content: /*
   * Copyright 1999-2019 Alibaba Group Holding Ltd.
   *
   * 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.alibaba.csp.sentinel.node;
  
  /**
   * @author Eric Zhao
   * @since 1.5.0
   */
  public interface OccupySupport {
  
      /**
       * Try to occupy latter time windows' tokens. If occupy success, a value less than
       * {@code occupyTimeout} in {@link OccupyTimeoutProperty} will be return.
       *
       * <p>
       * Each time we occupy tokens of the future window, current thread should sleep for the
       * corresponding time for smoothing QPS. We can't occupy tokens of the future with unlimited,
       * the sleep time limit is {@code occupyTimeout} in {@link OccupyTimeoutProperty}.
       * </p>
       *
       * @param currentTime  current time millis.
       * @param acquireCount tokens count to acquire.
       * @param threshold    qps threshold.
       * @return time should sleep. Time >= {@code occupyTimeout} in {@link OccupyTimeoutProperty} means
       * occupy fail, in this case, the request should be rejected immediately.
       */
      long tryOccupyNext(long currentTime, int acquireCount, double threshold);
  
      /**
       * Get current waiting amount. Useful for debug.
       *
       * @return current waiting amount
       */
      long waiting();
  
      /**
       * Add request that occupied.
       *
       * @param futureTime   future timestamp that the acquireCount should be added on.
       * @param acquireCount tokens count.
       */
      void addWaitingRequest(long futureTime, int acquireCount);
  
      /**
       * Add occupied pass request, which represents pass requests that borrow the latter windows' token.
       *
       * @param acquireCount tokens count.
       */
      void addOccupiedPass(int acquireCount);
  
      /**
       * Get current occupied pass QPS.
       *
       * @return current occupied pass QPS
       */
      double occupiedPassQps();
  }
  