code: /*
   * 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.skywalking.oap.log.analyzer.dsl.spec.sink.sampler;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicInteger;
  import lombok.EqualsAndHashCode;
  import lombok.Getter;
  import lombok.Setter;
  import lombok.experimental.Accessors;
  import lombok.extern.slf4j.Slf4j;
  
  @Accessors(fluent = true)
  @EqualsAndHashCode(of = {"rpm"})
  public class RateLimitingSampler implements Sampler {
      @Getter
      @Setter
      private volatile int rpm;
  
      private final AtomicInteger factor = new AtomicInteger();
  
      private final ResetHandler resetHandler;
  
      public RateLimitingSampler(final ResetHandler resetHandler) {
          this.resetHandler = resetHandler;
      }
  
      @Override
      public RateLimitingSampler start() {
          resetHandler.start(this);
          return this;
      }
  
      @Override
      public void close() {
          resetHandler.close(this);
      }
  
      @Override
      public boolean sample() {
          return factor.getAndIncrement() < rpm;
      }
  
      @Override
      public RateLimitingSampler reset() {
          factor.set(0);
          return this;
      }
  
      @Slf4j
      public static class ResetHandler {
          private final List<Sampler> samplers = new ArrayList<>();
  
          private volatile ScheduledFuture<?> future;
  
          private volatile boolean started = false;
  
          private synchronized void start(final Sampler sampler) {
              samplers.add(sampler);
  
              if (!started) {
                  future = Executors.newSingleThreadScheduledExecutor()
                                    .scheduleAtFixedRate(this::reset, 1, 1, TimeUnit.MINUTES);
                  started = true;
              }
          }
  
          private synchronized void close(final Sampler sampler) {
              samplers.remove(sampler);
  
              if (samplers.isEmpty() && future != null) {
                  future.cancel(true);
                  started = false;
              }
          }
  
          private synchronized void reset() {
              samplers.forEach(sampler -> {
                  try {
                      sampler.reset();
                  } catch (final Exception e) {
                      log.error("Failed to reset sampler {}.", sampler, e);
                  }
              });
          }
      }
  }
  