com.twitter.heron.api.metric.MeanReducer Maven / Gradle / Ivy

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// Copyright 2017 Twitter. All rights reserved.
//
// Licensed 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.

/**
 * 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 com.twitter.heron.api.metric;

public class MeanReducer implements IReducer {
  public MeanReducerState init() {
    return new MeanReducerState();
  }

  public MeanReducerState reduce(MeanReducerState acc, Number input) {
    acc.count++;
    acc.sum += input.doubleValue();
    return acc;
  }

  public Double extractResult(MeanReducerState acc) {
    if (acc.count > 0) {
      return acc.sum / (double) acc.count;
    } else {
      return null;
    }
  }
}