content: /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   * <p>
   * http://www.apache.org/licenses/LICENSE-2.0
   * <p>
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.atlas.repository.graphdb.janus.migration;
  
  import org.apache.atlas.utils.LruCache;
  import org.apache.tinkerpop.gremlin.structure.Graph;
  import org.apache.tinkerpop.gremlin.structure.Vertex;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Map;
  
  import static org.apache.atlas.repository.Constants.VERTEX_ID_IN_IMPORT_KEY;
  
  public class MappedElementCache {
      private static final Logger LOG = LoggerFactory.getLogger(MappedElementCache.class);
  
      final Map<Object, Vertex> lruVertexCache = new LruCache<>(500, 100000);
  
      public Vertex getMappedVertex(Graph gr, Object key) {
          try {
              Vertex ret = lruVertexCache.get(key);
  
              if (ret == null) {
                  synchronized (lruVertexCache) {
                      ret = lruVertexCache.get(key);
  
                      if (ret == null) {
                          ret = fetchVertex(gr, key);
                          lruVertexCache.put(key, ret);
                      }
                  }
              }
  
              return ret;
          } catch (Exception ex) {
              LOG.error("getMappedVertex: {}", key, ex);
              return null;
          }
      }
  
      public void clearAll() {
          lruVertexCache.clear();
      }
  
      Vertex fetchVertex(Graph gr, Object key) {
          try {
              return gr.traversal().V().has(VERTEX_ID_IN_IMPORT_KEY, key).next();
          } catch (Exception ex) {
              LOG.error("fetchVertex: fetchFromDB failed: {}", key);
              return null;
          }
      }
  }
  