YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

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#ifndef YB_SERVER_LOGICAL_CLOCK_H_

#define YB_SERVER_LOGICAL_CLOCK_H_

#include <string>

#include "yb/server/clock.h"

#include "yb/util/status_fwd.h"

namespace yb {

class MonoDelta;

class MonoTime;

namespace server {

// An implementation of Clock that behaves as a plain Lamport Clock.  In a single node, single

// tablet, setting this generates exactly the same Timestamp sequence as the original MvccManager

// did, but it can be updated to make sure replicas generate new hybrid_times on becoming leader.

// This can be used as a deterministic hybrid_time generator that has the same consistency

// properties as a HybridTime clock.

//

// The Wait* methods are unavailable in this implementation and will return

// Status::ServiceUnavailable().

//

// NOTE: this class is thread safe.

class LogicalClock : public Clock {

 public:

  CHECKED_STATUS Init() override;

  // Returns the current value of the clock without incrementing it.

  HybridTime Peek();

  virtual void Update(const HybridTime& to_update) override;

  virtual void RegisterMetrics(const scoped_refptr<MetricEntity>& metric_entity) override;

  // Creates a logical clock whose first output value on a Now() call is 'hybrid_time'.

  static LogicalClock* CreateStartingAt(const HybridTime& hybrid_time);

 private:

  // Should use LogicalClock::CreatingStartingAt()

  explicit LogicalClock(HybridTime::val_type initial_time)

      : now_(initial_time) {}

  // Used to get the hybrid_time for metrics.

  uint64_t NowForMetrics();

  HybridTimeRange NowRange() override;

  std::atomic<uint64_t> now_;

  std::shared_ptr<void> metric_detacher_;

};

}  // namespace server

}  // namespace yb

#endif /* YB_SERVER_LOGICAL_CLOCK_H_ */