209%3A15672%2Fapi%2Fnodes</a>".And blackbox always display 401, as shown below</p>
  
  <pre><code># HELP probe_dns_lookup_time_seconds Returns the time taken for probe dns lookup in seconds
  # TYPE probe_dns_lookup_time_seconds gauge
  probe_dns_lookup_time_seconds 3.6954e-05
  # HELP probe_duration_seconds Returns how long the probe took to complete in seconds
  # TYPE probe_duration_seconds gauge
  probe_duration_seconds 0.002106961
  # HELP probe_failed_due_to_regex Indicates if probe failed due to regex
  # TYPE probe_failed_due_to_regex gauge
  probe_failed_due_to_regex 1
  # HELP probe_http_content_length Length of http content response
  # TYPE probe_http_content_length gauge
  probe_http_content_length 54
  # HELP probe_http_duration_seconds Duration of http request by phase, summed over all redirects
  # TYPE probe_http_duration_seconds gauge
  probe_http_duration_seconds{phase="connect"} 0.000388833
  probe_http_duration_seconds{phase="processing"} 0.001160027
  probe_http_duration_seconds{phase="resolve"} 3.6954e-05
  probe_http_duration_seconds{phase="tls"} 0
  probe_http_duration_seconds{phase="transfer"} 0.000159596
  # HELP probe_http_redirects The number of redirects
  # TYPE probe_http_redirects gauge
  probe_http_redirects 0
  # HELP probe_http_ssl Indicates if SSL was used for the final redirect
  # TYPE probe_http_ssl gauge
  probe_http_ssl 0
  # HELP probe_http_status_code Response HTTP status code
  # TYPE probe_http_status_code gauge
  probe_http_status_code 401
  # HELP probe_http_version Returns the version of HTTP of the probe response
  # TYPE probe_http_version gauge
  probe_http_version 1.1
  # HELP probe_ip_protocol Specifies whether probe ip protocol is IP4 or IP6
  # TYPE probe_ip_protocol gauge
  probe_ip_protocol 4
  # HELP probe_success Displays whether or not the probe was a success
  # TYPE probe_success gauge
  probe_success 0
  </code></pre>
  
  <p>My prometheus config.yaml:</p>
  
  <pre><code>  - job_name: 'rabbitma_brainSplit'
      metrics_path: /probe
      basic_auth:
        username: admin
        password: GSS1duS1Zdda
      params:
        module: [http_2rabbitmq_brainSplit]  
      static_configs:
        - targets:
          - 10.201.7.209:15672/api/nodes   
      relabel_configs:
        - source_labels: [__address__]
          target_label: __param_target
        - source_labels: [__param_target]
          target_label: instance
        - target_label: __address__
          replacement: 10.201.5.197:9115
  </code></pre>
  
  <p>My black_exporter config.yml:</p>
  
  <pre><code>modules:
    http_2rabbitmq_brainSplit:
      prober: http
      timeout: 10s
      http:
        valid_http_versions: ["HTTP/1.1", "HTTP/2"]
        valid_status_codes: []  
        method: GET
        headers:
          Accept-Language: zh-CN,zh;q=0.9
        no_follow_redirects: false
        fail_if_ssl: false
        fail_if_not_ssl: false
        fail_if_body_not_matches_regexp:
        - '\"partitions\":\[\s+\]'
  </code></pre>
  
  <p>I expected the regexp match result of the fail_if_body_not_matches_regexp.
  Did I configure something wrong?</p>