[config] add sniffedNodesFilterPath option (#559)

docs/configuration.asciidoc

@@ -181,6 +181,11 @@ Defaults:::
 Default::: If all of the hosts/host passed to the client via configuration use the same protocol then this defaults to that protocol, otherwise it defaults to `"http"`.
 
 
+`sniffedNodesFilterPath`[[config-sniffed-filter-path]]:: `String` -- Defines the https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#common-options-response-filtering:`filter_path` used when fetching the node list from Elasticsearch.
+
+Default::: `'nodes.*.http.publish_address,nodes.*.name,nodes.*.hostname,nodes.*.host,nodes.*.version'`
+
+
 `ssl`[[config-ssl]]:: `Object` -- An object defining HTTPS/SSL configuration to use for all nodes. The properties of this mimic the options accepted by http://nodejs.org/docs/latest/api/tls.html#tls_tls_connect_port_host_options_callback[`tls.connect()`] with the exception of `rejectUnauthorized`, which defaults to `false` allowing self-signed certificates to work out-of-the-box.
 +
 Additional information available in <<auth-reference>>.

src/lib/transport.js

@@ -73,6 +73,18 @@ function Transport(config) {
     self.sniffedNodesProtocol = findCommonProtocol(self.connectionPool.getAllHosts()) || null;
   }
 
+  if (config.hasOwnProperty('sniffedNodesFilterPath')) {
+    self.sniffedNodesFilterPath = config.sniffedNodesFilterPath;
+  } else {
+    self.sniffedNodesFilterPath = [
+      'nodes.*.http.publish_address',
+      'nodes.*.name',
+      'nodes.*.hostname',
+      'nodes.*.host',
+      'nodes.*.version',
+    ].join(',');
+  }
+
   if (config.sniffOnStart) {
     self.sniff();
   }
@@ -396,21 +408,14 @@ Transport.prototype.sniff = function (cb) {
   const nodesToHostCallback = this.nodesToHostCallback;
   const log = this.log;
   const sniffedNodesProtocol = this.sniffedNodesProtocol;
+  const sniffedNodesFilterPath = this.sniffedNodesFilterPath;
 
   // make cb a function if it isn't
   cb = typeof cb === 'function' ? cb : _.noop;
 
   this.request({
     path: this.sniffEndpoint,
-    query: {
-      filter_path: [
-        'nodes.*.http.publish_address',
-        'nodes.*.name',
-        'nodes.*.hostname',
-        'nodes.*.host',
-        'nodes.*.version',
-      ].join(','),
-    },
+    query: { filter_path: sniffedNodesFilterPath },
     method: 'GET'
   }, function (err, resp, status) {
     if (!err && resp && resp.nodes) {