title: Getting list of running containers from a cluster
body: <p>I am running docker containers on an AWS via ECS. I have setup a cluster with some basic configuration.</p>
  
  <p>Now I am looking forward to get no. of all running containers on this cluster (spread across 2-3 EC2 instances)? Does AWS / Docker provide any API for this?</p>
  
  <p>I know on a container instance, doing <code>docker ps -a</code> will return me list of all running / stopped containers, while <code>docker ps</code> will return running containers on one system. But I want an API (which can be called from outside) or command (which I can run on any of the instance part of the cluster) and it shows me total number of running containers across cluster?</p>