code: /*
   * 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
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * 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.skywalking.oap.server.core.storage;
  
  import org.apache.skywalking.oap.server.core.analysis.TimeBucket;
  import org.apache.skywalking.oap.server.core.analysis.metrics.Metrics;
  import org.apache.skywalking.oap.server.core.storage.model.Model;
  import org.apache.skywalking.oap.server.library.client.request.InsertRequest;
  import org.apache.skywalking.oap.server.library.client.request.UpdateRequest;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  
  /**
   * Metrics related DAO.
   */
  public interface IMetricsDAO extends DAO {
      /**
       * Read data from the storage by given IDs.
       *
       * @param model   target entity of this query.
       * @param metrics metrics list.
       * @return the data of all given IDs. Only include existing data. Don't require to keep the same order of ids list.
       * @throws IOException when error occurs in data query.
       */
      List<Metrics> multiGet(Model model, List<Metrics> metrics) throws Exception;
  
      /**
       * Transfer the given metrics to an executable insert statement.
       *
       * @return InsertRequest should follow the database client driver datatype, in order to make sure it could be
       * executed ASAP.
       */
      InsertRequest prepareBatchInsert(Model model, Metrics metrics, SessionCacheCallback callback) throws IOException;
  
      /**
       * Transfer the given metrics to an executable update statement.
       *
       * @return UpdateRequest should follow the database client driver datatype, in order to make sure it could be
       * executed ASAP.
       */
      UpdateRequest prepareBatchUpdate(Model model, Metrics metrics, SessionCacheCallback callback) throws IOException;
  
      /**
       * Calculate the expired status of the metric by given current timestamp, metric and TTL.
       *
       * @param model             of the given cached value
       * @param cachedValue       is a metric instance
       * @param currentTimeMillis current system time of OAP.
       * @param ttl               from core setting.
       * @return true if the metric is expired.
       */
      default boolean isExpiredCache(Model model, Metrics cachedValue, long currentTimeMillis, int ttl) {
          final long metricTimestamp = TimeBucket.getTimestamp(
              cachedValue.getTimeBucket(), model.getDownsampling());
          // If the cached metric is older than the TTL indicated.
          return currentTimeMillis - metricTimestamp > TimeUnit.DAYS.toMillis(ttl);
      }
  
  }
  