tlbmc/hal/shared_mem/metrics.h

#ifndef THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_HAL_SHARED_MEM_METRICS_H_
#define THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_HAL_SHARED_MEM_METRICS_H_

#include <sys/types.h>

#include <array>
#include <atomic>
#include <cstddef>
#include <cstdint>
#include <string_view>
#include <type_traits>

#include "absl/time/time.h"
// copybara:strip_begin(g3-shared-libs)
#include "nlohmann/json.hpp"
// copybara:strip_end
#include "pattern_to_entity_array.h"

namespace milotic_tlbmc {

constexpr std::size_t kResourceCount =
    milotic::authz::pattern_entity_pair_array.size();

// clang-format off
constexpr std::array<int, 4> kSupportedStatusCodes = {
// go/keep-sorted start
  200,
  401,
  404,
  500,
// go/keep-sorted end
};
// clang-format on

constexpr size_t kResponseTimeHistogramBucketCount = 20;
constexpr absl::Duration kResponseTimeHistogramBucketTime =
    absl::Milliseconds(50);
constexpr size_t kMaxResponseStatusCode = 600;
constexpr size_t kTopLatencyResourcesCount = 20;

// The class is thread-safe.
class TlbmcMetrics {
 public:
  using MetricsIntegerType =
      std::conditional_t<sizeof(void*) == 4, uint32_t, uint64_t>;
  TlbmcMetrics() {
    static_assert(std::atomic<MetricsIntegerType>::is_always_lock_free);
  }
  // copybara:strip_begin(g3-shared-libs)
  void UpdateMetricsRequestCount(bool is_tlbmc_request);
  void UpdateMetricsResponse(absl::Duration response_time, int status_code,
                             std::string_view resource_url);
  // This call is expensive. Please call it only periodically, e.g., every
  // minute.
  nlohmann::json ToJson() const;
  // copybara:strip_end

 private:
  std::atomic<MetricsIntegerType> total_tlbmc_request_count_ = 0;
  std::atomic<MetricsIntegerType> total_gbmcweb_request_count_ = 0;
  // Response status code count.
  std::atomic<MetricsIntegerType>
      response_status_code_count_[kMaxResponseStatusCode + 1] = {0};
  // Historgram of response time. Every 50ms the response time is recorded.
  // At this moment, the histogram is 20 buckets, and each bucket is 50ms.
  // The first bucket is [0, 50ms), the last bucket is [950ms, inf).
  std::atomic<MetricsIntegerType>
      response_time_histogram_[kResponseTimeHistogramBucketCount] = {0};
  // Resource average latency distribution.
  std::atomic<MetricsIntegerType>
      total_response_count_per_resource_[kResourceCount] = {0};
  // TODO(nanzhou): handles overflow.
  std::atomic<MetricsIntegerType>
      response_total_latency_ms_per_resource_[kResourceCount] = {0};
};

}  // namespace milotic_tlbmc
#endif  // THIRD_PARTY_MILOTIC_EXTERNAL_CC_TLBMC_HAL_SHARED_MEM_METRICS_H_