heron/api/src/java/com/twitter/heron/api/metric/MultiAssignableMetric.java

// Copyright 2016 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.

package com.twitter.heron.api.metric;

import java.util.HashMap;
import java.util.Map;

public class MultiAssignableMetric<T extends Number> implements IMetric<Map<String, T>> {
  private final Map<String, AssignableMetric<T>> value = new HashMap<>();
  private T initialValue;

  public MultiAssignableMetric(T initialValue) {
    this.initialValue = initialValue;
  }

  public AssignableMetric<T> scope(String key) {
    AssignableMetric<T> val = value.get(key);
    if (val == null) {
      value.put(key, val = new AssignableMetric<>(this.initialValue));
    }
    return val;
  }

  public AssignableMetric<T> safeScope(String key) {
    AssignableMetric<T> val;
    synchronized (value) {
      val = value.get(key);
      if (val == null) {
        value.put(key, val = new AssignableMetric<>(this.initialValue));
      }
    }
    return val;
  }

  @Override
  public Map<String, T> getValueAndReset() {
    Map<String, T> ret = new HashMap<>();
    synchronized (value) {
      for (Map.Entry<String, AssignableMetric<T>> e : value.entrySet()) {
        ret.put(e.getKey(), e.getValue().getValueAndReset());
      }
    }
    return ret;
  }
}