src/main/java/org/apache/gossip/manager/RingStatePersister.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.gossip.manager;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.NavigableSet;

import org.apache.gossip.LocalGossipMember;
import org.apache.log4j.Logger;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

public class RingStatePersister implements Runnable {

  private static final Logger LOGGER = Logger.getLogger(RingStatePersister.class);
  private static final ObjectMapper MAPPER = new ObjectMapper();
  private static final TypeReference<ArrayList<LocalGossipMember>> REF 
    = new TypeReference<ArrayList<LocalGossipMember>>() { };
  private GossipManager parent;
  
  public RingStatePersister(GossipManager parent){
    this.parent = parent;
  }
  
  @Override
  public void run() {
    writeToDisk();
  }
  
  File computeTarget(){
    return new File(parent.getSettings().getPathToRingState(), "ringstate." + parent.getMyself().getClusterName() + "." 
            + parent.getMyself().getId() + ".json");
  }
  
  void writeToDisk(){
    if (!parent.getSettings().isPersistRingState()){
      return;
    }
    NavigableSet<LocalGossipMember> i = parent.getMembers().keySet();
    try (FileOutputStream fos = new FileOutputStream(computeTarget())){
      MAPPER.writeValue(fos, i);
    } catch (IOException e) {
      LOGGER.debug(e);
    }
  }

  List<LocalGossipMember> readFromDisk(){
    if (!parent.getSettings().isPersistRingState()){
      return Collections.emptyList();
    }
    try (FileInputStream fos = new FileInputStream(computeTarget())){
      return MAPPER.readValue(fos, REF);
    } catch (IOException e) {
      LOGGER.debug(e);
    }
    return Collections.emptyList();
  }
  
}