ATLAS-3368: log warning for references without relationship-def

docs/src/site/twiki/Configuration.twiki

@@ -186,6 +186,10 @@ atlas.webserver.keepalivetimesecs=60
 
 # Queue size for the requests(when max threads are busy) for the atlas web server
 atlas.webserver.queuesize=100
+
+# Set to the property to true to enable warn on no relationships defined between entities on a particular attribute
+# Not having relationships defined can lead to performance loss while adding new entities
+atlas.relationships.warnOnNoRelationships=false
 </verbatim>
 
 ---+++ Recording performance metrics

intg/src/main/java/org/apache/atlas/AtlasConfiguration.java

@@ -53,6 +53,8 @@ public enum AtlasConfiguration {
 
     GRAPHSTORE_INDEXED_STRING_SAFE_LENGTH("atlas.graphstore.indexed.string.safe.length", Short.MAX_VALUE),  // based on org.apache.hadoop.hbase.client.Mutation.checkRow()
 
+    RELATIONSHIP_WARN_NO_RELATIONSHIPS("atlas.relationships.warnOnNoRelationships", false),
+
     //search configuration
     SEARCH_MAX_LIMIT("atlas.search.maxlimit", 10000),
     SEARCH_DEFAULT_LIMIT("atlas.search.defaultlimit", 100),

repository/src/main/java/org/apache/atlas/repository/store/graph/v2/EntityGraphMapper.java

@@ -110,6 +110,7 @@ public class EntityGraphMapper {
 
     private static final String SOFT_REF_FORMAT               = "%s:%s";
     private static final int INDEXED_STR_SAFE_LEN             = AtlasConfiguration.GRAPHSTORE_INDEXED_STRING_SAFE_LENGTH.getInt();
+    private static final boolean WARN_ON_NO_RELATIONSHIP       = AtlasConfiguration.RELATIONSHIP_WARN_NO_RELATIONSHIPS.getBoolean();
     private static final String CLASSIFICATION_NAME_DELIMITER = "|";
 
     private final GraphHelper               graphHelper = GraphHelper.getInstance();
@@ -948,9 +949,9 @@ public class EntityGraphMapper {
                 }
             } else {
                 // use legacy way to create/update edges
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("No RelationshipDef defined between {} and {} on attribute: {}",  getTypeName(entityVertex),
-                               getTypeName(attributeVertex), attributeName);
+                if (WARN_ON_NO_RELATIONSHIP || LOG.isDebugEnabled()) {
+                    LOG.warn("No RelationshipDef defined between {} and {} on attribute: {}. This can lead to severe performance degradation.",
+                             getTypeName(entityVertex), getTypeName(attributeVertex), attributeName);
                 }
 
                 ret = mapObjectIdValue(ctx, context);