[VIVO-1865] - Add etag generation config (#3)

* Add etag generation config

* Attempt to re-add extraneous whitespace and newline violation

vivocore/conf/solrconfig.xml

@@ -903,6 +903,33 @@
      </arr>
   </requestHandler>
 
+  <!-- Update Request Handler.
+      http://wiki.apache.org/solr/UpdateXmlMessages
+      The canonical Request Handler for Modifying the Index through
+      commands specified using XML, JSON, CSV, or JAVABIN
+      Note: Since solr1.1 requestHandlers requires a valid content
+      type header if posted in the body. For example, curl now
+      requires: -H 'Content-type:text/xml; charset=utf-8'
+      To override the request content type and force a specific
+      Content-type, use the request parameter:
+        ?update.contentType=text/csv
+      This handler will pick a response format to match the input
+      if the 'wt' parameter is not explicit
+   -->
+ <requestHandler name="/update" class="solr.UpdateRequestHandler">
+   <!-- See below for information on defining
+        updateRequestProcessorChains that can be used by name
+        on each Update Request
+     -->
+     <lst name="defaults">
+        <str name="update.chain">etag</str>
+      </lst>
+   <!--
+      <lst name="defaults">
+        <str name="update.chain">dedupe</str>
+      </lst>
+      -->
+ </requestHandler>
 
   <initParams path="/update/**,/query,/select,/tvrh,/elevate,/spell,/browse,update">
     <lst name="defaults">
@@ -1477,6 +1504,21 @@
     </updateRequestProcessorChain>
   -->
 
+  <!-- ETag generation
+     Creates the "etag" field on the fly based on a hash of all other
+     fields.
+  -->
+   <updateRequestProcessorChain name="etag">
+     <processor class="solr.processor.SignatureUpdateProcessorFactory">
+       <bool name="enabled">true</bool>
+       <str name="signatureField">etag</str>
+       <bool name="overwriteDupes">false</bool>
+       <str name="signatureClass">solr.processor.Lookup3Signature</str>
+     </processor>
+     <processor class="solr.LogUpdateProcessorFactory" />
+     <processor class="solr.RunUpdateProcessorFactory" />
+   </updateRequestProcessorChain>
+
   <!-- Response Writers
 
        http://wiki.apache.org/solr/QueryResponseWriter