text: /*
   * 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.pig.backend.hadoop.executionengine.mapReduceLayer;
  
  import org.apache.hadoop.mapreduce.Job;
  import org.apache.pig.classification.InterfaceAudience;
  import org.apache.pig.classification.InterfaceStability;
  
  import java.io.IOException;
  
  /**
   * Interface to implement when you want to use a custom approach to estimating
   * the number of reducers for a job.
   *
   * @see InputSizeReducerEstimator
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public interface PigReducerEstimator {
  
      static final String BYTES_PER_REDUCER_PARAM = "pig.exec.reducers.bytes.per.reducer";
      static final String MAX_REDUCER_COUNT_PARAM = "pig.exec.reducers.max";
  
      static final long DEFAULT_BYTES_PER_REDUCER = 1000 * 1000 * 1000;
      static final int DEFAULT_MAX_REDUCER_COUNT_PARAM = 999;
  
      /**
       * Estimate the number of reducers for a given job based on the collection
       * of load funcs passed.
       *
       * @param job job instance
       * @param mapReduceOper map reducer operator of the job
       * @return the number of reducers to use, or -1 if the count couldn't be estimated
       * @throws IOException
       */
      public int estimateNumberOfReducers(Job job, MapReduceOper mapReduceOper) throws IOException;
  }
  