health_monitor_metric_buffer.h

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/* Copyright (c) 2025, 2026, Oracle and/or its affiliates.
 
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#pragma once
 
#include <atomic>
 
#include "health_monitor_stat_buffer.h"
 
namespace hm {
 
/**
  Metric_Buffer extends the circular buffer, Stat_Buffer, with a two-way
  read/write capability such that it can be shared between multiple
  collectors.
*/
template <typename T>
class Metric_Buffer : public Stat_Buffer<T> {
 public:
  Metric_Buffer() = default;
 
  Metric_Buffer(bool no_lock, PSI_memory_key memory_key)
      : Stat_Buffer<T>(no_lock, memory_key) {}
 
  Metric_Buffer(PSI_rwlock_key rwlock_key, PSI_memory_key memory_key)
      : Stat_Buffer<T>(rwlock_key, memory_key) {}
 
  bool writeable() { return m_writeable.load(); }
  void set_writeable(bool writeable) { m_writeable.store(writeable); }
 
  // Write to the time series buffer, then set 'writeable' to false,
  // indicating that the write is complete.
  // Note that this method intentionally hides Stat_Buffer::write().
  int write(const T &record) {
    int ret = Stat_Buffer<T>::write(record);
    if (ret == 0) {
      set_writeable(false);
    }
    return ret;
  }
 
  // Provide a means to directly convert an external type U to a time series
  // type T, e.g. Disk_Info -> Disk_Metric. The method is enabled only if
  // the target type T is constructable from U.
  template <typename U>
  auto write(const U &arg)
      -> std::enable_if_t<std::is_constructible_v<T, U>, int> {
    T record(arg);
    return write(record);
  }
 
 private:
  std::atomic<bool> m_writeable{false};
};
 
}  // namespace hm