title: Akka-streams - how to access the materialized value of the stream
body: <p>I am learning to work with Akka streams, and really loving it, but the materialization part is still somewhat a mystery to me.</p>
  
  <p>Quoting from <a href="http://doc.akka.io/docs/akka-stream-and-http-experimental/snapshot/scala/http/client-side/host-level.html#host-level-api" rel="noreferrer">http://doc.akka.io/docs/akka-stream-and-http-experimental/snapshot/scala/http/client-side/host-level.html#host-level-api</a></p>
  
  <blockquote>
    <p>... trigger the immediate shutdown of a specific pool by calling
    shutdown() on the HostConnectionPool instance that the pool client
    flow materializes into</p>
  </blockquote>
  
  <p>How do I get hold of the HostConnectionPool instance? </p>
  
  <p>Even more importantly, I'd like to understand in general how to access the materialized value and perform some operation or retrieve information from it.</p>
  
  <p>Thanks in advance for any documentation pointers or explanation.</p>