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"
 
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;
};
 
#endif  // STORAGE_FACTORY_STORAGE_ACCOUNT_H