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.graph;
  
  import com.google.common.annotations.VisibleForTesting;
  import org.apache.atlas.ApplicationProperties;
  import org.apache.atlas.AtlasException;
  import org.apache.atlas.repository.RepositoryException;
  import org.apache.atlas.repository.graphdb.AtlasGraph;
  import org.apache.atlas.repository.graphdb.GraphDatabase;
  import org.apache.atlas.util.AtlasRepositoryConfiguration;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.context.annotation.Bean;
  import org.springframework.context.annotation.Configuration;
  
  /**
   * Provides access to the AtlasGraph
   *
   */
  @Configuration
  public class AtlasGraphProvider implements IAtlasGraphProvider {
      private static final Logger LOG = LoggerFactory.getLogger(AtlasGraphProvider.class);
  
      private static final String  GRAPH_REPOSITORY_MAX_RETRIES     = "atlas.graph.repository.max.retries";
      private static final String  GRAPH_REPOSITORY_RETRY_SLEEPTIME = "atlas.graph.repository.retry.sleeptime.ms";
      private static final Integer MAX_RETRY_COUNT                  = getMaxRetryCount();
      private static final Long    RETRY_SLEEP_TIME_MS              = getRetrySleepTime();
  
      private static volatile GraphDatabase<?, ?>                            graphDb;
      private static          org.apache.commons.configuration.Configuration applicationProperties;
  
      public static <V, E> AtlasGraph<V, E> getGraphInstance() {
          GraphDatabase<?, ?> db    = getGraphDatabase();
          AtlasGraph<?, ?>    graph = db.getGraph();
  
          return (AtlasGraph<V, E>) graph;
      }
  
      @VisibleForTesting
      public static void cleanup() {
          getGraphDatabase().cleanup();
      }
  
      @Override
      @Bean(destroyMethod = "")
      public AtlasGraph get() throws RepositoryException {
          try {
              return getGraphInstance();
          } catch (Exception ex) {
              LOG.info("Failed to obtain graph instance, retrying {} times, error: {}", MAX_RETRY_COUNT, ex);
  
              return retry();
          }
      }
  
      public AtlasGraph getBulkLoading() {
          try {
              GraphDatabase<?, ?> graphDB;
  
              synchronized (AtlasGraphProvider.class) {
                  Class<?> implClass = AtlasRepositoryConfiguration.getGraphDatabaseImpl();
  
                  graphDB = (GraphDatabase<?, ?>) implClass.newInstance();
              }
  
              return graphDB.getGraphBulkLoading();
          } catch (IllegalAccessException | InstantiationException e) {
              throw new RuntimeException("Error initializing graph database", e);
          }
      }
  
      private static <V, E> GraphDatabase<?, ?> getGraphDatabase() {
          try {
              GraphDatabase<?, ?> me = graphDb;
  
              if (me == null) {
                  synchronized (AtlasGraphProvider.class) {
                      me = graphDb;
  
                      if (me == null) {
                          Class<?> implClass = AtlasRepositoryConfiguration.getGraphDatabaseImpl();
  
                          me = (GraphDatabase<V, E>) implClass.newInstance();
  
                          graphDb = me;
                      }
                  }
              }
  
              return me;
          } catch (IllegalAccessException | InstantiationException e) {
              throw new RuntimeException("Error initializing graph database", e);
          }
      }
  
      private AtlasGraph retry() throws RepositoryException {
          int retryCounter = 0;
  
          while (retryCounter < MAX_RETRY_COUNT) {
              try {
                  // Retry after 30 sec to get graph instance
                  Thread.sleep(RETRY_SLEEP_TIME_MS);
  
                  return getGraphInstance();
              } catch (Exception ex) {
                  retryCounter++;
  
                  LOG.warn("Failed to obtain graph instance on attempt {} of {}", retryCounter, MAX_RETRY_COUNT, ex);
  
                  if (retryCounter >= MAX_RETRY_COUNT) {
                      LOG.info("Max retries exceeded.");
  
                      break;
                  }
              }
          }
  
          throw new RepositoryException("Max retries exceeded. Failed to obtain graph instance after " + MAX_RETRY_COUNT + " retries");
      }
  
      private static Integer getMaxRetryCount() {
          initApplicationProperties();
  
          return (applicationProperties == null) ? 3 : applicationProperties.getInt(GRAPH_REPOSITORY_MAX_RETRIES, 3);
      }
  
      private static Long getRetrySleepTime() {
          initApplicationProperties();
  
          return (applicationProperties == null) ? 30000 : applicationProperties.getLong(GRAPH_REPOSITORY_RETRY_SLEEPTIME, 30000);
      }
  
      private static void initApplicationProperties() {
          if (applicationProperties == null) {
              try {
                  applicationProperties = ApplicationProperties.get();
              } catch (AtlasException ex) {
                  // ignore
              }
          }
      }
  }
  