lucene/replicator/src/java/org/apache/lucene/replicator/Revision.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.lucene.replicator;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;

import org.apache.lucene.store.IndexInput;

/**
 * A revision comprises lists of files that come from different sources and need
 * to be replicated together to e.g. guarantee that all resources are in sync.
 * In most cases an application will replicate a single index, and so the
 * revision will contain files from a single source. However, some applications
 * may require to treat a collection of indexes as a single entity so that the
 * files from all sources are replicated together, to guarantee consistency
 * between them. For example, an application which indexes facets will need to
 * replicate both the search and taxonomy indexes together, to guarantee that
 * they match at the client side.
 * 
 * @lucene.experimental
 */
public interface Revision extends Comparable<Revision> {
  
  /**
   * Compares the revision to the given version string. Behaves like
   * {@link Comparable#compareTo(Object)}.
   */
  public int compareTo(String version);
  
  /**
   * Returns a string representation of the version of this revision. The
   * version is used by {@link #compareTo(String)} as well as to
   * serialize/deserialize revision information. Therefore it must be self
   * descriptive as well as be able to identify one revision from another.
   */
  public String getVersion();
  
  /**
   * Returns the files that comprise this revision, as a mapping from a source
   * to a list of files.
   */
  public Map<String,List<RevisionFile>> getSourceFiles();
  
  /**
   * Returns an {@link IndexInput} for the given fileName and source. It is the
   * caller's responsibility to close the {@link IndexInput} when it has been
   * consumed.
   */
  public InputStream open(String source, String fileName) throws IOException;
  
  /**
   * Called when this revision can be safely released, i.e. where there are no
   * more references to it.
   */
  public void release() throws IOException;
  
}