Add an IT which verifies that the RCA REST endpoint can be queried

src/test/java/com/amazon/opendistro/elasticsearch/performanceanalyzer/PerformanceAnalyzerIT.java

@@ -4,6 +4,7 @@
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import java.util.Objects;
 import org.apache.http.HttpHost;
 import org.apache.http.HttpStatus;
 import org.apache.http.util.EntityUtils;
@@ -14,7 +15,7 @@
 import org.elasticsearch.client.RestClient;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.test.rest.ESRestTestCase;
-import org.junit.AfterClass;
+import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
@@ -130,8 +131,22 @@ public void checkMetrics() throws Exception {
         });
     }
 
-    @AfterClass
-    public static void closePaClient() throws Exception {
+    @Test
+    public void testRcaIsRunning() throws Exception {
+        ensurePaAndRcaEnabled();
+        WaitFor.waitFor(() -> {
+            Request request = new Request("GET", "/_opendistro/_performanceanalyzer/rca");
+            try {
+                Response resp = paClient.performRequest(request);
+                return Objects.equals(HttpStatus.SC_OK, resp.getStatusLine().getStatusCode());
+            } catch (Exception e) { // 404, RCA context hasn't been set up yet
+                return false;
+            }
+        }, 2, TimeUnit.MINUTES);
+    }
+
+    @After
+    public void closePaClient() throws Exception {
         ESRestTestCase.closeClients();
         paClient.close();
         LOG.debug("AfterClass has run");