text: /**
   *    Copyright (C) 2018-present MongoDB, Inc.
   *
   *    This program is free software: you can redistribute it and/or modify
   *    it under the terms of the Server Side Public License, version 1,
   *    as published by MongoDB, Inc.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    Server Side Public License for more details.
   *
   *    You should have received a copy of the Server Side Public License
   *    along with this program. If not, see
   *    <http://www.mongodb.com/licensing/server-side-public-license>.
   *
   *    As a special exception, the copyright holders give permission to link the
   *    code of portions of this program with the OpenSSL library under certain
   *    conditions as described in each individual source file and distribute
   *    linked combinations including the program with the OpenSSL library. You
   *    must comply with the Server Side Public License in all respects for
   *    all of the code used other than as permitted herein. If you modify file(s)
   *    with this exception, you may extend this exception to your version of the
   *    file(s), but you are not obligated to do so. If you do not wish to do so,
   *    delete this exception statement from your version. If you delete this
   *    exception statement from all source files in the program, then also delete
   *    it in the license file.
   */
  
  #pragma once
  
  /**
   * DB usage monitor.
   */
  
  #include <boost/date_time/posix_time/posix_time.hpp>
  
  #include "mongo/db/commands.h"
  #include "mongo/db/operation_context.h"
  #include "mongo/db/stats/operation_latency_histogram.h"
  #include "mongo/util/concurrency/mutex.h"
  #include "mongo/util/string_map.h"
  
  namespace mongo {
  
  class ServiceContext;
  
  /**
   * tracks usage by collection
   */
  class Top {
  public:
      static Top& get(ServiceContext* service);
  
      Top() = default;
  
      struct UsageData {
          UsageData() : time(0), count(0) {}
          UsageData(const UsageData& older, const UsageData& newer);
          long long time;
          long long count;
  
          void inc(long long micros) {
              count++;
              time += micros;
          }
      };
  
      struct CollectionData {
          /**
           * constructs a diff
           */
          CollectionData() {}
          CollectionData(const CollectionData& older, const CollectionData& newer);
  
          UsageData total;
  
          UsageData readLock;
          UsageData writeLock;
  
          UsageData queries;
          UsageData getmore;
          UsageData insert;
          UsageData update;
          UsageData remove;
          UsageData commands;
          OperationLatencyHistogram opLatencyHistogram;
      };
  
      enum class LockType {
          ReadLocked,
          WriteLocked,
          NotLocked,
      };
  
      typedef StringMap<CollectionData> UsageMap;
  
  public:
      void record(OperationContext* opCtx,
                  StringData ns,
                  LogicalOp logicalOp,
                  LockType lockType,
                  long long micros,
                  bool command,
                  Command::ReadWriteType readWriteType);
  
      /**
       * Same as the above, but for multiple namespaces.
       */
      void record(OperationContext* opCtx,
                  const std::set<NamespaceString>& nssSet,
                  LogicalOp logicalOp,
                  LockType lockType,
                  long long micros,
                  bool command,
                  Command::ReadWriteType readWriteType);
  
      void append(BSONObjBuilder& b);
  
      void cloneMap(UsageMap& out) const;
  
      void collectionDropped(const NamespaceString& nss);
  
      /**
       * Appends the collection-level latency statistics
       */
      void appendLatencyStats(const NamespaceString& nss,
                              bool includeHistograms,
                              BSONObjBuilder* builder);
  
      /**
       * Increments the global histogram only if the operation came from a user.
       */
      void incrementGlobalLatencyStats(OperationContext* opCtx,
                                       uint64_t latency,
                                       Command::ReadWriteType readWriteType);
  
      /**
       * Increments the global transactions histogram.
       */
      void incrementGlobalTransactionLatencyStats(uint64_t latency);
  
      /**
       * Appends the global latency statistics.
       */
      void appendGlobalLatencyStats(bool includeHistograms,
                                    bool slowMSBucketsOnly,
                                    BSONObjBuilder* builder);
  
  private:
      void _appendToUsageMap(BSONObjBuilder& b, const UsageMap& map) const;
  
      void _appendStatsEntry(BSONObjBuilder& b, const char* statsName, const UsageData& map) const;
  
      void _record(OperationContext* opCtx,
                   CollectionData& c,
                   LogicalOp logicalOp,
                   LockType lockType,
                   long long micros,
                   Command::ReadWriteType readWriteType);
  
      void _incrementHistogram(OperationContext* opCtx,
                               long long latency,
                               OperationLatencyHistogram* histogram,
                               Command::ReadWriteType readWriteType);
  
      mutable SimpleMutex _lock;
      OperationLatencyHistogram _globalHistogramStats;
      UsageMap _usage;
  };
  
  }  // namespace mongo
  