/**
 * 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 org.apache.aurora.common.stats;

/**
 * A variable that contains information about a (possibly changing) value.
 *
 * @author William Farner
 */
interface RecordingStat<T extends Number> extends Stat<T> {

  /**
   * Called by the variable sampler when a sample is being taken.  Only calls to this method should
   * be used to store variable history.
   *
   * Note - if the sampling of this value depends on other variables, it is imperative that those
   * variables values are updated first (and available via {@link Stat#read()}.
   *
   * @return A new sample of the variable.
   */
  public T sample();
}