title: Calling a sd_notify(0, "WATCHDOG=1") in a service
body: <p>I have a sys d service. I want to implement a watch dog for that.
  It's something like,</p>
  
  <pre><code>[Unit]
  Description=Watchdog example service
  
  [Service]
  Type=notify
  Environment=NOTIFY_SOCKET=/run/%p.sock
  ExecStartPre=-/usr/bin/docker kill %p
  ExecStartPre=-/usr/bin/docker rm %p
  ExecStart=/usr/libexec/sdnotify-proxy /run/%p.sock /usr/bin/docker run \
      --env=NOTIFY_SOCKET=/run/%p.sock \
      --name %p pranav93/test_watchdogged python hello.py
  ExecStop=/usr/bin/docker stop %p
  
  Restart=on-success
  WatchdogSec=30s
  RestartSec=30s
  
  
  [Install]
  WantedBy=multi-user.target
  </code></pre>
  
  <p>According to docs I've to call <code>sd_notify("watchdog=1")</code> every half of the interval specified (In this case it's <code>15s</code>). But I've no idea how to call that function in a service. Help would be highly appreciated.</p>