title: Prometheus not reading blackbox targets from file_sd_configs
body: <p>I'm configuring blackbox for monitoring my websites. Prometheus static config targets are working but are also little bit messy. I would to put all my targets into file but its not working at all.</p>
  
  <p>docker-compose:</p>
  
  <pre><code>version: '2.1'
  
  volumes:
    prometheus_data: {}
  
  services:
    prometheus:
      mem_limit: 1000m
      image: prom/prometheus
      container_name: prometheus
      volumes:
        - ./prometheus/:/etc/prometheus/
        - prometheus_data:/prometheus
      command:
        - '--config.file=/etc/prometheus/prometheus.yml'
        - '--storage.tsdb.retention.time=200h'
      links:
        - 'blackbox:blackbox'
      expose:
        - 9090
      labels:
        container_group: monitoring
  
    blackbox:
      image: prom/blackbox-exporter
      container_name: blackbox
      expose:
        - 9115
      volumes:
        - ./blackbox/:/etc/blackbox/
      command: --config.file=/etc/blackbox/blackbox.yml
      labels:
        container_group: monitoring
  </code></pre>
  
  <p>prometheus.yml</p>
  
  <pre><code>scrape_configs:
  
    - job_name: 'blackbox'
      metrics_path: /probe
      params:
        module: [http_2xx]
         file_sd_configs:
        - files: ['/blackbox/blackbox_targets.yml']
      relabel_configs:
        - source_labels: [__address__]
          target_label: __param_target
        - target_label: __address__
          replacement: blackbox:9115
  </code></pre>
  
  <p>blackbox_targets.yml</p>
  
  <pre><code>- targets: ['http://google.com']
    labels:
      group: 'localhost'
      instance: 'localhost'
  </code></pre>
  
  <p>Without blackbox_targets.yml can see targets in prometheus bat leter on are missing.</p>