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/**
 * 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.hadoop.hbase.quotas;

import java.util.List;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.hbase.client.Mutation;
import org.apache.hadoop.hbase.client.Result;

/**
 * Interface that allows to check the quota available for an operation.
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public interface OperationQuota {
  public enum OperationType {
    MUTATE, GET, SCAN
  }

  /**
   * Keeps track of the average data size of operations like get, scan, mutate
   */
  public class AvgOperationSize {
    private final long[] sizeSum;
    private final long[] count;

    public AvgOperationSize() {
      int size = OperationType.values().length;
      sizeSum = new long[size];
      count = new long[size];
      for (int i = 0; i < size; ++i) {
        sizeSum[i] = 0;
        count[i] = 0;
      }
    }

    public void addOperationSize(OperationType type, long size) {
      if (size > 0) {
        int index = type.ordinal();
        sizeSum[index] += size;
        count[index]++;
      }
    }

    public long getAvgOperationSize(OperationType type) {
      int index = type.ordinal();
      return count[index] > 0 ? sizeSum[index] / count[index] : 0;
    }

    public long getOperationSize(OperationType type) {
      return sizeSum[type.ordinal()];
    }

    public void addGetResult(final Result result) {
      long size = QuotaUtil.calculateResultSize(result);
      addOperationSize(OperationType.GET, size);
    }

    public void addScanResult(final List results) {
      long size = QuotaUtil.calculateResultSize(results);
      addOperationSize(OperationType.SCAN, size);
    }

    public void addMutation(final Mutation mutation) {
      long size = QuotaUtil.calculateMutationSize(mutation);
      addOperationSize(OperationType.MUTATE, size);
    }
  }

  /**
   * Checks if it is possible to execute the specified operation. The quota will be estimated based
   * on the number of operations to perform and the average size accumulated during time.
   * @param numWrites number of write operation that will be performed
   * @param numReads number of small-read operation that will be performed
   * @param numScans number of long-read operation that will be performed
   * @throws ThrottlingException if the operation cannot be performed
   */
  void checkQuota(int numWrites, int numReads, int numScans) throws ThrottlingException;

  /** Cleanup method on operation completion */
  void close();

  /**
   * Add a get result. This will be used to calculate the exact quota and have a better short-read
   * average size for the next time.
   */
  void addGetResult(Result result);

  /**
   * Add a scan result. This will be used to calculate the exact quota and have a better long-read
   * average size for the next time.
   */
  void addScanResult(List results);

  /**
   * Add a mutation result. This will be used to calculate the exact quota and have a better
   * mutation average size for the next time.
   */
  void addMutation(Mutation mutation);

  /** @return the number of bytes available to read to avoid exceeding the quota */
  long getReadAvailable();

  /** @return the number of bytes available to write to avoid exceeding the quota */
  long getWriteAvailable();

  /** @return the average data size of the specified operation */
  long getAvgOperationSize(OperationType type);
}