title: Cannot create Elasticsearch mapping for Cassandra keyspace
body: <p>Currently, I am experimenting with Elassandra (combination of Elasticsearch and Cassandra). There I have an existing Cassandra keyspace with tables and want to create a mapping to Elasticsearch so that I can use the Elasticsearch API to search/filter the data.</p>
  
  <p>Unfortunately, it does not work and I am not sure why that is.</p>
  
  <p>First of all, I make a PUT request to the Elasticsearch HTTP endpoint to create the mapping:</p>
  
  <pre><code>{
      "settings": {
          "keyspace": "my_keyspace"
      },
      "mapping": {
          "sensordatatable": {
              "discover": ".*"
          },
          "eventtable": {
                  "discover": ".*"
          }
      }
  } 
  </code></pre>
  
  <p>Then I get this as answer:</p>
  
  <pre><code>{
      "error": {
          "root_cause": [
              {
                  "type": "settings_exception",
                  "reason": "Cannot create index, underlying keyspace requires the NetworkTopologyStrategy."
              }
          ],
          "type": "settings_exception",
          "reason": "Cannot create index, underlying keyspace requires the NetworkTopologyStrategy."
      },
      "status": 500
  }
  </code></pre>
  
  <p>In this post (<a href="https://github.com/strapdata/elassandra/issues/44#issuecomment-253055846" rel="nofollow noreferrer">https://github.com/strapdata/elassandra/issues/44#issuecomment-253055846</a>) someone also uses <code>SimpleStrategy</code> and it seems to work for him. Can someone explain me WHY I have to use <code>NetworkTopologyStrategy</code>?</p>