In our static infrastructure test environment, we can validate the configuration of blackbox_exporter by connecting to the target01 instance as shown here:

cd ./chapter06/

vagrant ssh target01

Then checking the configuration of the provided systemd unit file as shown in the following command:

vagrant@target01:~$ systemctl cat blackbox-exporter

We can see all the required arguments for the blackbox_exporter service in the following snippet from the unit file, including the path to the configuration file:

...
ExecStart=/usr/bin/blackbox_exporter --config.file=/etc/blackbox_exporter/blackbox.yml
...

The configuration we tailored for our example can be found in the following snippet:

modules:
  http_2xx:
    prober: http
    http:
      preferred_ip_protocol: ip4

  icmp:
    prober: icmp
    icmp:
      preferred_ip_protocol: ip4

On the Prometheus instance, we added the following jobs:

- job_name: 'blackbox-http'
    metrics_path: /probe
    params:
      module: [http_2xx]
    static_configs:
      - targets: [ 'http://example.com', 'https://example.com:443' ]
...
  - job_name: 'blackbox-icmp'
    metrics_path: /probe
    params:
      module: [icmp]
    static_configs:
      - targets:
         - prometheus
...

Using the Prometheus web interface, available at http://192.168.42.10:9090/targets, we can validate whether the scrapes are successful (independently of the return status of the probes):

As mentioned before, the /targets page doesn't tell you whether a probe was successful or not. This needs to be validated in the expression browser by querying the probe_success metric:

Some interesting metrics that can be collected from blackbox_exporter (both about the exporter itself and from probes) are:

• blackbox_exporter_config_last_reload_successful, which exposes if the exporter's configuration file was reloaded successfully after a SIGHUP
• probe_http_status_code, which allows you to understand what HTTP status code is being returned when using the HTTP prober module
• probe_ssl_earliest_cert_expiry, which returns the timestamp for when the certificate chain from a SSL probe becomes invalid due to one of the certificates in the chain expiring