Check the total node responses

Author: dnhatn

qa/mixed-cluster/src/test/java/org/elasticsearch/backwards/HotThreadsIT.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+package org.elasticsearch.backwards;
+
+import org.apache.http.util.EntityUtils;
+import org.elasticsearch.client.Request;
+import org.elasticsearch.client.Response;
+import org.elasticsearch.test.rest.ESRestTestCase;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class HotThreadsIT extends ESRestTestCase {
+
+    public void testHotThreads() throws Exception {
+        final IndexingIT.Nodes nodes = IndexingIT.buildNodeAndVersions(client());
+        final Request request = new Request("GET", "/_nodes/hot_threads");
+        final Response response = client().performRequest(request);
+        final String responseString = EntityUtils.toString(response.getEntity());
+        final String[] nodeResponses = responseString.split("::: ");
+        int respondedNodes = 0;
+        for (String nodeResponse : nodeResponses) {
+            final String[] lines = nodeResponse.split("\n");
+            final String nodeId = lines[0].trim();
+            if (nodeId.isEmpty() == false) {
+                respondedNodes++;
+            }
+        }
+        assertThat(respondedNodes, equalTo(nodes.getNewNodes().size() + nodes.getBWCNodes().size()));
+    }
+}