title: What is the interaction between Solr and Zookeeper?
body: <p>I've been working on a system where they use <strong>SolrCloud</strong>, which entails a <strong>Zookeeper</strong> ensemble that helps <strong>"manage the overall structure so that both indexing and search requests can be routed properly"</strong> (straight out of the <a href="https://lucene.apache.org/solr/guide/6_6/getting-started-with-solrcloud.html" rel="noreferrer">Solr documentation</a>).</p>
  
  <p><strong>What exactly is this "management"</strong>? What information, <strong>what data</strong>/configuration/information do the machines running Solr read/write from the Zookeeper ensemble and why? Is the data in Zookeeper ever changed at runtime by solr? Or do you configure "the data" once and runtime is going to be reads all across SolrCloud hosts?</p>
  
  <p>To put the question into perspective, this is my first contact with Zookeeper, Solr, and in many ways with distributed systems.</p>