io.druid.query.lookup.LookupSnapshotTaker Maven / Gradle / Ivy

/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.query.lookup;


import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import io.druid.guice.annotations.Json;
import io.druid.java.util.common.ISE;
import io.druid.java.util.common.logger.Logger;

import java.io.File;
import java.io.IOException;
import java.util.Collections;
import java.util.List;


public class LookupSnapshotTaker
{
  private static final Logger LOGGER = new Logger(LookupSnapshotTaker.class);
  protected static final String PERSIST_FILE_NAME = "lookupSnapshot.json";

  private final ObjectMapper objectMapper;
  private final File persistDirectory;
  private final File persistFile;


  public LookupSnapshotTaker(
      final @Json ObjectMapper jsonMapper,
      String persistDirectory
  )
  {
    this.objectMapper = jsonMapper;
    Preconditions.checkArgument(!Strings.isNullOrEmpty(persistDirectory), "can not work without specifying persistDirectory");
    this.persistDirectory = new File(persistDirectory);
    if (!this.persistDirectory.exists()) {
      Preconditions.checkArgument(this.persistDirectory.mkdirs(), "Oups was not able to create persist directory");
    }
    if (!this.persistDirectory.isDirectory()) {
      throw new ISE("Can only persist to directories, [%s] wasn't a directory", persistDirectory);
    }
    this.persistFile = new File(persistDirectory, PERSIST_FILE_NAME);
  }

  public synchronized List pullExistingSnapshot()
  {
    List lookupBeanList;
    try {
      if (!persistFile.isFile()) {
        LOGGER.warn("could not find any snapshot file under working directory [%s]", persistDirectory);
        return Collections.emptyList();
      } else if (persistFile.length() == 0) {
        LOGGER.warn("found empty file no lookups to load from [%s]", persistFile.getAbsolutePath());
        return Collections.emptyList();
      }
      lookupBeanList = objectMapper.readValue(persistFile, new TypeReference>(){});
      return lookupBeanList;
    }
    catch (IOException e) {
      throw new ISE(e, "Exception during reading lookups from [%s]", persistFile.getAbsolutePath());
    }
  }

  public synchronized void takeSnapshot(List lookups)
  {
    try {
       objectMapper.writeValue(persistFile, lookups);
    }
    catch (IOException e) {
      throw new ISE(e, "Exception during serialization of lookups using file [%s]", persistFile.getAbsolutePath());
    }
  }

  public File getPersistFile()
  {
    return persistFile;
  }
}