ATLAS-2062: Add flag to disable v1 gremlin search API using atlas-application property

distro/src/conf/atlas-application.properties

@@ -252,6 +252,11 @@ atlas.metric.query.cache.ttlInSecs=900
 #Set to false to disable full text search.
 #atlas.search.fulltext.enable=true
 
+#########  Gremlin Search Configuration  #########
+
+#Set to false to disable gremlin search.
+atlas.search.gremlin.enable=false
+
 
 ########## Add http headers ###########
 

webapp/src/main/java/org/apache/atlas/web/resources/MetadataDiscoveryResource.java

@@ -28,6 +28,7 @@ import org.apache.atlas.query.QueryParams;
 import org.apache.atlas.utils.AtlasPerfTracer;
 import org.apache.atlas.utils.ParamChecker;
 import org.apache.atlas.web.util.Servlets;
+import org.apache.commons.configuration.Configuration;
 import org.codehaus.jettison.json.JSONArray;
 import org.codehaus.jettison.json.JSONException;
 import org.codehaus.jettison.json.JSONObject;
@@ -66,6 +67,10 @@ public class MetadataDiscoveryResource {
 
     private final DiscoveryService discoveryService;
 
+    private final  boolean       gremlinSearchEnabled;
+    private static Configuration applicationProperties          = null;
+    private static final String  ENABLE_GREMLIN_SEARCH_PROPERTY = "atlas.search.gremlin.enable";
+
     /**
      * Created by the Guice ServletModule and injected with the
      * configured DiscoveryService.
@@ -73,8 +78,10 @@ public class MetadataDiscoveryResource {
      * @param discoveryService metadata service handle
      */
     @Inject
-    public MetadataDiscoveryResource(DiscoveryService discoveryService) {
+    public MetadataDiscoveryResource(DiscoveryService discoveryService, Configuration configuration) {
         this.discoveryService  = discoveryService;
+        applicationProperties  = configuration;
+        gremlinSearchEnabled   = applicationProperties != null && applicationProperties.getBoolean(ENABLE_GREMLIN_SEARCH_PROPERTY, false);
     }
 
     /**
@@ -212,6 +219,10 @@ public class MetadataDiscoveryResource {
                 perf = AtlasPerfTracer.getPerfTracer(PERF_LOG, "MetadataDiscoveryResource.searchUsingGremlinQuery(" + gremlinQuery + ")");
             }
 
+            if (!gremlinSearchEnabled) {
+                throw new DiscoveryException("Gremlin search is not enabled.");
+            }
+
             gremlinQuery = ParamChecker.notEmpty(gremlinQuery, "gremlinQuery cannot be null or empty");
             final List<Map<String, String>> results = discoveryService.searchByGremlin(gremlinQuery);