title: Solr replication stopped working (replicatableGeneration)
body: <p>I have a Solr master/slave setup using <a href="http://wiki.apache.org/solr/SolrReplication" rel="nofollow">replication</a>.</p>
  
  <p>However this suddenly stopped working, I'm not sure what happened.</p>
  
  <p>When I look at <code>/replication?command=details</code> on the master server, I see the following:</p>
  
  <pre><code>...
  &lt;str name="isMaster"&gt;true&lt;/str&gt;
  &lt;str name="isSlave"&gt;false&lt;/str&gt;
  &lt;long name="indexVersion"&gt;1323950636535&lt;/long&gt;
  &lt;long name="generation"&gt;16&lt;/long&gt;
  &lt;lst name="master"&gt;
    &lt;str name="confFiles"&gt;schema.xml,stopwords.txt&lt;/str&gt;
    &lt;arr name="replicateAfter"&gt;
      &lt;str&gt;optimize&lt;/str&gt;
      &lt;str&gt;startup&lt;/str&gt;
    &lt;/arr&gt;
    &lt;str name="replicationEnabled"&gt;true&lt;/str&gt;
    &lt;long name="replicatableIndexVersion"&gt;1323950636529&lt;/long&gt;
    &lt;long name="replicatableGeneration"&gt;14&lt;/long&gt;
  &lt;/lst&gt;
  ...
  </code></pre>
  
  <p>Note the difference in the <code>generation</code> and the <code>replicatableGeneration</code>.</p>
  
  <p>The slave is stuck at generation 14.<br>
  When I update the master its generation becomes 17, while the replicatableGeneration stays at 14.</p>
  
  <p>Why would these two differ, and how can I get replicatableGeneration to update?</p>