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.distributedlog.limiter;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import org.apache.bookkeeper.stats.Counter;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.apache.distributedlog.exceptions.OverCapacityException;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Collect rate limiter implementation, cost(RequestT), overlimit, etc. behavior.
   */
  public class ComposableRequestLimiter<RequestT> implements RequestLimiter<RequestT> {
      protected static final Logger LOG = LoggerFactory.getLogger(ComposableRequestLimiter.class);
  
      private final RateLimiter limiter;
      private final OverlimitFunction<RequestT> overlimitFunction;
      private final CostFunction<RequestT> costFunction;
      private final Counter overlimitCounter;
  
      /**
       * OverlimitFunction.
       */
      public interface OverlimitFunction<RequestT> {
          void apply(RequestT request) throws OverCapacityException;
      }
      /**
       * CostFunction.
       */
      public interface CostFunction<RequestT> {
          int apply(RequestT request);
      }
  
      public ComposableRequestLimiter(
              RateLimiter limiter,
              OverlimitFunction<RequestT> overlimitFunction,
              CostFunction<RequestT> costFunction,
              StatsLogger statsLogger) {
          checkNotNull(limiter);
          checkNotNull(overlimitFunction);
          checkNotNull(costFunction);
          this.limiter = limiter;
          this.overlimitFunction = overlimitFunction;
          this.costFunction = costFunction;
          this.overlimitCounter = statsLogger.getCounter("overlimit");
      }
  
      @Override
      public void apply(RequestT request) throws OverCapacityException {
          int permits = costFunction.apply(request);
          if (!limiter.acquire(permits)) {
              overlimitCounter.inc();
              overlimitFunction.apply(request);
          }
      }
  }
  