StorageAccount.h

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#ifndef STORAGE_FACTORY_STORAGE_ACCOUNT_H
#define STORAGE_FACTORY_STORAGE_ACCOUNT_H

#include <cstdint>
#include <string>
#include <chrono>
#include <atomic>
#include <map>
#include <memory>
#include "tbb/concurrent_unordered_map.h"

namespace edm::storage {
  class StorageAccount {
  public:
    enum class Operation {
      check,
      close,
      construct,
      destruct,
      flush,
      open,
      position,
      prefetch,
      read,
      readActual,
      readAsync,
      readPrefetchToCache,
      readViaCache,
      readv,
      resize,
      seek,
      stagein,
      stat,
      write,
      writeActual,
      writeViaCache,
      writev
    };

    struct Counter {
      Counter()
          : attempts{0},
            successes{0},
            amount{0},
            amount_square{0.},
            vector_count{0},
            vector_square{0},
            timeTotal{0.},
            timeMin{0.},
            timeMax{0.} {}

      //NOTE: This is needed by tbb::concurrent_unordered_map when it
      // is constructing a new one. This would not give correct results
      // if the object being passed were being updated, but that is not
      // the case for operator[]
      Counter(Counter const& iOther)
          : attempts{iOther.attempts.load()},
            successes{iOther.successes.load()},
            amount{iOther.amount.load()},
            amount_square{iOther.amount_square.load()},
            vector_count{iOther.vector_count.load()},
            vector_square{iOther.vector_square.load()},
            timeTotal{iOther.timeTotal.load()},
            timeMin{iOther.timeMin.load()},
            timeMax{iOther.timeMax.load()} {}

      //Use atomics to allow concurrent read/write for intermediate
      // output of the statics while running. The values obtained
      // won't be completely consistent but should be good enough for
      // monitoring. The values obtained once the program is shutting
      // down should be completely consistent.

      std::atomic<uint64_t> attempts;
      std::atomic<uint64_t> successes;
      std::atomic<uint64_t> amount;
      // NOTE: Significant risk exists for underflow in this value.
      // However, the use cases are marginal so I let it pass.
      std::atomic<double> amount_square;
      std::atomic<int64_t> vector_count;
      std::atomic<int64_t> vector_square;
      std::atomic<double> timeTotal;
      std::atomic<double> timeMin;
      std::atomic<double> timeMax;

      static void addTo(std::atomic<double>& iAtomic, double iToAdd) {
        double oldValue = iAtomic.load();
        double newValue = oldValue + iToAdd;
        while (not iAtomic.compare_exchange_weak(oldValue, newValue)) {
          newValue = oldValue + iToAdd;
        }
      }
    };

    class Stamp {
    public:
      Stamp(Counter& counter);

      void tick(uint64_t amount = 0, int64_t tick = 0) const;

    protected:
      Counter& m_counter;
      std::chrono::time_point<std::chrono::high_resolution_clock> m_start;
    };

    class StorageClassToken {
    public:
      StorageClassToken(StorageClassToken const&) = default;
      StorageClassToken() = delete;
      int value() const { return m_value; }

      friend class StorageAccount;

    private:
      explicit StorageClassToken(int iValue) : m_value{iValue} {}

      int m_value;
    };

    typedef tbb::concurrent_unordered_map<int, Counter> OperationStats;
    typedef tbb::concurrent_unordered_map<int, OperationStats> StorageStats;

    static char const* operationName(Operation operation);
    static StorageClassToken tokenForStorageClassName(std::string const& iName);
    static const std::string& nameForToken(StorageClassToken);

    static const StorageStats& summary(void);
    static std::string summaryText(bool banner = false);
    static void fillSummary(std::map<std::string, std::string>& summary);
    static Counter& counter(StorageClassToken token, Operation operation);

  private:
    static StorageStats m_stats;
  };
}  // namespace edm::storage
#endif  // STORAGE_FACTORY_STORAGE_ACCOUNT_H