content: /*
   * 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.calcite.avatica.metrics;
  
  /**
   * General purpose factory for creating various metrics. Modeled off of the Dropwizard Metrics API.
   */
  public interface MetricsSystem {
  
    /**
     * Get or construct a {@link Timer} used to measure durations and report rates.
     *
     * @param name The name of the Timer.
     * @return An instance of {@link Timer}.
     */
    Timer getTimer(String name);
  
    /**
     * Get or construct a {@link Histogram} used to measure a distribution of values.
     *
     * @param name The name of the Histogram.
     * @return An instance of {@link Histogram}.
     */
    Histogram getHistogram(String name);
  
    /**
     * Get or construct a {@link Meter} used to measure durations and report distributions (a
     * combination of a {@link Timer} and a {@link Histogram}.
     *
     * @param name The name of the Meter.
     * @return An instance of {@link Meter}.
     */
    Meter getMeter(String name);
  
    /**
     * Get or construct a {@link Counter} used to track a mutable number.
     *
     * @param name The name of the Counter
     * @return An instance of {@link Counter}.
     */
    Counter getCounter(String name);
  
    /**
     * Register a {@link Gauge}. The Gauge will be invoked at a period defined by the implementation
     * of {@link MetricsSystem}.
     *
     * @param name The name of the Gauge.
     * @param gauge A callback to compute the current value.
     * @param <T> The type of the Gauge.
     */
    <T> void register(String name, Gauge<T> gauge);
  
  }
  
  // End MetricsSystem.java
  