title: EC2 unhealthy instance
body: <p>ELB show that my instance is available in the appropriate zone but unhealthy. I'm tried to make request from this instance to his own health-check endpoint but received 503.</p>
  
  <p>curl -I public-IP:port/target-healthy-endpoint</p>
  
  <pre><code>HTTP/1.1 503 Service Temporarily Unavailable
  Date: Thu, 04 Aug 2016 17:25:10 GMT
  Connection: close
  Content-Type: text/html; charset=iso-8859-1
  </code></pre>
  
  <p>What does it mean, and where should I look? On aws doc found only this:</p>
  
  <pre><code>Solution 3: Ensure that you have healthy instances in every Availability Zone that your load balancer is configured to respond in. Verify this by looking at the HealthyHostCount in CloudWatch.
  </code></pre>