// Copyright (C) 2015 The Android Open Source Project
//
// 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.google.gerrit.metrics;

import com.google.gerrit.extensions.registration.RegistrationHandle;

/**
 * Metric whose value increments during the life of the process.
 * <p>
 * Suitable uses are "total requests handled", "bytes sent", etc.
 * Use {@link Description#setRate()} to suggest the monitoring system
 * should also track the rate of increments if this is of interest.
 * <p>
 * For an instantaneous read of a value that can change over time
 * (e.g. "memory in use") use a {@link CallbackMetric}.
 *
 * @param <F1> type of the field.
 * @param <F2> type of the field.
 * @param <F3> type of the field.
 */
public abstract class Counter3<F1, F2, F3> implements RegistrationHandle {
  /**
   * Increment the counter by one event.
   *
   * @param field1 bucket to increment.
   * @param field2 bucket to increment.
   * @param field3 bucket to increment.
   */
  public void increment(F1 field1, F2 field2, F3 field3) {
    incrementBy(field1, field2, field3, 1);
  }

  /**
   * Increment the counter by a specified amount.
   *
   * @param field1 bucket to increment.
   * @param field2 bucket to increment.
   * @param field3 bucket to increment.
   * @param value value to increment by, must be &gt;= 0.
   */
  public abstract void incrementBy(F1 field1, F2 field2, F3 field3, long value);
}