server/src/main/java/org/apache/druid/segment/loading/SegmentCacheManager.java

/*
 * 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.druid.segment.loading;

import org.apache.druid.timeline.DataSegment;

import java.io.File;

/**
 * A class to fetch segment files to local disk and manage the local cache.
 * Implementations must be thread-safe.
 */
public interface SegmentCacheManager
{
  /**
   * Checks whether a segment is already cached.
   */
  boolean isSegmentCached(DataSegment segment);

  /**
   * This method fetches the files for the given segment if the segment is not downloaded already.
   * @throws SegmentLoadingException if there is an error in downloading files
   */
  File getSegmentFiles(DataSegment segment) throws SegmentLoadingException;

  /**
   * Cleanup the cache space used by the segment
   */
  void cleanup(DataSegment segment);
}